WGU Biochemistry Final Review

What does the structure of a polyunsaturated fatty acid look like?

"Poly" means many. Polyunsaturated fatty acids are fatty acids having at least two double bonds between carbons in the hydrocarbon chain.

Identify labeled parts of the following lipid molecule: 1. A-saturated fatty acid; B-unsaturated fatty acid; C-Phosphate group 2. A-Phosphate group; B-saturated fatty acid; C-unsaturated fatty acid 3. A-saturated fatty acid; B-Phosphate group; C-unsaturated fatty acid 4. A-Phosphate group; B-unsaturated fatty acid; C-saturated fatty acid

#4 A=phosphate group. It contains a phosphorus atom surrounded by four oxygens. B= unsaturated fatty acid. It is a fatty acid with one or more double bonds within the hydrocarbon chain. C=saturated fatty acid. It is a fatty acid that doesn't not contain double bonds between the carbons within the hydrocarbon chain.

Diabetic ketoacidosis can lower blood pH, which affects the structure of important proteins like hemoglobin. Which of the following interactions are most likely affected by the change in pH? Choose the letter(s) corresponding to the interaction. (a) (b) (c) (d)

(a) (b) Feedback Correct! The interactions labeled (a) are ionic bonds while (b) are hydrogen bonds. Changes in the pH can disrupt both ionic bonds and hydrogen bonds.

What is the number of oxygen molecules that must bind in order for hemoglobin to shift to the R-state (relaxed state)? 0 1 2 3 4

1 Feedback Correct! Hemoglobin's structure changes from T to R-state upon binding of one oxygen molecule.

Match the characteristics with the appropriate fatty acid. A. Saturated B. Unsaturated 1. Solid at room temperature 2. Liquid at room temperature 3. Kinked 4. Linear 5. Primarily in animal fat 6. Primarily in vegetable oils

1. A 2. B 3. B 4. A 5. B 6. A

Hemophilia is an X-linked recessive condition. This means that: 1. A person with at least one normal X chromosome without the hemophilia gene will not show signs of hemophilia 2. The disease is more common in females 3. Affected men can pass the condition on to sons but not to daughters 4. Women can only pass the condition on to daughters

1. A person with at least one normal X chromosome without the hemophilia gene will not show signs of hemophilia Feedback An X-linked recessive condition is inherited when a female has a recessive allele on each of her X chromosomes. Males inherit an X-linked recessive condition if they inherit a recessive allele on their one and only X chromosome. Therefore if a female has a dominant (or normal) allele on one of her X chromosomes, she will not have the disease. Because men only have one X-chromosome, they tend to inherit X-linked conditions more easily than females. Men with X-linked recessive conditions do not pass the disease on to their sons, because they pass a Y chromosome on to their sons. Men will pass an X chromosome to their daughters. Women are able to pass an X chromosome on to their son or their daughters.

Which of the following statements are true? (Choose all that apply) 1. As pH decreases, hemoglobin's affinity for oxygen decreases. 2. As 2,3-BPG decreases, hemoglobin's affinity for oxygen decreases. 3. As pH decreases, hemoglobin's affinity for oxygen increases. 4. As 2,3-BPG decreases, hemoglobin's affinity for oxygen increases.

1. As pH decreases, hemoglobin's affinity for oxygen decreases. 4. As 2,3-BPG decreases, hemoglobin's affinity for oxygen increases. Feedback If you chose "As pH decreases, hemoglobin's affinity for oxygen increases", the answer is incorrect. pH is positively correlated to the affinity of hemoglobin for oxygen (the Bohr effect), so as the pH decreases, the affinity will also decrease, not increase. 2,3-BPG is produced by pregnant mothers and people who live at high altitudes, and stabilizes the low affinity deoxygenated T state of hemoglobin. This makes it easier for the hemoglobin to deliver oxygen to the developing fetus or tissues that need oxygen in a high-altitude, low oxygen environment. If you chose "As 2,3-BPG decreases, hemoglobin's affinity for oxygen decreases", the answer is incorrect. 2,3-BPG is produced by pregnant mothers and people who live at high altitudes, and stabilizes the low affinity, deoxygenated T state of hemoglobin. This makes it easier for the hemoglobin to deliver oxygen to the developing fetus or tissues that need oxygen in a high-altitude, low oxygen environment. Therefore, decreasing 2,3-BPG will decrease the amount of hemoglobin in the T state, which has an overall effect of increasing hemoglobin's affinity for oxygen. pH is positively correlated to the affinity of hemoglobin for oxygen (the Bohr effect), so as the pH decreases, the affinity will also decrease.

Why is more oxygen unloaded from hemoglobin in an actively metabolizing tissue than in a resting tissue, even at the same concentration of O2? 1. At the lower pH of an actively metabolizing tissue, hemoglobin has a lower affinity for oxygen. 2. Hemoglobin binds four oxygen molecules due to a shape change caused by the lower pH of active tissues. 3. Oxygen unloaded from the hemoglobin lowers the pH, favoring the low affinity, deoxygenated T state of hemoglobin. 4. Actively metabolizing tissues use CO2, lowering the pH and favoring the low affinity deoxygenated T state of hemoglobin.

1. At the lower pH of an actively metabolizing tissue, hemoglobin has a lower affinity for oxygen. If you chose "Hemoglobin binds four oxygen molecules due to a shape change caused by the lower pH of active tissues", the answer is incorrect. Actively metabolizing tissue produces more CO2, which in turn leads to more H+ and a lower pH than tissue at rest. The Bohr effect states that hemoglobin at low pH has a low affinity for oxygen, so oxygen will be released, not bind to, hemoglobin in actively metabolizing tissues. If you chose "Oxygen unloaded from the hemoglobin lowers the pH, favoring the low affinity, deoxygenated T state of hemoglobin", the answer is incorrect. Oxygen concentration does not affect the pH. pH is a measure of the proton (H+) concentration, with high H+ resulting in low pH. CO2 does affect pH by combining with water to form bicarbonate and protons (H+); high CO2 results in high H+ and therefore low pH. If you chose "Actively metabolizing tissues use CO2, lowering the pH and favoring the low affinity deoxygenated T state of hemoglobin", the answer is incorrect. Actively metabolizing tissues generate, not use, CO2 through the breakdown of carbohydrates and fats in the citric acid cycle. Additionally, decreasing the CO2 concentration would raise the pH by producing fewer protons (H+) by carbonic anhydrase.

Which is likely to be liquid at the lowest temperature? 1. CH3(CH2)3CH=CH(CH2)2CH=CH(CH3)3COOH 2. CH3(CH2)6CH=CH(CH2)2COOH 3. CH3(CH2)16COOH 4. CH3(CH2)4CH=CH(CH2)8COOH

1. CH3(CH2)3CH=CH(CH2)2CH=CH(CH3)3COOH Feedback The fatty acid with two double bonds in the hydrocarbon chain has the most double bonds compared to the others. As the amount of double bonds within the hydrocarbon chain increases, the fluidity increases.

The amino acid at position 150 (not shown) helps to stabilize the protein by forming disulfide bonds. What amino acid is likely located at position 150? Could this amino acid form a disulfide bond with any of the amino acids in the provided sequence above? 1. Cysteine is at 150. No, Cysteine only forms a disulfide bond with itself. There are no Cysteines in the sequence above. 2. Methionine is at 150. Yes, position 10 could form a disulfide bond. 3. Either Cysteine or Methionine is at 150. Yes, position 10 could form a disulfide bond.

1. Cysteine is at 150. No, Cysteine only forms a disulfide bond with itself. There are no Cysteines in the sequence above. Feedback Correct! Disulfide bonds form only between two cysteine amino acids. The provided image is of cysteine, which would be found at position 150. There are no cysteines within the provided protein, so no disulfide bond would form between it and the cysteine at position 150.

When the wrong nucleotide is added to a newly forming DNA strand during DNA replication 1. Distortion of the double helix structure occurs because of uncomplimentary pairing of the nucleotides 2. The DNA can not be repaired 3. The cell dies 4. Thymine dimers occur

1. Distortion of the double helix structure occurs because of uncomplimentary pairing of the nucleotides Feedback Correct! A mismatch (A with C or G, T with C or G) causes a bump to form in the DNA double helix, which is recognized by proofreading enzymes and fixed by excision repair.

Select all of the following that are involved in the process of actively transcribing a gene. 1. Epigenetic modifications to nucleosomes 2. Ribosomes 3. DNA Ligase 4. Transcription Factors 5. Promoters 6. RNA polymerase 7. DNA polymerase

1. Epigenetic modifications to nucleosomes 4. Transcription Factors 5. Promoters 6. RNA polymerase Feedback Correct! Epigenetic changes result in modifications of the nucleosomes that affect chromatin packing and transcription. Transcription Factors are specialized proteins that recognize specific promoter sequences and bind to them. Once bound to the promoters, the transcription factors recruit RNA polymerase to the transcription start site. RNA polymerase begins transcribing the gene sequence into a new RNA molecule.

Which of the following are expected to occur when oxygen is not present? (Select all that apply.) 1. FADH2 levels increase, and there is a corresponding decrease in FAD. 2. The rate of the CAC increases, but the NADH and FADH2 aren't able to pass their electrons to the ETC. 3. The rate of the CAC decreases because NAD+ and FAD are not available in sufficient amounts. 4. The proton gradient dissipates, resulting in a dramatic reduction in ATP production that can lead to cell death.

1. FADH2 levels increase, and there is a corresponding decrease in FAD. 3. The rate of the CAC decreases because NAD+ and FAD are not available in sufficient amounts. 4. The proton gradient dissipates, resulting in a dramatic reduction in ATP production that can lead to cell death. Feedback Correct! Any process that requires oxygen will decrease as oxygen levels decline. The correct answer choices are: "FADH2 levels increase, and there is a corresponding decrease in FAD." Because the FADH2 will no longer be used in the Electron Transport Chain and therefore will accumulate. "The rate of the CAC decreases because NAD+ and FAD are no available in sufficient amounts." for the reason stated above. "The proton gradient dissipates, resulting in a dramatic reduction in ATP production that can lead to cell death." The proton gradient will dissipate when oxygen is not present because the electron transport chain will no longer be able to transport electrons. The proton gradient is necessary for the aerobic production of ATP.

The two amino acids below are part of the myosin protein. What interaction can these amino acids form, and where are they likely to be located in the protein? 1. Hydrophobic interaction, the core of the protein 2. Hydrophobic interaction, the surface of the protein 3. Hydrogen bond, the core of the protein 4. Hydrogen bond, the surface of the protein

1. Hydrophobic interaction, the core of the protein Feedback Correct! The two amino acids presented have side-chains comprised of only nonpolar C-C and C-H bonds. These amino acids belong to the nonpolar group and can form hydrophobic interactions. Because these amino acids cannot form hydrogen bonds they are hydrophobic in nature. This hydrophobic nature leads these amino acids to be in the interior/core of the protein, hidden away from the water surrounding the protein. If you chose "Hydrophobic interaction, the surface of the protein:" The surface of the protein is surrounded by water molecules, which do not interact favorably with nonpolar amino acid sidechains. These two amino acids will tend to be in the core of the protein instead. If you chose "Hydrogen bond, the core of the protein:" While the two amino acids shown will tend to be in the core of the protein they have nonpolarized C-C and C-H bonds that cannot participate in hydrogen bonding. If you chose "Hydrogen bond, the surface of the protein:" The two amino acids shown have nonpolarized C-C and C-H bonds that cannot participate in hydrogen bonding. These amino acids will not interact favorably with water and will tend to avoid the surface of the protein (which is surrounded by water) and instead be in the protein's core.

Which of the following contributes to the development of ketoacidosis in a diabetic patient? 1. Increased beta oxidation of fatty acids in the absence of insulin signalling 2. Decreased beta oxidation of fatty acids in the absence of insulin signalling 3. Increased gluconeogenesis in the absence of insulin signalling 4. Increased glycogenesis in the absence of insulin signalling

1. Increased beta oxidation of fatty acids in the absence of insulin signalling Feedback Correct! In the absence of insulin, beta oxidation (fatty acid breakdown) will increase. Increased fatty acid breakdown leads to buildup of acetyl-CoA, which is used to make ketone bodies (ketogenesis). Excessive amounts of ketone bodies lower blood pH, which leads to diabetic ketoacidosis.

Which of the following statements about the secondary structure of proteins is true? You may select more than one answer. 1. It involves hydrogen bonding between the backbone atoms 2. It includes alpha helices as a common form. 3. It includes beta pleated sheets as a common form. 4. It involves hydrogen bonding between amino acid side-chains.

1. It involves hydrogen bonding between the backbone atoms 2. It includes alpha helices as a common form. 3. It includes beta pleated sheets as a common form. Feedback Correct! Secondary structures arise from hydrogen bonding patterns between backbone atoms. The most common secondary structures are alpha-helices and beta sheets. Hydrogen bonding between side-chains contributes to protein tertiary structure, but not secondary structure.

Which of the following are true about a misfolded protein? You may select more than one answer. 1. It will lose its normal function. 2. It can be degraded by the cell. 3. It can be the result of denaturation. 4. It can cause protein aggregation. 5. It loses its primary structure.

1. It will lose its normal function. 2. It can be degraded by the cell. 3. It can be the result of denaturation. 4. It can cause protein aggregation. Feedback Correct! The following options are correct: "It will lose its normal function:" The function of a protein is heavily dependent on its three-dimensional shape. As a protein misfolds changes in three-dimensional shape lead the protein to lose its ability to perform its normal function. "It can be degraded by the cell:" In addition to chaperone proteins being able to help misfolded protein refold, the cell also has mechanisms for identifying and breaking down misfolded proteins into amino acids to prevent these misfolded proteins from forming aggregates. "It can be the result of denaturation:" Denaturation disrupts side chain interactions, which destabilizes tertiary structure and can cause the protein to change shape, i.e. misfold. "It can cause protein aggregation:" Misfolded proteins can have sections of hydrophobic amino acid residues exposed to water. This can lead to misfolded proteins to aggregate in order to keep these hydrophobic residues away from water.

Which of the following occur during aerobic respiration? (Choose all that apply.) 1. NADH and FADH2 are produced from NAD+ and FAD during the citric acid cycle. 2. NAD+ and FAD are produced from NADH and FADH2 during the citric acid cycle. 3. NADH and FADH2 donate electrons to the ETC, regenerating NAD+ and FAD. 4. NAD+ and FAD donate electrons to the ETC, regenerating NADH and FADH2. 5. Oxygen accepts electrons, producing water. 6. Water donates electrons to the ETC, producing oxygen.

1. NADH and FADH2 are produced from NAD+ and FAD during the citric acid cycle. 3. NADH and FADH2 donate electrons to the ETC, regenerating NAD+ and FAD. 5. Oxygen accepts electrons, producing water. Feedback If you chose the option 'NAD+ and FAD are produced from NADH and FADH2 during the citric acid cycle', the answer is incorrect. The citric acid cycle uses the NAD+ and FAD to produce NADH and FADH2. If you chose the option 'NAD+ and FAD donate electrons to the ETC, regenerating NADH and FADH2', the answer is incorrect. NAD+ and FAD do not donate electrons. Instead they will accept electrons to generate NADH and FADH2. If you chose the option 'Water donates electrons to the ETC, producing oxygen', the answer is incorrect. Water does not donate electrons to the ETC. Water is produced when O2 accepts electrons at the end of the ETC. The correct answer is 'NADH and FADH2 are produced from NAD+ and FAD during the citric acid cycle, NADH and FADH2 donate electrons to the ETC, regenerating NAD+ and FAD and oxygen accepts electrons, producing water'.

The ability to identify specific bonds and carbons of fatty acids is helpful in naming them and understanding their metabolism. Select all of the following that are true. 1. The Beta bond connects the alpha carbon to the beta carbon and is broken during beta-oxidation 2. The Alpha carbon connects the alpha carbon to the beta carbon. 3. The omega carbon at the end of the fatty acid. 4. The Beta carbon which makes this an omega 3 fatty acid

1. The Beta bond connects the alpha carbon to the beta carbon and is broken during beta-oxidation. 3. The omega carbon at the end of the fatty acid. The alpha carbon is found adjacent to the carboxylic acid group carbon. The correct answer is the beta bond, which connects the alpha carbon to the beta carbon. This is the bond that is broken during beta oxidation (which is why the pathway that breaks down fatty acids is called beta oxidation). The positions of carbons and bonds within the fatty acid chain are often named using Greek letters beginning at the carbon closest to the carboxylic acid. That is the alpha carbon, and its bond to the carbon of the carboxylic acid is called the alpha bond. Similarly, the next carbon in the chain is the beta carbon, and its bond to the alpha carbon is known as the beta bond. The carbon at the end of the fatty acid opposite the carboxylic acid group is the omega carbon. If you chose the beta carbon, the answer is incorrect. Placement of a double bond in the carbon chain determines whether the fatty acid is an omega fatty acid; The carbon at the end of the fatty acid opposite the carboxylic acid group is the omega carbon. The correct answer is the beta bond, which connects the alpha carbon to the beta carbon. This is the bond that is broken during beta oxidation (which is why the pathway that breaks down fatty acids is called beta oxidation). The positions of carbons and bonds within the fatty acid chain are often named using Greek letters beginning at the carbon closest to the carboxylic acid. That is the alpha carbon, and its bond to the carbon of the carboxylic acid is called the alpha bond. Similarly, the next carbon in the chain is the beta carbon, and its bond to the alpha carbon is known as the beta bond. The carbon at the end of the fatty acid opposite the carboxylic acid group is the omega carbon.

How do enzymes eliminate the need for high temperatures to complete a reaction? 1. The need for high temperatures is eliminated by lowering the activation energy needed for the reaction 2. The need for high temperatures is eliminated by increasing the thermal energy needed for the reaction 3. The need for high temperatures is eliminated by increasing the activation energy needed for the reaction 4. The need for high temperatures is eliminated by increasing the kinetic energy needed for the reaction

1. The need for high temperatures is eliminated by lowering the activation energy needed for the reaction Feedback Correct! The activation energy is the amount of energy the reaction needs to initiate the change of substrate into product. Without an enzyme present, this can be too much energy for the reaction to happen in the body. The enzyme lowers the amount of energy needed by positioning the right amino acids near the right substrate, so less energy is needed when the enzyme is present. Without the enzyme present, the reactive molecules would need to move fast enough and carry enough energy to hit each other with enough force to break the bonds. They would also need to hit each other in just the right orientation. The enzyme takes care of both of these issues by placing the reactive groups near each other.

CH3(CH2)4CH=CH(CH2)6COOH is an example of which type of fatty acid? (check all that apply) 1. Unsaturated fatty acid 2. Polyunsaturated fatty acid 3. Saturated fatty acid 4. Cholesterol

1. Unsaturated fatty acid Feedback Unsaturated fatty acids have at least one double bond between the carbons in the hydrocarbon chain. The correct structure is not a polyunsaturated fatty acid, but a monounsaturated fatty acid because it has only one double bond in the hydrocarbon chain. Polyunsaturated fatty acids have two or more double bonds within the hydrocarbon chain. Saturated fatty acids do not have any double bonds between the carbons in the hydrocarbon chain. Cholesterol has a tetracyclic (tetra means 4) ring structure.

GluT transporters aid in glucose transport into a cell... 1. by acting as a channel to allow transport of glucose into the cell. 2. by inhibiting the binding of insulin with insulin receptors. 3. by phosphorylating glucose and converting it to glucose-6-phosphate. 4. by assisting in the transport of insulin into the cell.

1. by acting as a channel to allow transport of glucose into the cell. Feedback Correct! GluT4 is a glucose transporter which acts as a channel that allows glucose passage into the cell. Glut4 translocation (movement) from inside of the cell to the cell surface is regulated by insulin. Insulin, which is secreted by the pancreas in response to elevated glucose levels in the blood, increases the insertion of one type of GluT, called GluT4, into the plasma membranes of most body cells, thereby increasing the rate of facilitated diffusion of glucose into those cells. This is especially evident in muscle and adipose cells. The GluT4 proteins are located on intracellular vesicles that fuse with the membrane and quickly increase the number of GluT4 transporters. This process is known as translocation of GluT4.

An enzyme that adds a phosphate group is a __________. An enzyme that removes a phosphate group is known as a _____________________. 1. kinase, phosphatase 2. phosphatase, kinase 3. kinase, hydroxylase 4. phosphatase, hydroxylase

1. kinase, phosphatase Feedback Correct! Just to help remember the difference between the two terms, think "kinases are kind and giving" and phosphatases take away phosphates.

What changes can occur to the DNA (ex. methyl groups) and to the histones that will impact gene expression? Select all that apply 1. methylation 2. chromosome replication 3. acetylation 4. splicing

1. methylation 3. acetylation Feedback Correct! Methyl groups can be added to DNA (methylation) without altering the DNA sequence. DNA methylation changes the spacing of nucleosomes. Acetyl groups can be added to histones (acetylation) and this also changes the spacing of nucleosomes. Nucleosome spacing affects the transcription of genes.

Which of the following favor the oxygenated form of hemoglobin? (select all that apply) 1. planar heme group 2. high CO2 3. Relaxed state 4. high pH 5. high H+ 6. 2,3-BPG 7. subunits are closer together

1. planar heme group 3. Relaxed state 4. high pH 7. subunits are closer together When hemoglobin binds oxygen, it is in the R-state and heme is the planar conformation. Hemoglobin binds oxygen in the lungs, where pH is high. The correct answer choices are "planar heme group, relaxed state, high pH".

Which of the following best describes the role of ATP synthase? 1. ATP synthase allows protons to flow against their concentration gradient into the matrix and generates ATP. 2. ATP synthase allows protons to flow down their concentration gradient into the matrix and generates ATP. 3. ATP synthase allows protons to flow against their concentration gradient into the intermembrane space and generates ATP. 4. ATP synthase allows protons to flow down their concentration gradient into the intermembrane space and generates ATP.

2. ATP synthase allows protons to flow down their concentration gradient into the matrix and generates ATP. Feedback Correct! ATP synthase lets protons flow out of the intermembrane space and into the matrix.

Acetyl-CoA is the starting material used to make fatty acids. Fatty acid synthesis occurs in the cell cytosol but acetyl-CoA is produced in the mitochondria and cannot be transported across the mitochondrial membrane. How does the cell overcome this issue? 1. Acetyl-CoA is converted to oxaloacetate for export out of the mitochondrion then reconverted to acetyl-CoA in the cytoplasm 2. Acetyl-CoA is converted to citric acid for export out of the mitochondrion then reconverted to acetyl-CoA in the cytoplasm 3. Acetyl-CoA is converted to fatty acids for export out of the mitochondrion then reconverted to acetyl-CoA in the cytoplasm 4. Acetyl-CoA is converted to biotin for export out of the mitochondrion then reconverted to acetyl-CoA in the cytoplasm

2. Acetyl-CoA is converted to citric acid for export out of the mitochondrion then reconverted to acetyl-CoA in the cytoplasm Feedback Correct! In the mitochondria, acetyl-CoA is converted to citrate, which is then exported and reconverted to acetyl-CoA in the cytoplasm.

Which of the following best describes the nature of protein primary structure? 1. Structural elements such as alpha helices and beta pleated sheets 2. Amino acids linked together in a specific order by peptide bonds 3. Two or more polypeptide chains coming together to form the final functional protein 4. The overall three-dimensional shape of a chain of amino acids

2. Amino acids linked together in a specific order by peptide bonds Feedback Correct! The sequence of amino acids connected by peptide bonds in a specific order defines protein primary structure. "Structural elements such as alpha helices and beta pleated sheets" refers to secondary structure. "The overall three-dimensional shape of a chain of amino acids" refers to tertiary structure. "Two or more polypeptide chains coming together to form the final functional protein" refers to quaternary structure.

Due to the Bohr effect, how will the curve below shift in response to changes in pH? 1. An increase in H+ concentration will shift hemoglobin's oxygen-binding curve to the left, while a decrease in H+ concentration will shift the curve to the right. 2. An increase in H+ concentration will shift hemoglobin's oxygen-binding curve to the right, while a decrease in H+ concentration will shift the curve to the left.

2. An increase in H+ concentration will shift hemoglobin's oxygen-binding curve to the right, while a decrease in H+ concentration will shift the curve to the left. Feedback Correct! An increase in H+ concentration lowers the pH and leads hemoglobin to be more in the T state with lower oxygen affinity, so the curve will shift right. Alternatively, a decrease in H+ concentration raises the pH and leads hemoglobin to be more in the R state with higher oxygen affinity, so the curve will shift left.

The LEP gene codes for an anorexigenic hormone. Interestingly, breastfeeding has been shown to alter methylation of the promoter of this gene, leading to increased LEP expression. What is likely happening in response to breastfeeding: 1. Breastfeeding increases the methylation of the promoter of the LEP gene, decreasing the spacing between nucleosomes. 2. Breastfeeding decreases the methylation of the promoter of the LEP gene, increasing the spacing between nucleosomes. 3. Breastfeeding decreases the methylation of the promoter of the LEP gene, decreasing the spacing between nucleosomes. 4. Breastfeeding increases the methylation of the promoter of the LEP gene, and the tight packing of the DNA alters binding of RNA polymerase.

2. Breastfeeding decreases the methylation of the promoter of the LEP gene, increasing the spacing between nucleosomes. Feedback Correct. When histones wrap up DNA, transcription will be repressed and when histones open DNA will be available for transcription.

What are differences difference between competitive and non-competitive inhibitors? 1. Competitive inhibitors bind only irreversibly to the allosteric site and do not change the enzyme tertiary structure; non-competitive inhibitors bind only irreversibly to the active site and change the enzyme tertiary structure. 2. Competitive inhibitors bind reversibly to the active site and do not change the enzyme tertiary structure; non-competitive inhibitors bind only irreversibly to the allosteric site and do not change the enzyme tertiary structure. 3. Competitive inhibitors bind reversibly to the active site and do not change the enzyme tertiary structure; non-competitive inhibitors bind reversibly or irreversibly to the allosteric site and change the enzyme tertiary structure. 4. Competitive inhibitors bind reversibly to the active site change the enzyme tertiary structure; non-competitive inhibitors bind only reversibly to the allosteric site and change the enzyme tertiary structure.

2. Competitive inhibitors bind reversibly to the active site and do not change the enzyme tertiary structure; non-competitive inhibitors bind only irreversibly to the allosteric site and do not change the enzyme tertiary structure. Feedback Correct! Competitive inhibitors bind reversibly to the active site and do not change the enzyme tertiary structure; non-competitive inhibitors bind reversibly or irreversibly to the allosteric site and change the enzyme tertiary structure. A competitive inhibitor is usually a molecule similar in structure to a substrate that can bind to an enzyme's active site even though the molecule is unable to react. This non-substrate molecule competes with the substrate for the active site. Enzymes can also be inhibited by substances called non-competitive inhibitors. Some non-competitive inhibitors attach to the enzyme at an allosteric site, which is a site other than the active site. competitive inhibitors bind to the active site. Competitive inhibitors bind to the active site so that the substrate cannot, thereby inhibiting the reaction. The presence of the non-competitive inhibitor changes the shape of the enzyme enough to interfere with binding of the normal substrate. Some non-competitive inhibitors are used in the regulation of metabolic pathways, but others are poisons. Non-competitive inhibitors distort the tertiary protein structure and alter the shape of the active site. Any enzyme molecule thus affected can no longer bind its substrate, so the enzyme cannot catalyze a reaction. Although some non-competitive inhibitors bind reversibly, others bind irreversibly and permanently inactivate the enzyme molecules, thereby greatly decreasing the reaction rate. In non-competitive inhibition, increasing the substrate concentration does not increase the reaction rate as it does in the presence of a competitive inhibitor.

Glutamine at position 16 forms an important interaction with Serine in a different location in the protein. How would the protein structure be affected if the Glutamine in position 16 were mutated to Leucine? Would this increase or decrease the stability of the protein? 1. Increase. Leucine and Serine form a stronger ionic bond together 2. Decrease. Serine and Leucine do not interact 3. Decrease. Glutamine and Serine formed a hydrogen bond that stabilized the protein structure before the mutation 4. Decrease. Glutamine and Serine formed an ionic bond that stabilized the protein structure before the mutation 5. Approximately the same. The Glutamine-Serine interaction is similar to the Leucine-Serine interaction

2. Decrease. Serine and Leucine do not interact 3. Decrease. Glutamine and Serine formed a hydrogen bond that stabilized the protein structure before the mutation Feedback Correct! Glutamine and Serine are both polar and form a hydrogen bond with each other. Leucine is hydrophobic and would not want to be near polar R group of Glutamine, therefore causing a change in the shape of the tertiary structure. This change in shape would decrease stability.

As a piece of bacon is heated in a skillet on the stove, you observe that the appearance of the bacon changes. You may even notice that the bacon becomes crispy if left in the skillet. What type of bonds or interactions in proteins are susceptible to temperature changes? Why? 1. Hydrophobic interactions. Hydrophobic interactions are oily, when the bacon grease cooks away from the bacon it takes away the hydrophobic interactions. 2. Hydrophobic interactions. As the temperature increases, as it does in the skillet, the atoms in the proteins in bacon begin to move more rapidly. This causes the hydrophobic areas of the protein to become exposed. 3. Ionic bonds. As the bacon cooks, charged amino acids become neutral causing proteins to aggregate. This aggregation causes the characteristic look of crispy bacon. 4. Disulfide bonds. Disulfide bonds are associated with the smell of cooking bacon.

2. Hydrophobic interactions. As the temperature increases, as it does in the skillet, the atoms in the proteins in bacon begin to move more rapidly. This causes the hydrophobic areas of the protein to become exposed. Feedback Correct! As the temperature increases, the atoms in the proteins begin to move more rapidly. This causes the hydrophobic areas of the protein to become exposed. The bacon has protein that undergoes this phenomenon when it is cooked.

Which of the following is incorrectly paired? 1. ATP synthesis - inner membrane of the mitochondrion 2. Lactic acid fermentation - mitochondrial matrix 3. Glycolysis - cell cytosol 4. Citric acid cycle - mitochondrial matrix

2. Lactic acid fermentation - mitochondrial matrix Feedback If you chose "ATP synthesis - inner membrane of the mitochondrion" that is incorrect. During aerobic metabolism, ATP is created during the Electron transport chain in the inner mitochondrial membrane. If you chose "Glycolysis - cell cytosol" that is incorrect. Glycolysis occurs in the cytoplasm of the cell. If you chose "Citric acid cycle - mitochondrial matrix" that is incorrect. The citric acid cycle occurs in the matrix of the mitochondria. The correct answer is "Lactic acid fermentation - mitochondrial matrix". Lactic acid fermentation occurs during anaerobic metabolism and therefore occurs in the cytosol, not the mitochondria

Which of the following components can bind directly to the iron atom in hemoglobin? (select all that apply) 1. heme 2. Oxygen 3. CO 4. CO2

2. Oxygen 3. CO Feedback Correct! Oxygen and carbon monoxide are able to bind directly to the iron atom in hemoglobin.

What is the fate of pyruvate when oxygen is absent? 1. Pyruvate is converted to acetyl-CoA and enters cellular respiration. 2. Pyruvate is converted to lactate and enters the Cori cycle. 3. Pyruvate undergoes gluconeogenesis to form glucose. 4. Pyruvate remains unchanged causing tissue levels to increase leading to cell damage.

2. Pyruvate is converted to lactate and enters the Cori cycle. Feedback Correct! Pyruvate is converted to lactate, not acetyl-CoA, when oxygen is absent.

What is the proper order of the steps involved in excision repair? 1. Recognize the damage, resynthesize the sequence, remove the damage, ligate the DNA backbone. 2. Recognize the damage, remove the damage, resynthesize the sequence, ligate the DNA backbone. 3. Recognize the damage, remove the damage, ligate the DNA backbone, resynthesize the sequence. 4. Recognize the damage, ligate the DNA backbone, remove the damage, resynthesize the sequence.

2. Recognize the damage, remove the damage, resynthesize the sequence, ligate the DNA backbone. Feedback Correct! The basic steps of excision repair are given as bullet points at the very beginning of Lesson 1: DNA and RNA; Chapter - Inheritance of Genes; Subchapter - DNA Damage and Repair; Section - Excision Repair Corrects The Most Frequent DNA Lesions.

Homologous recombination: 1. Fixes single damaged nucleotides 2. Repairs a broken chromsome using genetic information from same chromosome inherited from other parent. 3. Fixes mistakes made by DNA polymerase during DNA replication 4. Fixes multiple damaged nucleotides

2. Repairs a broken chromsome using genetic information from same chromosome inherited from other parent. Feedback Correct! Homologous refers to the pair of same chromosomes (same genes in same order, except different alleles) you inherit from each parent - for example, the two chromosome 12s in your cells, one from your mother and one from your father. Homologous recombination fixes broken chromosomes using DNA in the same position on the homologous chromosome as a template to fix the broken chromosome. Homologous recombination also shuffles DNA between the pair of chromosomes adding genetic variation.

Aggregation of proteins is the main reason behind many neurodegenerative diseases. Which one of the following mutations will likely cause a neurodegenerative disease? 1. Replacing a positively charged amino acid with a negatively charged amino acid 2. Replacing a polar amino acid with a non polar amino acid 3. Replacing a polar amino acid with another polar amino acid 4. Replacing a negatively charged amino acid with a negatively charged amino acid

2. Replacing a polar amino acid with a non polar amino acid Feedback Correct! Polar amino acids like to be around water and are usually found on the exterior of a protein. Non-polar amino acids are hydrophobic and prefer to be on the interior of a protein. Aggregation within neurodegenerative diseases is caused when non-polar amino acids become exposed on the exterior of a protein due to mutation or misfolding. In their effort to hide from water, these non-polar amino acids interact with other misfolded proteins. The misfolded proteins begin to aggregate and form long, hydrophobic fibers. These fibers cause cell death, which cause neurodegenerative diseases when this death occurs in the brain.

Frameshift mutations 1. change the number of nucleotides in a mutant gene compared to the normal gene. Examples are missense, nonsense, and silent mutations. 2. change the number of nucleotides in a mutant gene compared to the normal gene. Examples are insertion and deletion mutations. 3. change a single nucleotide in a mutant gene compared to the normal gene. Examples are insertion and deletion mutations 4. change a single nucleotide in a mutant gene compared to the normal gene. Examples are missense, nonsense, and silent mutations.

2. change the number of nucleotides in a mutant gene compared to the normal gene. Examples are insertion and deletion mutations. Feedback Correct! Mutations caused by insertion/deletions introduce a change in the 'reading frame', known as a frameshift mutation. Background: Errors that change the number of nucleotides in a gene (insertion/deletion) are said to 'shift' the 'reading frame' from the correct groups of three basses to new groups. For example, how the following can be read as CAT DOG RAT PIG APE- unless you deleted the 'C' from CAT. It then becomes, ATD OGR ATP IGA PE- which doesn't have any meaning.

Match the letters with the correct names of the processes of the central dogma (Replication; Transcription; Translation). 1. A) Transcription, B) Translation, C) Replication 2. A) Translation, B) Replication, C) Transcription 3. A) Replication, B) Transcription, C) Translation 4. A) Translation B)Transcription, Replication

3. A) Replication, B) Transcription, C) Translation Feedback Correct! The central dogma starts with DNA, which is able to be replicated to prepare for cell division. DNA in the nucleus can also be accessed and transcribed to mRNA. The mRNA will leave the nucleus and enter the cytoplasm where it will be translated into a protein by the ribosome.

The Punnett Squares below represent three different types of dominance. Which answer choice correctly identifies the different types of Dominance? 1. A. Complete Dominance; B. Incomplete Dominance; C. Codominance 2. A. Codominance; B. Complete Dominance; C. Incomplete Dominance 3. A. Incomplete Dominance; B. Complete Dominance; C. Codominance 4. A. Codominance; B. Incomplete Dominance; C. Complete Dominance

3. A. Incomplete Dominance; B. Complete Dominance; C. Codominance Feedback A. Incomplete Dominance (heterozygotes are a color in-between the dominant and recessive color). B. Complete Dominance (All flowers are completely the dominant color or the recessive color). C. Codominance (heterozygotes are both the dominant and the recessive color).

Primary structure consists of the order of ______ in a protein. These are held together with ______ bonds that are formed by a ______ reaction. 1. Nucleotides, phosphodiester, dehydration 2. Amino acids, peptide, hydrolysis 3. Amino acids, peptide, dehydration 4. Nucleotides, peptide, dehydration

3. Amino acids, peptide, dehydration Feedback Correct! Protein primary structure is defined by the order of amino acids that make up the protein. The amino acids are linked together by peptide bonds, which are formed via dehydration reactions. Dehydration reactions involve two molecules reacting to produce H2O and another product molecule. These reactions are called dehydration reactions because it is as if the two reactant molecules were dehydrated (H2O was removed from them).

It is important for fish inhabiting colder waters to maintain membrane fluidity. Which of the following fatty acids would be associated with greatest membrane fluidity? 1. CH3(CH2)5CH=CH(CH2)7COOH 2. CH3(CH2)8CH=CH(CH2)4COOH 3. CH3(CH2)3CH=CH(CH2)2CH=CH(CH2)2COOH 4. CH3(CH2)18COOH

3. CH3(CH2)3CH=CH(CH2)2CH=CH(CH2)2COOH

t is important for fish inhabiting colder waters to maintain membrane fluidity. Which of the following fatty acids would be associated with greatest membrane fluidity? 1. CH3(CH2)5CH=CH(CH2)7COOH 2. CH3(CH2)8CH=CH(CH2)4COOH 3. CH3(CH2)3CH=CH(CH2)2CH=CH(CH2)2COOH 4. CH3(CH2)18COOH

3. CH3(CH2)3CH=CH(CH2)2CH=CH(CH2)2COOH Feedback Correct! This fatty acid has the most double bonds. When you increase the amount of double bonds within the hydrocarbon chain, the fluidity increases. Note, the other structures have less or no double bonds within the hydrocarbon chain, so they are not as fluid.

Nucleotide excision repair: 1. Fixes single damaged nucleotides 2. Fixes mistakes made by DNA polymerase during DNA replication 3. Fixes multiple damaged nucleotides 4. Repairs a broken chromosome using genetic information from same chromosome inherited from other parent.

3. Fixes multiple damaged nucleotides Feedback Correct! Nucleotide excision repair replaces several damaged nucleotides.

Regulation of carbohydrate and fatty acid metabolism are connected and controlled by two hormones - insulin and glucagon. Insulin is released after a meal, when blood sugar levels are high. Which of the following pathways are stimulated by insulin? 1. Gluconeogenesis, glycogenolysis, fatty acid oxidation 2. Glycogenolysis, fatty acid oxidation, movement of GLUT4 to the cell membrane 3. Glycogenesis, fatty acid synthesis, movement of GLUT4 to the cell membrane Glycogenesis, glycogenolysis, fatty acid oxidation

3. Glycogenesis, fatty acid synthesis, movement of GLUT4 to the cell membrane Feedback Correct! Insulin stimulates glycogenesis, fatty acid synthesis, and movement of GLUT4 to the cell membrane. Insulin is released when blood sugar levels are high, to signal the body to absorb glucose and store energy. Movement of the glucose transporter, GLUT4, to the cell membrane increases uptake of glucose from the blood. Glycogenesis, making glycogen from glucose molecules, and fatty acid synthesis act to store energy.

Regulation of carbohydrate and fatty acid metabolism are connected. Both insulin and glucagon play a role in that regulation. Glucagon is released after fasting, when blood glucose is low, to stimulate glucose production and mobilize energy. Release of glucagon would decrease all of the following EXCEPT: 1. Glycogenesis 2. Fatty acid synthesis 3. Glycogenolysis 4. Triglyceride synthesis

3. Glycogenolysis Feedback Correct! Glucagon stimulates glycogenolysis to release glucose for the liver to export to the bloodstream when blood sugar is low. Glycogenesis, fatty acid synthesis, and triglyceride synthesis would all decrease because they would use up glucose and/or store energy.

Patients with carbon monoxide (CO) poisoning may exhibit pink or cherry red skin, mucus membranes and nails. Which statement accurately describes hemoglobin's role in CO poisoning? 1. Hb binds to CO with a lower affinity than oxygen and stabilizes the R-state. 2. Hb binds to CO with a higher affinity than oxygen and stabilizes the T-state. 3. Hb binds to CO with a higher affinity than oxygen and stabilizes the R-state. 4. Hb binds to CO with a lower affinity than oxygen and stabilizes the T-state.

3. Hb binds to CO with a higher affinity than oxygen and stabilizes the R-state. Feedback Correct! Hemoglobin binds 200-times more strongly to CO than oxygen and When CO binds to hemoglobin, it stabilizes the R-state of the protein. The R state of hemoglobin is responsible for the pink or cherry red color observed in CO poisoning.

A woman is about to begin her ascent of Mount Everest and is preparing for Day 1 of the climb. Approximately 6 hours before the hike begins, she and her climbing team eat a meal containing 80% complex carbohydrates. What is the physiological benefit of this approach? 1. Raising insulin levels 2. Stimulating the pancreas to release glucagon 3. Improving glycogen stores in liver and muscle 4. Increasing glycolysis in the hours leading up to the hike

3. Improving glycogen stores in liver and muscle Feedback Correct! Improving glycogen stores in liver and muscle. Glycogen is a stored form of glucose. Individual glucose units are polymerized to form glycogen and is stored in liver and muscle. People who partake in endurance sports consume complex carbohydrate meals right before the activity or sport in order to improve their glycogen stores in liver and muscle. During the activity, the stored glycogen is then broken down to supply the much needed glucose to sustain the athlete.

Which of the following statements about protein structure and stability is true? 1. Denaturation is the loss of primary, secondary, and tertiary structure 2. Denatured proteins retain their tertiary structure 3. Ionic bonds between the side chains of the charged amino acids stabilize the protein structure 4. Protein structure is not stabilized by the hydrophobic effect

3. Ionic bonds between the side chains of the charged amino acids stabilize the protein structure Feedback Correct! Ionic bonds help stabilize both the tertiary structure of a protein chain and the quaternary structure of a protein with multiple subunits.

Katrina is an 18-year-old female at Southwest High. Her high school is raising money by hosting a marathon pledge drive. She was advised to carb load before the big race. Why would this be recommended? 1. Loading on carbohydrates will decrease glucose levels. Under low glucose conditions, cells perform glycogenesis, a process of building glycogen from glucose molecules. Glycogen can then be broken down rapidly into individual glucose units when glucose is low, such as during a marathon. 2. Loading on carbohydrates will increase glucose levels. Under high glucose conditions, cells perform glycogenolysis, a process that makes glycogen from glucose molecules. Glycogen can then be broken down rapidly into individual glucose units when glucose is low, such as during a marathon. 3. Loading on carbohydrates will increase glucose levels. Under high glucose conditions, cells perform glycogenesis, a process of building glycogen from glucose molecules. Glycogen can then be broken down rapidly into individual glucose units when glucose is low, such as during a marathon. 4. None of the options are correct

3. Loading on carbohydrates will increase glucose levels. Under high glucose conditions, cells perform glycogenesis, a process of building glycogen from glucose molecules. Glycogen can then be broken down rapidly into individual glucose units when glucose is low, such as during a marathon. Feedback Correct!Loading on carbohydrates will increase glucose levels. Under high glucose conditions, cells perform glycogenesis, a process of building glycogen from glucose molecules. Glycogen can then be broken down rapidly into individual glucose units when glucose is low, such as during a marathon. An increase in carbohydrate diet, will automatically increase the glucose concentration. After meeting our bodies needs, any excess glucose is stored as glycogen. Glycogen can then be broken down into individual glucose molecules when the glucose concentrations are low, such as during a marathon.

Jason is a 17-year-old male with a glycogen storage disease. He is also planning on running the high school marathon. Should Jason consume a diet that is low in a) fats, b) protein/amino acids, or c) carbohydrates/glucose? Explain. 1. Low fat because he is unable to used store triglycerides for energy due to non-functioning enzymes. 2. Low protein since he is unable to deaminate amino acids. 3. Low carbohydrate because he is unable to use stored glycogen for a quick source of energy.

3. Low carbohydrate because he is unable to use stored glycogen for a quick source of energy. Feedback Correct!Low carbohydrate because he is unable to use stored glycogen for a quick source of energy. Glucose, fatty acids, and amino acids that are not broken down for energy are used in anabolic pathways to synthesize structural, regulatory, or storage molecules. Glucose molecules can be used to synthesize glycogen, a storage form of carbohydrate. If the body has enough glycogen, glucose can also be used to synthesize fatty acids. Fatty acids can be used to synthesize triglycerides that are stored as body fat. Amino acids can be used to synthesize the various proteins that the body needs, such as muscle proteins, enzymes, protein hormones, and blood proteins. Excess amino acids can be converted into fatty acids and stored as body fat.

Fatty acid chains can range anywhere from 4 to 36 carbons. When enzymes that are specific for breaking down a particular length of fatty acid chain are defective, fatal diseases occur. Which of the following diseases is associated with failure to breakdown fatty acids? 1. Hemophilia 2. Sickle cell disease 3. MCADD (Medium-chain acyl-CoA dehydrogenase deficiency) 4. Alzheimer's disease

3. MCADD (Medium-chain acyl-CoA dehydrogenase deficiency) Feedback Correct! MCADD is a disease that results from a defect in the beta oxidation of medium-chain fatty acids. MCADD usually presents in infants as vomiting and/or lack of energy due to their inability to utilize medium-chain fatty acids.

If all of the Arginine amino acids (position 2, 5, 6, 9 and 15) in the sequence above are mutated to Lysine, would there be a significant effect on the protein's stability? 1. Yes, Lysine and Arginine would repel one another because they are both positively charged 2. Yes, mutations always destabilize the protein 3. No, not significant, Lysine and Arginine would have all the same interactions

3. No, not significant, Lysine and Arginine would have all the same interactions Feedback If you chose the option "Yes, Lysine and Arginine would repel one another because they are both positively charged," this answer is incorrect because Arginine replaces Lysine. Since it is a replacement, the two amino acids would never interact. If you chose the option, "Yes, mutations always destabilize the protein," the answer is incorrect because mutations can sometimes have a minimal effect. The side chains of Lysine and Arginine are both long with a positive charge at the end. If Lysine is forming an ionic bond with another amino acid elsewhere in the protein, Arginine would be able to make that same ionic bond. The protein would therefore be stable, even with this mutation.

A two year old boy is found to have an autosomal recessive glycogen storage disease that prevents him from being able to fully metabolize glucose. On examination, he has an enlarged liver and bulky appearing muscles. Biopsy of both the liver and the muscles shows markedly increased amounts of glycogen compared to normal. Which of the following is TRUE? 1. His abnormal physical exam findings are because he has excessive synthesis of fatty acids and increased production of triglycerides. 2. So as to prevent too high a blood glucose level, the child's meals should be separated by 12 hours. If his parents have another child, there is a 50% risk that the child will also have the disease. 3. Since glucose can be partially but not fully metabolized, there is an increased concentration of the intermediate compounds and this causes a shift in enzymatic reactions, favoring the production of glycogen.

3. Since glucose can be partially but not fully metabolized, there is an increased concentration of the intermediate compounds and this causes a shift in enzymatic reactions, favoring the production of glycogen. Feedback Correct! If glucose can be absorbed by the liver and muscles cells but not be fully metabolized to make ATP, then the intermediate compounds will be converted into glycogen AND the child will need to rely on alternative nutritional sources for ATP production. Excessive glycogen will accumulate in the liver/muscles, increasing their size while worsening their function. Glycogen is the storage form of glucose. A defect in the glucose metabolism will affect the glycogen product or storage.

Acidosis occurs as a result of cardiac arrest. Which of the following is the theoretical reason why sodium bicarbonate might be administered to your patient during a cardiac arrest? 1. The bicarbonate acts to decrease pH, which enables hemoglobin to enter the T state and more effectively deliver oxygen to the tissues. 2. The bicarbonate acts to decrease pH, which enables hemoglobin to enter the lung and resume binding to oxygen. 3. The bicarbonate acts to increase pH, which may allow hemoglobin to transport oxygen more efficiently. 4. The bicarbonate acts to increase pH, prompting hemoglobin to shift to the R state and pick up CO2 that has accumulated during the cardiac arrest.

3. The bicarbonate acts to increase pH, which may allow hemoglobin to transport oxygen more efficiently. Feedback Correct! Solutions of a bicarbonate salt (e.g. baking soda) increase the pH of the body by binding to protons (H+) to form CO2 and water. Increasing the pH shifts hemoglobin toward the R state with higher oxygen affinity, enhancing the ability of hemoglobin to deliver oxygen.

Acidosis occurs as a result of cardiac arrest. Which of the following is the theoretical reason why sodium bicarbonate might be administered to your patient during a cardiac arrest? 1. The bicarbonate acts to decrease pH, which enables hemoglobin to enter the T state and more effectively deliver oxygen to the tissues. 2. The bicarbonate acts to decrease pH, which enables hemoglobin to enter the lung and resume binding to oxygen. 3. The bicarbonate acts to increase pH, which may allow hemoglobin to transport oxygen more efficiently. 4. The bicarbonate acts to increase pH, prompting hemoglobin to shift to the R state and pick up CO2 that has accumulated during the cardiac arrest.

3. The bicarbonate acts to increase pH, which may allow hemoglobin to transport oxygen more efficiently. Feedback Correct! The addition of bicarbonate will increase pH, which alleviates the acidosis caused by the cardiac arrest. A differential (high versus low) in pH levels is needed for hemoglobin to effectively transport oxygen in the body.

The LCT gene codes for Lactase, which is responsible for the breakdown of lactose. Which of the following statements could explain how Lactase activity is increased in the presence of lactose? 1. Lactose blocks RNA polymerase from binding the promoter sequence, facilitating transcription of the LCT gene. 2. Lactose prevents binding of transcription factors at the transcription start site of the LCT gene. 3. The presence of lactose causes nucleosomes to separate, exposing the LCT gene. 4. The presence of lactose causes nucleosomes to pack together tightly, exposing the LCT gene.

3. The presence of lactose causes nucleosomes to separate, exposing the LCT gene. Feedback Correct! In this case, the presence of lactose in the diet is an environmental stimulus. In response to this stimulus, DNA may be modified by the addition or removal of methyl groups and histones may be modified by the addition or removal of acetyl groups. These changes can alter the spacing of nucleosomes and therefore, affect gene expression.

A nonsense mutation 1. inserts or deletes nucleotides in a mutant gene compared to a normal gene. 2. causes a double-stranded break in a chromosome. 3. changes a codon to introduce a premature stop codon. 4. has no effect on an amino acid sequence.

3. changes a codon to introduce a premature stop codon. Feedback Correct! A mutation that introduces a premature stop codon is a nonsense mutation. Background: A nonsense mutation occurs when a point mutation (change in single nucleotide) changes a codon to a STOP codon- which causes the protein synthesis to prematurely terminate. For example, UGC (codes for Cys) changed to UGA (STOP) would cause the protein synthesis to stop early resulting in a truncated protein (non functional).

A missense mutation 1. inserts or deletes nucleotides in a mutant gene compared to a normal gene. 2. causes a double-stranded break in a chromosome. 3. changes a single amino acid in a protein. 4. has no effect on an amino acid sequence.

3. changes a single amino acid in a protein. Feedback Correct! A codon change that changes the amino acid that is being coded is a missense. Background: A single nucleotide change in the DNA (point mutation ) that changes a codon in the mRNA such that it codes for a different amino acid that it did before is called a missense mutation. The missense mutation changes one amino acid in the amino acid sequence of a protein. For example, changing the codon UUU (codes for Phe) to UUA (codes for Leu) is a missense mutation.

Carbonic anhydrase is an important __________ present in the red blood cells that aids in efficient transportation of carbon dioxide in the form of _________, from tissues to lungs. 1. enzyme, carbon dioxide 2. substrate, bicarbonate ions 3. enzyme, bicarbonate ions 4. chemical, carbon monoxide

3. enzyme, bicarbonate ions Feedback Correct. Carbonic anhydrase is an enzyme (its name ends with -ase) and it allows carbon dioxide to travel to the lungs in the form of bicarbonate, since carbon dioxide itself does not travel through the blood.

Histone proteins can be chemically modified by addition of an methyl group. If this causes nucleosomes to pack _________ , the process of ___________ is decreased at those DNA sites. 1. more loosely; transcription 2. more loosely; translation 3. more tightly; transcription 4. more tightly, translation

3. more tightly; transcription Feedback Correct! Changes to histone proteins or to DNA that result in tighter nucleosome packing make the DNA less available for transcription. Therefore, transcription is decreased.

If a patient is healthy and has a normal oxygen concentration in her blood, approximately how many ATP are produced for every molecule of glucose that enters the process of metabolism? 6 4 30 2

30 Feedback Correct! Since the patient has normal oxygen levels, their cells will undergo aerobic respiration. 30 ATP are generated per 1 glucose molecule as a result of aerobic respiration.

Assuming there is one copy of the target DNA sequence before PCR, how many copies of DNA are there after 5 PCR cycles? 256 6 65,536 16 32

32 Feedback Each cycles double the numbers of DNA copy. Round 1: 1->2. Round 2: 2 ->4. Round 3: 4 -> 8. Round 4: 8 ->16. Round 5: 16 ->32.

Label the lettered strands of nucleic acid below. The possible words to use in labeling strands are: Coding Strand, Non-template Strand, Non-coding Strand, Template Strand, and mRNA. Note: A and B refer to one strand of DNA; C and D refer to the other strand of DNA. 1. A) Template B) Coding C) Non-template D) Non-Coding E) mRNA 2. A) Template B) Non-coding C) Non-template D) Coding E) mRNA 3. A) Non-template B) Non-Coding C) Template D) Coding E) mRNA 4. A) Non-template B) Coding C) Template D) Non-coding E) mRNA

4. A) Non-template B) Coding C) Template D) Non-coding E) mRNA Feedback Correct! The coding and the non-template strands are the same strand (blanks A and B). The non-coding and the template strands are the same strand (blanks C and D).

Mismatch repair: 1. Repairs a broken chromsome using genetic information from same chromosome inherited from other parent. 2. Fixes single damaged nucleotides 3. Fixes multiple damaged nucleotides 4. Fixes mistakes made by DNA polymerase during DNA replication

4. Fixes mistakes made by DNA polymerase during DNA replication Feedback Correct! Mismatch repair fixes errors in DNA replication made by DNA polymerase.

There is no energy gained (and in fact energy is required) when converting pyruvate to lactate. Why is this a necessary step? 1. Lactate is required for gluconeogenesis to occur. 2. Fermentation is the only pathway that creates ATP. 3. NAD+ is required for gluconeogenesis to occur. 4. NAD+ is required for glycolysis to occur.

4. NAD+ is required for glycolysis to occur. Feedback Yes! Lactate fermentation regenerates NAD+ from NADH. NAD+ is essential for glycolysis to occur, which is the step where the 2 ATP of anaerobic metabolism are made.

Which statement describes the relationship between the pH in the lungs and peripheral tissues? 1. Relative to the lungs, the pH in the peripheral tissues is higher because the concentration of CO2 decreases. 2. Relative to the lungs, the pH in the peripheral tissues is lower because carbonic anhydrase binds protons (H+). 3. Relative to the lungs, the pH in the peripheral tissues is lower because the concentration of O2 decreases. 4. Relative to the lungs, the pH in the peripheral tissues is lower because the CO2 generated by metabolism is converted to bicarbonate, which releases protons (H+).

4. Relative to the lungs, the pH in the peripheral tissues is lower because the CO2 generated by metabolism is converted to bicarbonate, which releases protons (H+). Feedback Correct! The peripheral tissues are generating CO2 in the citric acid cycle (CAC) while consuming glucose, fatty acids, etc. The CO2 combines with water to form bicarbonate and H+ (protons). Increased H+ concentration causes the pH to drop. Therefore, the blood surrounding actively metabolizing tissues is acidic (low pH, high H+).

Which of the following statements about epigenetics is false? 1. Environmental stimuli control gene expression. 2. Gene expression is influenced by chemical modifications of the DNA and/or histone proteins. 3. Access to the promoter gene by transcription factors is affected. 4. The DNA sequence is permanently altered.

4. The DNA sequence is permanently altered. Feedback Correct! Epigenetics involves reversible changes to the DNA or to histone proteins. These changes, such as adding or removing methyl groups from DNA or acetyl groups from histone proteins, respond to environmental stimuli. Such changes can increase or decrease nucleosome spacing, which can make the promoter of a gene accessible or inaccessible. In this way, epigenetic changes influence gene expression.

Which of the following is an accurate statement about glycolysis? 1. Glycolysis is the breakdown of a glucose molecule that requires the presence of oxygen. 2. Glycolysis results in a net production of four ATP molecules. 3. All of these 4. The final products of glycolysis are two molecules of pyruvate.

4. The final products of glycolysis are two molecules of pyruvate. Feedback Correct! The final products of glycolysis are two molecules of pyruvate.

Which of the following statements about the different levels of protein structure is true? 1. Two or more polypeptides each with their own secondary structures come together to form a single larger tertiary structure of a protein 2. Peptide bonds between amino acids make up the secondary structure of a protein 3. The interactions between the side chains of the amino acids make up the secondary level structure of a protein 4. The interactions between the side chains of the amino acids make up the tertiary level structure of a protein

4. The interactions between the side chains of the amino acids make up the tertiary level structure of a protein Feedback Correct! The interactions between the side chains of the amino acids make up the tertiary level structure of a protein.

When comparing a normal and mutant gene sequence, how do you identify a frameshift mutation? 1. The number of nucleotides between the normal and mutant gene sequences is identical and the amino acid sequence is different. 2. The number of nucleotides between the normal and mutant gene sequences is identical and the amino acid sequence is identical. 3. The number of nucleotides between the normal and mutant gene sequences is different and the amino acid sequence is identical. 4. The number of nucleotides between the normal and mutant gene sequences is different and the amino acid sequence is different.

4. The number of nucleotides between the normal and mutant gene sequences is different and the amino acid sequence is different. Feedback Correct! Frameshift mutations are caused by changing the number of nucleotides in a sequence Background. Errors that increase or decrease the number of nucleotides in a gene cause frameshift mutations. The insertion of an extra base or the removal of one of the bases will change which groups of three bases that the ribosome reads when it translates the message. This is said to 'shift' the 'reading frame' from the correct groups of three bases to different groups of three. To visualize what a frameshift is, imagine you are given a string of letters and told to start at the beginning and read every group of three letters: CATDOGRATPIGAPE. You would get "cat dog rat pig ape". But if we add an extra letter, say CATDFOGRATPIGAPE, following our "read every group of three" rule, we would get "cat dfo gra tpi gap e". Shifting our 'reading frame' by adding one more letter completely changes what we read. This is similar to what happens with a frameshift mutation.

Point mutations 1. change the number of nucleotides in a mutant gene compared to the normal gene. Examples are missense, nonsense, and silent mutations. 2. change the number of nucleotides in a mutant gene compared to the normal gene. Examples are insertion and deletion mutations. 3. change a single nucleotide in a mutant gene compared to the normal gene. Examples are insertion and deletion mutations 4. change a single nucleotide in a mutant gene compared to the normal gene. Examples are missense, nonsense, and silent mutations.

4. change a single nucleotide in a mutant gene compared to the normal gene. Examples are missense, nonsense, and silent mutations. Feedback Correct! A single nucleotide change in the DNA is a point mutation. Background: A single nucleotide change in the DNA is a point mutation. For example, changing an A for a C would be a point mutation. Point mutations do not increase or decrease the number of nucleotides in a gene, and they might (missense and nonsense mutations) or might not (silent mutations) change the amino acid sequence of the protein.

A mutation in the protein A gene results in a negatively charged amino acid, Glutamate, being replaced with the nonpolar amino acid Leucine. This is an example of a _______ mutation that could potentially interrupt __________. 1. nonsense, a hydrogen bond 2. missense, a disulfide bond 3. nonsense, a hydrophobic interaction 4. missense, an ionic bond

4. missense, an ionic bond Feedback Correct! Point mutations resulting in a change in the amino acid sequence are called missense mutations. Since Glutamate is negatively charged, it likely participates in an ionic bond. Mutation to Leucine, a non-polar amino acid, would disrupt this ionic bond.

What happens to oxygenated hemoglobin as the amount of CO2 increases? 1. pH increases, Hb shifts more to the R state, oxygen affinity increases 2. pH increases, Hb shifts more to the T state, oxygen affinity decreases 3. pH decreases, Hb shifts more to the R state, oxygen affinity increases 4. pH decreases, Hb shifts more to the T state, oxygen affinity decreases

4. pH decreases, Hb shifts more to the T state, oxygen affinity decreases Feedback Correct! As the amount of CO2 increases, the CO2 combines with water to form H+ and bicarbonate. The increased H+ decreases the pH, which causes hemoglobin to shift more to the T state. Hemoglobin in the T state has a low affinity for oxygen

During DNA replication, which of the following sequences can be used as a primer for the following DNA sequence: 3' AGT GGA TCA CTA GGC TCT 5'? (Recall that DNA replication uses RNA primers whereas PCR uses DNA primers). 5' UCA CCU AGU GAU 3' 5' TCA CCT AGT GAT 3' 3' UCA CCU AGU GAU 5' 3' TCA CCT AGT GAT 5'

5' UCA CCU AGU GAU 3' Feedback Correct! During DNA replication, RNA is used as a primer for the DNA polymerase. Recall that primers are complementary and antiparallel to the strand of DNA that is being copied. The complementary RNA sequence for 3' AGT GGA TCA CTA GGC TCT 5'? is 5' UCA CCU AGU GAU CCG AGA 3'. Thus 5' UCA CCU AGU GAU 3', which is contained within the sequence above (beginning at the 5' end), could serve as a complementary primer for DNA synthesis.

Which of the following is the correct tRNA anticodon for the mRNA codon 5' GCA 3' ? 5' UGC 3' 5' CGU 3' 5' TGC 3' 5' CGT 3'

5' UGC 3' Feedback Correct. mRNA binding to tRNA is also complementary and antiparallel.

DNA polymerase can synthesize new DNA strands in which direction? 3' to 5' 5' to 3' any direction N-terminus to C-terminus

5' to 3' Feedback DNA needs a free 3' end to bind to and initiate synthesis of a DNA. It synthesizes in a 5' to 3' direction.

What is the expected probability that a child will have an autosomal dominant disease if their father is heterozygous for the allele and their mother is homozygous for the normal allele? 0% 25% 50% 100%

50% Feedback Aa X aa => 50% Aa diseased, 50% aa normal

Epigenetics. Given the following modification of the nucleosomes, discuss how the transcription and gene expression is impacted. In A the the nucleosomes are less condensed, and in B they are more tightly wound. Would A or B foster the ability to have more active transcription of genes? A (less condensed) B (tightly wound)

A (less condensed) Feedback Correct. When the histones of the nucleosomes have DNA wound tightly around them, less DNA is available to be bound and activated by transcription factors.

Which of the following contributes to membrane fluidity? (Select all that apply.) A. Unsaturated Fatty Acid B. Saturated Fatty Acid C. Cholesterol

A. Unsaturated Fatty Acid C. Cholesterol Feedback Correct! The correct answers are that unsaturated fatty acids and cholesterol can contribute to membrane fluidity.

What is anaerobic metabolism? ATP production using only substrate level phosphorylation. Production of ATP when oxygen is abundant. ATP production using only oxidative phosphorylation. Metabolism used for only anabolic reactions.

ATP production using only substrate level phosphorylation. Feedback Yes! During anaerobic metabolism, substrate-level phosphorylation (during glycolysis) is the only mechanism for making ATP.

A substrate binds to an enzyme at a specific site, which is referred to as a(n)_________________. Active site Substrate site Allosteric site Enzymatic site

Active site Feedback Correct! Imagine that the enzyme can be activated when the substrate binds in the active site.

Inhibitors that have a similar structure to a substrate of an enzyme are most likely to bind to the enzyme's ____________ and be a ____________ inhibitor. Allosteric site, Non-competitive Allosteric site, Competitive Active site, Non-competitive Active site, Competitive

Active site, Competitive Feedback Correct! Active site, Competitive Since competitive inhibitors are able to bind the active site of the enzyme in place of the substrate, competitive inhibitors often have a similar structure to the substrate.

Starting with one molecule of glucose, compare the amount of ATP made in aerobic vs anaerobic respiration. Aerobic respiration creates 2 ATP while anaerobic respiration creates a net 30 of ATP. Aerobic respiration creates 30 ATP while anaerobic respiration creates at net 4 of ATP. Aerobic respiration creates 30 ATP while anaerobic respiration creates 2 ATP. Aerobic and anaerobic respiration create equal numbers of ATP depending on the body's needs.

Aerobic respiration creates 30 ATP while anaerobic respiration creates 2 ATP. Feedback Correct! Aerobic metabolism creates many more ATP.

Which of the following factors can affect the protein folding and activity of an enzyme? Heat All of the options are correct pH Reducing agents

All of the options are correct Feedback Correct! Heat can disrupt hydrophobic interactions at the center of the protein. pH can disrupt ionic interactions, and also hydrogen bonds. Reducing agents can break disulfide bonds. All of these changes could affect the activity of the enzyme.

When Estrogen binds to the binding pocket of the Estrogen Receptor, it is stabilized by hydrogen bonds. Which amino acids listed below could stabilize the interaction with Estrogen in the binding pocket of the Estrogen Receptor? Check all that apply. Amino Acid 1 Amino Acid 3 Amino Acid 10 Amino Acid 16

Amino Acid 16 Feedback Correct! Amino acid 16 is polar, as evidenced by the -NH as part of the side chain. Polar amino acids participate in hydrogen bonds. In this case, polar amino acids within the estrogen receptor would participate in hydrogen bonds with estrogen.

Induced fit describes which of the following? An enzyme slightly changes its shape to accommodate specific substrates An enzyme changes shape drastically to accommodate all kinds of substrates A substrate changes shape to fit the enzyme A substrate bound to the enzyme undergoes a slight conformation change to form a product

An enzyme slightly changes its shape to accommodate specific substrates Feedback Correct! Enzymes have a high degree of specificity. They will bind to one specific class of molecules and usually catalyze only one type of reaction. The enzyme has the right amino acids in the right locations to be able to recognize a particular type of substrate. Imagine a baseball glove. The glove is designed to catch a baseball. It doesn't work as well for other types of balls. An enzyme recognizes the right kind of substrate (like the baseball glove recognizes the right type of ball), and it helps convert that special substrate into product. The baseball glove is open when the ball approaches the glove, and its shape changes in just the right way as it wraps itself around the ball after it enters so that the ball stays in the glove. In a similar way, an enzyme changes its shape in just the right way when a substrate enters its active site. A baseball glove can catch new baseballs, old baseballs, or ones that are made of higher- or lower-quality materials. These baseballs are very similar to each other, but they are not identical. This is similar to how an enzyme can recognize a certain type of molecule, or a class of very similar molecules that have very similar structures, but are not identical to each other.

Mutations in the FANCA gene (located on chromosome 16) can lead to Fanconi Anemia. A healthy individual inherited one mutant and one normal allele of the FANCA gene. Which of the following describes the inheritance pattern of Fanconi Anemia? Autosomal Dominant Autosomal Recessive X-linked Dominant X-linked Recessive

Autosomal Recessive Feedback Chromosome 16 is an autosome because it is a numbered chromosome. For a healthy individual to have a mutant allele, the mutant allele must be recessive.

Which of the following amino acids would you expect to find in the interior of a protein rather than on its exterior? A B C D

B Feedback Correct! Answer choice B represents a nonpolar amino acid, with a side-chain comprised of only nonpolar C-C and C-H bonds that is hydrophobic. This hydrophobic nature leads this amino acid to be in the interior of the protein, hidden away from the water surrounding the protein. If you chose A: The side-chain of this amino acid contains an O-H bond which allows it to form hydrogen bonds. This amino acid side-chain can interact favorably with water and is hydrophilic, so it can be on the surface of the protein next to water without issue. If you chose C: The side-chain of this amino acid contains an N-H bond which allows it to form hydrogen bonds. This amino acid side-chain can interact favorably with water and is hydrophilic, so it can be on the surface of the protein next to water without issue. If you chose D: The side-chain of this amino acid contains an O-H bond which allows it to form hydrogen bonds. This amino acid side-chain can interact favorably with water and is hydrophilic, so it can be on the surface of the protein next to water without issue.

Which of the following forms solids at room temperature? A. Unsaturated Fatty Acid B. Saturated Fatty Acid C. Cholesterol

B. Saturated Fatty Acid Feedback Correct! Saturated fatty acids are solids at room temperature.

Which of the following is associated with tight packing? A. Unsaturated Fatty Acid B. Saturated Fatty Acid C. Cholesterol

B. Saturated Fatty Acid Feedback Correct! Saturated fatty acids can pack tightly together.

Acetylcholinesterase Feedback Correct! Acetylcholinesterase Acetylcholinesterase is the enzyme that converts the substrate, acetylcholine, into the products, acetate and choline. Inhibition of acetylcholinesterase will decrease degradation of acetylcholine, therefore increasing the concentration of acetylcholine.

Below is a schematic showing the synthesis and degradation of acetylcholine, an important neurotransmitter. If you were to design a drug to keep the acetylcholine concentration high, where would you target a drug inhibitor? Acetylcholine Choline acetyltransferase Choline Acetylcholinesterase

Identify the following lipid based on the table provided: Arachidonic acid. A. Major constituent of cell membranes B. Omega 3 essential fatty acid C. Precursor to eicosanoids like prostaglandins D. Helps maintain membrane fluidity E. Molecules that constitute 98% of all body energy

C Feedback Correct! C is arachidonic acid. It is an unsaturated, essential fatty acid that is the precursor for eicosanoids.

Which of the following vitamins does not travel through the blood stream in the form of a lipid micelle? A C D K

C Feedback Correct! Vitamin C is not a fat soluble vitamin. Vitamins A, D, and K are fat soluble vitamins.

The acid portion of a fatty acid corresponds to which one of the following groups/molecules? COOH Glycerol Double bonds CH3

COOH

Glycolysis is the conversion of glucose to pyruvate. Is this a catabolic process or an anabolic process? Both of these None of the these Catabolic Anabolic

Catabolic Feedback Correct! A catabolic process occurs in glycolysis. Glucose is broken down into pyruvate and 2 ATP are generated.

In order to fulfill their function, proteins must fold in proper, three-dimensional conformations. Which one of the following molecules, available in a cell, is likely to help a protein fold properly? Cysteine Glycine Chaperone Polymerase

Chaperone Feedback Correct! Chaperones bind to newly made polypeptides and enable proper folding. Chaperones can also bind to misfolded proteins and work to refold them to their correct form.

What category does this amino acid belong to? Polar Charged Nonpolar

Charged Feedback If you selected polar, you are incorrect. The amino acid depicted is charged. There is a COO- group displayed as the R group of this amino acid. Polar amino acids have nitrogen and oxygen atoms at the end of their R groups, but no visible charges. If you selected charged, you are correct. The amino acid depicted is charged. There is a COO- group displayed as the R group of this amino acid with a visible charge. If you selected nonpolar, you are incorrect. The amino acid depicted is charged. There is a COO- group displayed as the R group of this amino acid. Nonpolar amino acids have carbon atoms bonded to hydrogen atoms at the end of their R groups and do not have a charge present.

Which of the following lipid structures is used to increase membrane fluidity?

Cholesterol Feedback Correct! Cholesterol can increase membrane fluidity.

You are in charge of designing a drug that inhibits the activity of a specific enzyme. An important criteria for the drug selection is to ensure that the drug directly competes with the original substrate by binding to the active site of the enzyme. Which of the following kind of inhibitor would be an ideal choice? Competitive inhibitor Non-specific inhibitor Non-competitive inhibitor Uncompetitive inhibitor

Competitive inhibitor Feedback Correct! Competitive inhibitor. A competitive inhibitor is usually a molecule similar in structure to a substrate that can bind to an enzyme's active site even though the molecule is unable to react. This non-substrate molecule competes with the substrate for the active site. When the inhibitor binds to an active site, it prevents the substrate from binding and thereby inhibits the reaction.

Which kind of interaction can the following pair of amino acids form between their side chains (R-groups)? Hydrogen bond Ionic bond Disulfide bond Hydrophobic interaction

Correct! Hydrogen bonds are made between R groups that have polar bonds within them N-H, O-H, C-O or C-N but do not display a visible charge (+/-) on their R group. If you selected Ionic, you are incorrect. Amino acids with opposite charged R groups will be attracted to each other and form an ionic bond. If you selected Disulfide, you are incorrect. This is a very specific interaction between two cystiene amino acids where their sulfur atoms (S) bond to each other covalently (S-S). If you selected Hydrophobic, you are incorrect. Hydrophobic interactions are made by amino acids that have carbon and hydrogen atoms bonded to each other on the outer-most portions of their R groups.

Gas exchange between maternal blood and fetal blood takes place in the placenta. If curve c in the following graph represents the dissociation curve of adult hemoglobin, which curve would represent the dissociation curve of fetal hemoglobin? Curve a Curve b Curve d Curve e

Curve b If you chose "Curve A", the answer is incorrect. Curve A represents myoglobin, with higher affinity for oxygen than hemoglobin and a sideways U-shaped ("hyperbolic") curve. Fetal hemoglobin will have an overall higher oxygen affinity (shifting curve to the left) than adult hemoglobin, while also having the S-shaped ("sigmoidal") curve. If you chose "Curve D", the answer is incorrect. While Curve D has the S-shaped ("sigmoidal") curve characteristic of hemoglobin, since it is to the right of Curve C, it has a lower affinity for oxygen. Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin to enhance the fetus' ability to obtain oxygen from the mother. Therefore, the fetal hemoglobin oxygen binding curve will be shifted to the left, not the right, of the adult hemoglobin curve (Curve C). If you chose "Curve E", the answer is incorrect. Curve E does not have the S-shaped (sigmoidal) curve characteristic of hemoglobin, nor does it represent high affinity oxygen binding characteristic of myoglobin.

Identify the following lipid based on the table provided: Cholesterol A. Major constituent of cell membranes B. Omega 3 essential fatty acid C. Precursor to eicosanoids like prostaglandins D. Helps maintain membrane fluidity E. Molecules that constitute 98% of all body energy

D Feedback A, B, C, and E do not represent cholesterol. D is cholesterol because the structure has a tetracyclic ring (four rings joined together).

Sickle Cell Anemia is inherited in an autosomal recessive pattern. Choose the set of chromosomes of a person that has inherited the disease. Green boxes represent normal alleles and yellow boxes represent mutant alleles. Captionless Image A. Chromosome 12 (Blue) vs. Chromosome 11 (Red) B. Chromosome X (Blue) vs. Chromosome Y (Red, Short) C. Chromosome 11 (Blue) vs. Chromosome 11 (Red w/green stripe) D. Chromosome 11 (Blue) vs. Chromosome 11 (Red w/yellow stripe)

D. Chromosome 11 (Blue) vs. Chromosome 11 (Red w/yellow stripe) Feedback This question depicts chromosomes and asks which pair represents an Autosomal Recessive inheritance pattern. Each of the chromosomes are pictured carrying an allele from each parent, which is depicted by a yellow or green box. The green box represents a normal or dominant allele, while the yellow box represents a mutant or recessive allele. An Autosomal trait will be carried on a numbered chromosome and both chromosomes should have the same number. An X-linked trait will be carried on an X-chromosome. This allows us to rule out answer choices A and B. To inherit a recessive trait, we need to inherit two recessive (or mutant alleles), which would be shown as two yellow boxes. A dominant trait can be inherited when one or two dominant alleles are present. Answer choice C depicts an Autosomal Dominant inheritance, while answer choice D is the correct answer because it depicts an Autosomal Recessive inheritance pattern.

A defect in an enzyme in the citric acid cycle causes the cycle to stop functioning. What is a possible consequence? Decreased levels of acetyl-CoA Increased levels of ATP Increased levels of NADH Decreased levels of ATP

Decreased levels of ATP Feedback Correct! Levels of ATP would decrease. If there is a defective enzyme in the citric acid cycle, the citric acid cycle will stop. It will no longer produce NADH and FADH2. Since NADH and FADH2 carry high energy electrons to the electron transport chain, which fuels the production of ATP, the level of ATP would decrease.

The following are steps involved in a polymerase chain reaction. Which is the correct order: Elongation, denaturation, and annealing Denaturation, annealing, and elongation Annealing, elongation, and denaturation Elongation, annealing, and denaturation

Denaturation, annealing, and elongation Feedback PCR uses repeated cycles of temperature to amplify particular DNA segments. In the first step, the reaction mixture is heated to separate the DNA strands (denaturation). The reaction is then cooled to allow the DNA primers, which define the sequence to be amplified, to anneal (base pair) with the template DNA. In the third step, DNA polymerase extends the DNA primers to create a copy of the target DNA sequence. Heating the reaction to stop polymerization and separate the DNA strands starts the cycle over again

A toddler mistakenly swallows a bathroom cleaning solution, containing a strong reducing agent. Which interaction is most likely to be disrupted within a glycoprotein in the lining of the toddlerʼs esophagus? Hydrogen Bond Disulfide Bond Hydrophobic interactions Ionic Bonds

Disulfide Bond Feedback Correct! Reducing agents disrupt disulfide bonds.

Identify the following lipid based on the table provided: Triglyceride A. Major constituent of cell membranes B. Omega 3 essential fatty acid C. Precursor to eicosanoids like prostaglandins D. Helps maintain membrane fluidity E. Molecules that constitute 98% of all body energy

E Feedback A, B, C, and D do not represent a triglyceride molecule. E is a triglyceride because it contains three fatty acid chains attached to a glycerol molecule.

In the figure provided below, what component of the enzymatic cycle does the number 3 depict? Enzyme and Product Active site Enzyme-Substrate Complex Enzyme-Product Complex

Enzyme-Product Complex Feedback Correct! The identities for each of the numbers are: 1) Active site; 2) Enzyme-substrate complex; 3) Enzyme-product complex; 4) Enzyme + product. First, the substrate and the enzyme come near to each other, and then the substrate can bind to the active site. The binding of the enzyme to the substrate makes the enzyme-substrate complex. After the substrate is changed to product, but before the product's release, the enzyme is still bound to the product, which is called the enzyme-product complex. Last, the enzyme releases the product from its active site. The enzyme is now ready to accept a new substrate molecule and repeat the same steps.

The concept of the induced fit applies to which part of the enzymatic cycle? Enzyme-Substrate Complex Enzyme-Product Complex Enzyme Substrate Product

Enzyme-Substrate Complex Feedback Correct! Enzyme-Substrate Complex. Recent studies on enzymes have shown that while the substrate and active site are somewhat complementary prior to substrate binding, many enzymes will adjust their active site conformation slightly when the substrate binds, and the Enzyme-Substrate complex is formed, to improve the fit. This is known as induced fit. Think about giving a friend a hug. Your arms are wide open as they come towards you, but only when they are next to you do you close your arms around them. Thus, their proximity causes an "induced fit" with your arms that is a better fit to their body shape than the initial posture of having your arms wide open. Just as you require recognition of your friend prior to embracing them, an enzyme will have some indication from the shape and properties of the molecule, whether it is the correct substrate or not. When the molecule is recognized as the substrate, the enzyme will adjust to form itself around the substrate more tightly to facilitate the reaction is catalyzes.

Some changes to the DNA do not modify the coding sequence of the DNA but do affect its winding and unwinding from nucleosomes. These changes can increase or decrease the availability of DNA and hence, the transcription of a gene. These are called _________ changes? Genetic Epigenetic Epidermal Hypogenetic

Epigenetic Feedback Correct. Epigenetic changes result from modifications of the DNA that affect nucleosome spacing and, therefore, transcription. They do not alter the DNA sequence itself.

Which of the following changes can NOT be detected using PCR? Differences in DNA sequence Epigenetic changes Deletions Insertions

Epigenetic changes Feedback Epigenetic changes do not affect the sequence of the DNA. PCR is used to look at the DNA sequence.

1. The polymerase chain reaction is a tool used to study protein structure. True False

False Feedback PCR is a tool used to amplify a specific segment of DNA.

This amino acid would prefer to interact with oil over water. True False

False Feedback If you selected false, you are correct. The amino acid depicted in this problem is polar/hydrophilic because the end of the amino acid R group has a nitrogen bound to a hydrogen. Other polar amino acids can have oxygen bound to hydrogen, carbons bound to oxygens or carbons bound to nitrogens. Water is also polar, and that is why this amino acid would like to interact with water. And, why the amino acid is categorized as hydrophilic (water loving). Oils are nonpolar and polar amino acids don't like nonpolar molecules.

True or False: Phospholipids that are part of a cell membrane contain only unsaturated fatty acids. False True

False Feedback Correct! Phospholipids may contain various combinations of saturated and/or unsaturated fatty acids.

Both pedigrees show the inheritance of von Willebrand disease, a bleeding disorder in which platelets fail to clot properly. There are different types of von Willebrand disease that exhibit different inheritance patterns. Type I is inherited in an autosomal dominant fashion, while type III is autosomal recessive. Which of the following statements best describes the families depicted in the pedigrees below? Family 1 has type III and Family 2 is unlikely to have either of these two types. Family 1 has type I and Family 2 has type III Both families have type I. Family 1 has type III and Family 2 has type I

Family 1 has type III and Family 2 has type I Feedback Family 1 has carrier parents present and both males and females are affected, so it is type III, autosomal recessive. Family 2 does not have carrier parents and affected males do have unaffected daughters, so it is type I, autosomal dominant.

Which of the following molecules can be used as a precursor for the synthesis of eicosanoids?

Feedback The 20-carbon fatty acid with four double bonds represents arachidonate, the precursor for the eicosanoid cell signalling molecules.

Which of the following best describes the purpose of fermentation? Fermentation enables the production of large amounts of ATP for cells in anaerobic conditions. Fermentation enables the regeneration of NAD+ so that glycolysis can still occur in anaerobic conditions. Fermentation enables the regeneration of NADH so that glycolysis can still occur in anaerobic conditions. Fermentation enables the continued production of acetyl CoA so that glycolysis can still occur in anaerobic conditions.

Fermentation enables the regeneration of NAD+ so that glycolysis can still occur in anaerobic conditions. Feedback Yes! Fermentation regenerates the NAD+ that is essential for glycolysis to occur.

Base excision repair: 1. Fixes single damaged nucleotides 2. Repairs a broken chromosome using genetic information from same chromosome inherited from other parent. 3. Fixes mistakes made by DNA polymerase during DNA replication 4. Fixes multiple damaged nucleotides

Fixes single damaged nucleotides Feedback If you chose, 'Repairs a broken chromosome using genetic information from same chromosome inherited from other parent', that is incorrect. This is the description of a different repair mechanisms, homologous recombination. Homologous recombination occurs to repair a double stranded break in DNA. If you chose, 'Fixes mistakes made by DNA polymerase during DNA replication', this is incorrect. This is the description for DNA Polymerase Proofreading and mismatch repair. This occurs during DNA replication. If you chose, 'Fixes multiple damaged nucleotides', this is incorrect. This is the description for nucleotide excision repair, which occurs to repair DNA damage involving multiple bases. Background. Base excision repair is the repair mechanisms utilized for replaced a single damaged nucleotide

What happens to glucose under anaerobic conditions? Glucose is converted into acetyl-CoA. Glucose levels increase while the cells wait for oxygen supplies to increase so aerobic metabolism can occur. Glucose proceeds to the citric acid cycle. Glucose undergoes glycolysis to produce pyruvate.

Glucose undergoes glycolysis to produce pyruvate. Feedback Yes, glucose is converted to pyruvate.

Which molecules undergo anaerobic metabolism? Fatty acids and glucose Glucose, some fatty acids, and glycerol Glucose, some amino acids, and glycerol acetyl-CoA and all fatty acids

Glucose, some amino acids, and glycerol Feedback Yes! Any molecule that can enter glycolysis can be used in anaerobic metabolism.

Lipases are enzymes that break down triglycerides into ________ and three free fatty acids. Sterols Glucose Glycerol Vitamins

Glycerol Feedback Correct! Glycerol is part of a triglyceride. Sterols, glucose, and vitamins are not constituents of a triglyceride molecule.

Hemoglobin acts as a buffer and controls the pH of the blood by binding __________. oxygen bicarbonate ion H+ ions carbon dioxide

H+ ions Feedback Correct! Hemoglobin can regulate pH by binding to H+.

Hemoglobin acts as a buffer and controls the pH of the blood by binding to __________. oxygen bicarbonate ion H+ ions carbon dioxide

H+ ions Feedback Correct! pH is a function of the concentration of H+ (low pH, high H+ and vice versa), so hemoglobin binding to H+ will lower the H+ concentration and raise the pH (less acidic), while hemoglobin releasing H+ will increase the H+ concentration and lower the pH (more acidic).

A patient with advanced cancer has not been able to eat a full meals for the past three months, and his intake has gradually diminished over the last month such that his entire intake in the prior three days consists solely of water. Which of the following is most likely? Glycogen is his major source for producing ATP Fatty acid synthesis is favored over beta oxidation of fatty acids He is likely to have lost adipose tissue and muscle mass His blood sugar level will be very high

He is likely to have lost adipose tissue and muscle mass Feedback Correct! He is likely to have lost adipose tissue and muscle mass. Under long term starvation like conditions, the body would have already utilized any stored form of glycogen to produce glucose, in return ATP to meet the energy needs. Thus, the adipose tissue, and proteins from the muscle are catabolized to provide energy under such conditions.

Billy is a 26-year-old male currently on his 12th day of a hunger strike to protest "government stuff." How can Billy keep going long after his glycogen supply has been used up? (Note: The brain requires a constant supply of glucose to function.) He uses fatty acids to create new glucose through gluconeogenesis. He uses glycerol, some amino acids, and other molecules to create new glucose. All amino acids can be used to create glucose through gluconeogenesis.

He uses glycerol, some amino acids, and other molecules to create new glucose. Feedback Correct!He uses glycerol, some amino acids, and other molecules to create new glucose. The glycerol part of triglycerides (more on this in the next module on lipids), lactate (recall the Cori cycle), and certain amino acids can be converted in the liver to glucose. The process by which glucose is formed from these noncarbohydrate sources is called gluconeogenesis (gluco = glucose, neo = new, genesis = make). About 60% of the amino acids in the body can be used for gluconeogenesis. Lactate and amino acids such as alanine and serine are converted to pyruvate, which then may be synthesized into glucose or enter the citric acid cycle. Glycerol may be converted into glyceraldehyde 3-phosphate, which may continue on in glycolysis to make pyruvate or be used to synthesize glucose via gluconeogenesis.

Which of the following statements accurately describes cooperativity? Myoglobin can bind subsequent molecules of oxygen more easily after the first oxygen molecule binds. Myoglobin and hemoglobin work together to deliver oxygen to the tissues. Hemoglobin can bind subsequent molecules of oxygen more easily after the first oxygen molecule binds. Oxygen and carbon dioxide exchange occurs in the alveoli of the lungs.

Hemoglobin can bind subsequent molecules of oxygen more easily after the first oxygen molecule binds. Feedback Correct! Hemoglobin has four subunits (polypeptide chains) and can bind up to four oxygen molecules. As each oxygen binds hemoglobin, the affinity of hemoglobin for oxygen increases. Increased affinity is caused by a conformational change, or a structural change in hemoglobin. Because myoglobin has only one subuint (one polypeptide chain), myoglobin cannot exhibit cooperativity.

Hemoglobin transports oxygen and myoglobin stores oxygen. They exhibit different oxygen binding curves when plotted on a graph with total partial pressure of the oxygen (x-axis) plotted against the percent saturation of hemoglobin (y-axis). What is the shape of the oxygen binding curves for hemoglobin and myoglobin? Hemoglobin has a sigmoidal curve, whereas myoglobin has a hyperbolic curve Myoglobin has a sigmoidal curve, whereas hemoglobin has a hyperbolic curve Both have a sigmoidal curve Both have a hyperbolic curve

Hemoglobin has a sigmoidal curve, whereas myoglobin has a hyperbolic curve Feedback Correct! Since hemoglobin binds oxygen in a cooperative manner, it has a sigmoidal curve, whereas myoglobin only binds one molecule of oxygen, so it has a hyperbolic curve.

Does oxygenated hemoglobin have a high or low affinity for carbon monoxide (CO)? High affinity for CO Low affinity for CO

High affinity for CO Feedback Correct! Carbon monoxide (CO), which is similar in shape to oxygen (O2), binds to the iron (Fe) atom in the heme group when hemoglobin is in the R state and the heme group is planar, just like oxygen does. Hemoglobin binds to carbon monoxide with 200 times the affinity of oxygen, which means it is very difficult to get rid of the carbon monoxide once it is bound to hemoglobin.

Proteins that promote coiling of DNA and help prevent DNA strands from "tangling" are called? Histones Enzymes Polymerase Chaperones

Histones Feedback Correct! The combination of DNA and histone proteins creates nucleosomes.

A diabetic patient is suffering from ketoacidosis. Which interaction(s) could be disrupted within the patientʼs hemoglobin due to this condition. (Click all that apply) Hydrogen Bond Disulfide Bond Hydrophobic Interactions Ionic Bonds

Hydrogen Bond Ionic Bonds Feedback Correct! Diabetic ketoacidosis leads to a lower pH than normal. Changes in pH can disrupt both hydrogen bonds and ionic bonds inside of a protein.

Saturated fatty acids have more _________________ than unsaturated fatty acids of the same length. Carbon atoms Oxygen atoms Hydrogen atoms double bonds

Hydrogen atoms Feedback Correct! Saturated fatty acids contain more hydrogen atoms than unsaturated fatty acids. Saturated fatty acids do not have double bonds between the carbons within the hydrocarbon chain. Fatty acids have the same amount of oxygen atoms, two. These oxygen atoms are found within the carboxylate group. Both saturated and unsaturated fatty acids can have up to 24 carbons.

What bonds can the R group of this amino acid form to stabilize tertiary structure? Hydrogen bonds and ionic bonds Ionic bonds and disulfide bonds Hydrogen bonds and disulfide bonds

Hydrogen bonds and disulfide bonds. Feedback Correct! Charged amino acids have R groups with visible positive or negative charges and form ionic bonds. Polar amino acids have R groups with S-H, N-H, O-H, C-N, or C=O bonds and can form hydrogen bonds. Cysteine can also form a disulfide bond with its terminal S-H. Non-polar amino acids have R groups with C-H bonds and hide from water on the inside (or core) of proteins

3. Which type of bonding or interaction is correctly paired with a chemical or change in environment that will disrupt/break the interaction or bond? Peptide bonds: Reducing agents Hydrophobic interactions: Change in pH Peptide bonds: Change in pH Hydrogen bonds/ionic bonds: Change in pH

Hydrogen bonds/ionic bonds: Change in pH Feedback Correct! Hydrogen bonds and ionic bonds can be disrupted by changes in pH. High salt concentrations can also disrupt ionic bonds / hydrogen bonds, heat disrupts hydrophobic interactions, and reducing agents disrupt sulfide bonds.

What type of reaction breaks peptide bonds apart? Condensation Reaction Methylation Reaction Hydrolysis Reaction Oxidation/Reduction Reaction

Hydrolysis Reaction Feedback Correct! Peptide bonds are formed by dehydration reactions (named for the loss of water that occurs) and broken via hydrolysis (named for the addition of water: "hydro-" meaning water, and "-lysis" meaning cutting, i.e. water cuts the peptide bond).

Alzheimer disease is caused by aggregation of the Amyloid beta peptide and tangle formation by the tau protein. What kinds of amino acids are likely to drive the formation of these protein aggregates? Hydrophobic Hydrophilic Polar Cysteine

Hydrophobic Feedback Correct! The Amyloid beta plaque and tau protein become misfolded, exposing hydrophobic amino acids on their exterior. When hydrophobic amino acids are exposed to water, they actively seek out ways to avoid that water. One way to do this is to find other exposed hydrophobic amino acids, located on other misfolded proteins. When misfolded proteins begin to gather, they form aggregates, ultimately resulting in neuronal cell death.

A patient presents with a fever of 110°F. Which interaction(s) would be disrupted within a neuronal protein if the fever is not resolved quickly. Hydrogen Bond Disulfide Bond Hydrophobic Interactions Ionic Bonds

Hydrophobic Interactions Feedback Correct! The patient's temperature is much higher than normal. High temperatures disrupt hydrophobic interactions.

As a piece of bacon is heated in a skillet on the stove, you observe that the appearance of the bacon changes. You may even notice that the bacon becomes crispy if left in the skillet. What types of bonds or interactions in proteins are susceptible to temperature changes? Ionic Bonds Hydrogen Bonds Hydrophobic interactions Disulfide Bonds

Hydrophobic interactions Feedback Correct! Just as protein structure is stabilized primarily by the hydrophobic effect, disruption of the hydrophobic effect and hydrophobic interactions is the simplest way to denature a protein. This is generally done by applying heat. High temperatures cause the atoms in a protein to move so quickly that the structure loosens and causes the hydrophobic core to open up and expose the nonpolar residues to water.

During the reactions of the Electron Transport Chain, hydrogens are pumped by complexes __________ and move from the matrix to the _________. I, II, & III; intermembrane space I, III, & IV; cytoplasm I, III, & IV; intermembrane space II & IV; cytoplasm

I, III, & IV; intermembrane space Feedback Correct! During the reactions of the Electron Transport Chain, hydrogens are pumped by complexes I, III, & IV and move from the matrix to the intermembrane space.

In which of the following patients is the planar conformation of the heme group in hemoglobin favored? In a girl with diabetic ketoacidosis In a firefighter who is brought to the emergency room after entering a burning building In an older woman with pneumonia and sepsis who has a blood pH of 7.1 In the muscle capillaries of a patient who is on a treadmill for a cardiac stress test

In a firefighter who is brought to the emergency room after entering a burning building Feedback Correct! The planar conformation of heme would be favored under conditions of high pH (at high pH, hemoglobin prefers to bind oxygen and heme is in the planar conformation). A hospitalized firefighter would presumably be receiving oxygen and would thus have more hemoglobin in the oxygen binding conformation.

Which one of the following paths requires less activation energy to convert the reactants into the products? The options include the path indicated by a bold line, and the path indicated by a dotted line. In presence of an enzyme-Dotted line In absence of an enzyme-Bold line

In presence of an enzyme-Dotted line Feedback Correct! The dotted line represents the path with the lower activation energy, or the one in which less activation energy is required to get the reaction started. The reactants have a lower energy hill to climb to begin the reaction.

Increases Feedback Correct! Increases. When hexokinase is inhibited, it can no longer convert the substrate, glucose, into the product, glucose-6-phosphate. Glucose therefore accumulates when hexokinase is inhibited.

In the reaction provided below, glucose-6-phosphate accumulates in the cell and binds to hexokinase at a site that is distinct from the active site. This prevents hexokinase from binding to its substrate. What happens to the amount of glucose in the cell once hexokinase is inhibited? Stays the same Increases Decreases

Non-competitive inhibition Feedback Correct! Non-competitive. Glucose-6-phosphate binds to a site different than the active site, indicating that it is binding an allosteric site. When an allosteric site is bound by an inhibitor, the active site is altered, preventing substrate binding. This is the definition of non-competitive inhibition.

In the reaction provided below, glucose-6-phosphate accumulates in the cell and binds to hexokinase at a site that is distinct from the active site. This prevents hexokinase from binding to its substrate. What type of inhibition is occurring in this example? Competitive inhibition Non-competitive inhibition anti-competitive inhibition

A black female mouse mates with a white male mouse and produces a litter of all gray mice. Which inheritance pattern can be used to describe this situation? Complete Dominance Recessive Incomplete Dominance Codominance

Incomplete Dominance Feedback Incomplete dominance produces a blended phenotype.

If the coding (non-template) DNA sequence of a normal gene is 5' GTC GCA TGG TGA 3', what kind of mutation would create the mutant gene sequence 5' GTC GAC ATG GTG A 3'? Deletion mutation Silent mutation Insertion mutation Nonsense mutation

Insertion mutation Feedback Correct! Nucleotides were inserted into the original sequence Background. An insertion mutation inserted an A in the second position of the second codon (GCA). Notice that there are now more nucleotides in the mutant gene compared to the normal gene.

What effects does insulin have on metabolism?

Insulin has several effects on metabolism. It stimulates uptake of glucose into the cell. It also increases protein synthesis, glycogen synthesis and fatty acid synthesis and storage.

Hemoglobin and myoglobin proteins bind molecular oxygen. The protein subunit of hemoglobin does not bind directly to the oxygen. Instead, a specific atom binds oxygen. In hemoglobin, which of the following will directly bind oxygen? Histidine Heme Carbon Monoxide Iron

Iron Feedback Correct! Hemoglobin contains a heme group, which contains an iron atom. Oxygen binds directly to the iron atom in the heme group.

Lipoproteins are specialized proteins that are made of a lipid+protein. Certain lipoproteins have cholesterol as the lipid component. What form of cholesterol lipoproteins are found in the bloodstream? LDL MDL LSD LLD

LDL Feedback Correct! In the bloodstream, cholesterol is found in LDL, low-density lipoproteins.

Under anaerobic conditions in humans, which molecule is formed in the cytosol by fermentation? Lactate Fructose Glucose-6-phosphate Acetyl-CoA

Lactate Feedback Correct! Lactate is formed from pyruvate under anaerobic conditions.

If the fatty acid in the red box is replaced with the following fatty acid: CH3(CH2)18COOH, what will be a likely result? Membrane fluidity will remain the same Membrane fluidity will be increased Membrane fluidity will decrease

Membrane fluidity will decrease Feedback Correct! Replacing an unsaturated fatty acid tail with a saturated fatty acid tail within a phospholipid molecule will result in decreased fluidity because saturated fatty acids stack better together and make the molecule more stable. Which means a more solid state is favored, not a liquid (fluid) state.

The following is the mRNA sequence for actin, a protein that provides structure to a cell: 5' ACU AGA CGU UUU UAA 3'. A mutation to the actin gene results in the production of the following mRNA: 5' ACU AGA CAU UUU UAA 3' What type of mutation is this? Silent Missense Nonsense Frameshift

Missense Feedback If you chose, Nonsense mutation, this is incorrect. A nonsense mutation is a point mutation that results in a change to a stop codon, the change here is to a different amino acid (His). If you chose, Silent mutation, this is incorrect. A silent mutation changes the codon, however, it doesn't change the resulting amino acid encoded. If you chose, frameshift mutation, this is incorrect. Frameshift mutations are not point mutations and are usually the result of an insertion or deletion. As such, inserting or deleting nucleotides will change the number of nucleotides present causing a shift in the reading frame. For example, if we read the sentences CAT HAT DOG and deleted the 'A' in CAT we would change the reading frame to CTH ATD OG. Background: CGU in the normal gene is mutated to CAU, changing the amino acid from arginine (Arg) to histidine (His). A change in a codon that also changes one amino acid in the protein is a missense mutation.

Myoglobin stores oxygen, whereas hemoglobin transports oxygen. Which of the following statements accurately describes the affinity of myoglobin and hemoglobin for oxygen? Hemoglobin and myoglobin both have the same affinity for oxygen. Hemoglobin has a higher affinity for oxygen compared to myoglobin. Myoglobin has exactly one-quarter of the affinity for oxygen because it has only one subunit. Myoglobin has a higher affinity for oxygen compared to hemoglobin.

Myoglobin has a higher affinity for oxygen compared to hemoglobin. Feedback Correct! Since myoglobin stores oxygen, it has a higher affinity for oxygen.

The citric acid cycle produces what?

NADH and FADH2

A type II diabetes patient who has been on metformin treatment along with making some life style changes for over two months now has a current A1C level reading of 7% . Which of the following statements best describes his response to the treatment and management of the condition? No, the patient is not responding to the treatment since the normal range of A1C levels in healthy individuals is 0-5% Yes, he is responding to the treatment well since the normal range of A1C levels in healthy individuals is 0-10%

No, the patient is not responding to the treatment since the normal range of A1C levels in healthy individuals is 0-5% Feedback Correct! The normal range of A1C levels in healthy individuals is anywhere from 0-5%. A level above 6.5% indicates a high Glucose concentration. Since the patient's A1C levels are at 7%, it is clearly indicating that his/her blood sugars levels are not in the normal range and the patient is not responding well to the treatment. A diagnosis of diabetes is usually made when the levels of A1C are above 6.5%. A1C is a good indicator of how well the diabetes is being managed on a consistent basis since it is an average of glucose levels over a time range of 120 days (the average lifespan of an RBC) rather than simply the levels for that day.

When an inhibitor binds reversibly to a site of the enzyme that is not the active site, what type of inhibition results? Anti-competitive Non-competitive Mixed None of the options

Non-competitive Feedback Correct! The correct answer is 'Non-competitive.' Enzymes can be inhibited by substances called non-competitive inhibitors. Some non-competitive inhibitors attach to the enzyme at an allosteric site, which is a site other than the active site. The presence of the non-competitive inhibitor changes the shape of the enzyme enough to interfere with binding of the normal substrate. Some non-competitive inhibitors are used in the regulation of metabolic pathways, but others are poisons. Such inhibitors distort the tertiary protein structure and alter the shape of the active site. Any enzyme molecule thus affected can no longer bind it's substrate, so the enzyme cannot catalyze a reaction. Although some non-competitive inhibitors bind reversibly, others bind irreversibly and permanently inactivate the enzyme molecules, thereby greatly decreasing the reaction rate. In non-competitive inhibition, increasing the substrate concentration does not increase the reaction rate as it does in the presence of a competitive inhibitor.

Which characteristic correctly describes the amino acid shown below? Charged Polar Non-polar

Non-polar Feedback Correct! Side chains that are predominantly carbon and hydrogen are nonpolar.

Several components of cigarette smoke, including benzopyrene, insert themselves (intercalate) into the DNA and lead to several types of mutations such as frameshift mutations, including both insertions and deletion. Which of the following repair pathways would be used to repair this type of damage? Base excision repair Mismatch Repair Nucleotide Excision Repair Homologous Recombination

Nucleotide Excision Repair Feedback Correct! Nucleotide excision repair is used to repair deletions, insertions, and helix-distorting lesions, such as thymine dimers.

13. Myoglobin and hemoglobin each have different numbers of subunits and this affects their respective oxygen storage and delivery capabilities. How many subunits does myoglobin have versus hemoglobin? One, Four Two, Three One, Two Four, One

One, Four Feedback Correct! Myoglobin has one subunit and hemoglobin has four subunits.

Antibodies that enable our body to fight bacterial infections must bind to antigens on the surface of the bacterial cell. If the antigen on the surface of the bacterial cell has several negatively charged amino acids, which of the following amino acids would you expect to find on the portion of the antibody that binds to the antigen? Option 1 Option 2 Option 3 Option 4

Option 1 Feedback If you selected option 1, you are correct. Positive charged amino acids will be attracted to the negatively charged amino acids.

A missense mutation resulting in a change from asparagine to leucine at a specific position on an enzyme leads to a neurodegenerative disease. Is there an alternate amino acid substitution of a missense mutation listed below that would have less of an impact on the protein structure and consequently its function than the proposed leucine substitution would? Option 1 Option 2 Option 3 Option 4

Option 2 Feedback Correct! Glutamine is a polar amino acid and so is asparagine,. They are polar because they contain C-N, C-O, O-H or N-H bonds on the outside surface of their R groups. A replacement of one category of amino acid for another in the same category has the best chance of being tolerated and not affecting the protein.

Craniofrontonasal Dysplasia is an X-linked Dominant disorder. This condition is very rare and is caused by mutations in the Ephrin B-1 gene. Which one of the following pedigrees portrays the familial inheritance pattern of this X-linked Dominant disorder? Option 1 Option 2 Option 3 Option 4

Option 4 Feedback To first differentiate between dominant and recessive, check to see if any carriers are present in any generation. Options 1 and 3 are Recessive inheritance patterns because they both contain the pattern where two parents are unaffected and have a child that is affected. Option 1 is X-linked Recessive because only males are affected in the entire pedigree. Option 3 is Autosomal Recessive because there is an affected female. Since Options 2 and 4 are both Dominant, we look to see which one has a pattern where an affected father has daughters that are all affected. Option 2 has an affected father with an affected son, so this must be Autosomal Dominant. Option 4 demonstrates an affected father passing the disease down to all of his daughters, so the answer is Option 4.

Cyanide binds to complex IV of the electron transport chain, preventing electron transport. Which of the following would be the most immediate effect(s) of cyanide consumption? (Select all that apply) Oxygen would not be consumed by the ETC. ATP will build up. ADP will build up. ATP synthase will produce ATP. Protons will not be pumped to the intermembrane space.

Oxygen would not be consumed by the ETC. ADP will build up. Protons will not be pumped to the intermembrane space. Feedback Correct! If cyanide was bound to complex IV, then oxygen would not be consumed by the ETC, ADP will build up and Protons will not be pumped to the intermembrane space.

1. Gleevec is a competitive inhibitor and prevents ATP from binding with the active site of the enzyme. Competitive inhibitors bind to an enzyme in the active site. Gleevec is binding in the same site as ATP. ATP is the substrate, to the site of ATP binding must be the active site. Gleevec is therefore is binding the active site and is a competitive inhibitor. If you chose, "Gleevac is a non-competitive inhibitor..." this is incorrect because non-competitive inhibitors bind at a site different than the active site. In the figure it can be seen that Gleevac binds the same site on the enzyme as the substrate (ATP). This means that Gleevac is binding the active site. If you chose "Gleevac is a competitive inhibitor that binds to an allosteric site...", this is incorrect because competitive inhibitors bind the active site, not an allosteric site.

Patients with chronic mylogenous leukemia (CML) have a mutation that results in the production of BCR-ABL, an enzyme that speeds up cell division using ATP as a substrate. The drug Gleevec impairs the activity of the enzyme. Using the illustrations of the enzyme above, what best describes how the drug exerts its effect? 1. Gleevec is a competitive inhibitor and prevents ATP from binding with the active site of the enzyme. 2. Gleevec is a competitive inhibitor that binds to an allosteric site on the enzyme to prevent ATP from binding to the active site. 3. Gleevec is a non competitive inhibitor and prevents ATP from binding with the active site of an enzyme. 4. Gleevec is a non competitive inhibitor that binds to an allosteric site on the enzyme to prevent ATP from binding to the active site.

2. Increase activity of phenylalanine hydroxylase. Feedback Correct! Increase activity of phenylalanine hydroxylase. Increased phenylalanine levels lead to phenylketonuria, so symptoms can be relieved by decreasing the level of phenylalanine. By increasing the activity of the enzyme that uses phenylalanine, phenylalanine hydroxylase, we can decrease the phenylalanine levels.

Phenylalanine is toxic to the developing brain. Using the following schematic, propose a suggestion to alleviate the problems associated with Phenylketonuria. 1. Supplement phenylalanine in the diet. 2. Increase activity of phenylalanine hydroxylase. 3. Decrease activity of phenylalanine hydroxylase. 4. Supplement tyrosine in the diet.

Phenylalanine hydroxylase is an enzyme that breaks down phenylalanine in the body. When there are low levels of this enzyme, as seen in Phenylketonuria, what is the consequence? Phenylalanine levels increase. Phenylalanine levels decrease. Tyrosine levels increase.

Phenylalanine levels increase. Correct! Phenylalanine levels increase. Phenylalanine is the substrate of the enzyme phenylalanine hydroxylase. If the level of this enzyme is low, then the level of its substrate, phenylalanine, will increase.

Which of the following components would you find in a cellular (fluid mosaic) plasma membrane?

Phospholipids Feedback Correct! Phospholipids are major components of the cell membrane.

During periods of strenuous exercise, the muscle cells can become anaerobic. Without oxygen, the electron transport chain cannot continue and the citric acid cycle slows down. When this occurs, how do cells make ATP? Pyruvate remains untransformed. Pyruvate produces acetyl Co-A and enters the citric acid cycle. Pyruvate is transformed to lactate. There is no requirement for ATP in the muscles.

Pyruvate is transformed to lactate. Feedback Correct! Part of the process of making ATP anaerobically is to convert pyruvate to lactate.

Which of the following components is NOT used in PCR? DNA template DNA nucleotides RNA polymerase Primers

RNA polymerase Feedback PCR makes a DNA copy, so DNA polymerase is used.

What color is the primer in the following diagram? Red Purple Blue

Red Feedback Recall from the section on DNA replication that DNA polymerase needs a primer to begin DNA synthesis. This requirement means the primers will direct the DNA polymerase to only synthesize complementary strands of the target DNA. (Note: In DNA replication, the primers are RNA primers, while PCR generally uses DNA primers because they are more stable.)

Why is the Cori Cycle important for red blood cells? Red blood cells have no mitochondria. In red blood cells, the Cori Cycle prepares acetyl-CoA for the citric acid cycle. The Cori Cycle helps regulate how tightly oxygen is bound to hemoglobin in red blood cells. The Cori Cycle is the only way that red blood cells can create NADH and FADH2.

Red blood cells have no mitochondria. Feedback Correct! Red blood cells contain no mitochondria and therefore rely on anaerobic metabolism for ATP.

Alkaline phosphatase is produced by bone and liver in the human body. The amount of alkaline phosphatase in blood can help identify if a patient potentially has certain types of bone and/or liver-related disease, including Paget disease, hepatitis, and certain types of cancer. The optimal pH range for alkaline phosphatase activity is a pH of 8.0 to 10.0. What happens to the activity of the alkaline phosphatase at a pH of 2.0? Slightly decreases Slightly increases Significantly increases Significantly decreases

Significantly decreases Feedback Correct! Significantly decreases. This particular enzyme's optimal pH, the pH where it will have the highest activity, is between 8.0 and 10.0. Putting it into a notably different pH, like 2.0, will significantly decrease the activity.

Glycolysis produces two ATP molecules. Through what process are these ATP molecules made? Beta oxidation Electron transport chain Oxidative phosphorylation Substrate level phosphorylation

Substrate level phosphorylation Feedback If you chose "Beta Oxidation" that is incorrect. Beta oxidation is the pathway that is used to metabolize fatty acids. Substrate-level phosphorylation is the only way ATP can be made without oxygen. If you chose "Electron Transport Chain" that is incorrect. The electron transport chain facilitates in the aerobic production of ATP. Substrate-level phosphorylation is the only way ATP can be made without oxygen. If you chose "Oxidative phosphorylation" that is incorrect. Oxidative phosphorylation is the process in which ATP is made aerobically. Substrate-level phosphorylation is the only way ATP can be made without oxygen. The correct answer is "Substrate level phosphorylation"

Glycolysis produces two ATP molecules through which process? Oxidative phosphorylation Beta oxidation Electron transport chain Substrate level phosphorylation

Substrate level phosphorylation Feedback Correct! Substrate level phosphorylation transfers a phosphate group from an intermediate of glycolysis directly to ADP creating ATP.

Which level of protein structure provides enzymes with their substrate specificity? Primary structure Secondary structure Tertiary structure

Tertiary structure Feedback Correct! The tertiary structure of the enzyme is the level that places the right amino acids into the right locations so that the enzyme can act like a baseball glove and wrap itself around the correct substrate. A baseball glove is designed to catch baseballs, not other types of balls, so it is specific for baseballs. In this way, the enzyme is designed to "catch" one type of substrate, based on the locations of the R groups of the amino acids in 3D space (tertiary structure), when it wraps up just the right way around the substrate in the active site.

In the absence of oxygen in the exercising muscle, why does the amount of lactate in the blood change? When oxygen is not present, muscles use lactate to make ATP through the glycolysis pathway.. Lactate decreases since it is produced by metabolizing muscle but has no other use in the body. The amount of lactate increases because lactate produced in muscles anaerobically must travel to the liver. The amount of lactate does not change in the absence of oxygen in exercising muscles.

The amount of lactate increases because lactate produced in muscles anaerobically must travel to the liver. Feedback Correct! Lactate produced during anaerobic metabolism leaves the muscle cells and travels to the liver via the blood.

2. Non-competitive inhibition of acetylcholinesterase. Feedback Correct! Non-competitive inhibition of acetylcholinesterase. If acetylcholinesterase is inhibited, then the substrate, acetylcholinesterase, will increase. If the inhibitor is a competitive inhibitor, the substrate levels will eventually overcome the inhibition, which will be relieved. If the inhibitor is a non-competitive inhibitor, the concentration of substrate does not affect the inhibition. Therefore, non-competitive inhibition of acetylcholinesterase is the best approach.

The enzyme acetylcholinesterase breaks down acetylcholine in the brain leading to neuron degeneration. Which of the following strategies represents the best way to increase acetylcholine levels? 1. Allosteric activation of acetylcholinesterase. 2. Non-competitive inhibition of acetylcholinesterase. 3. Increase gene expression for acetylcholinesterase. 4. Competitive inhibition of acetylcholinesterase.

What happens to the enzyme at the end of the cycle? The enzyme shape is altered and it cannot be re-used for another reaction. The enzyme is used again. The enzyme will bind to a substrate. Remains bound to the product. The enzyme is destroyed.

The enzyme is used again. The enzyme will bind to a substrate. Feedback Correct! During the process of changing the substrate into product and product release, the amino acids in the active site where the chemistry occurred on the substrate are changed back into their original state. This means that, when the product is formed and then released, the same amino acids will then be available to accept the next substrate molecule and repeat the same chemistry. A catalyst, in general, is a substance that speeds up a reaction by lowering the activation energy for the reaction. It is also unchanged, overall, from the form it was in at the start of the reaction. This means that it can be used over and over again. Enzymes are special protein catalysts that accept specific substrates and turn them into products, and are used in an incredible number of chemical reactions in living organisms.

2 ATP are generated when glucose is broken down in the muscle cell and 6 ATP are consumed when glucose is regenerated in the liver. Feedback 2 ATP are generated when glucose is broken down in the muscle cell (through glycolysis) and 6 ATP are consumed when ATP is regenerated in the liver (through gluconeogenesis.

The figure of the Cori Cycle below demonstrates how glucose is consumed in the muscle cell and regenerated in the liver. How many ATP are produced in the muscle cell when glucose is broken down and how many ATP are consumed in the liver when glucose is regenerated? 2 ATP are generated when glucose is broken down in the muscle cell and 6 ATP are consumed when glucose is regenerated in the liver. 2 ATP are generated when glucose is broken down in the muscle cell and 4 ATP are consumed when glucose is regenerated in the liver. 6 ATP are generated when glucose is broken down in the muscle cell and 2 ATP are consumed when glucose is regenerated in the liver. 30 ATP are generated when glucose is broken down in the muscle cell and 6 ATP are consumed when glucose is regenerated in the liver.

If lysine is required at position #150 in the peptide chain in order for a protein to properly fold and function, what happens if amino acid #150 is mutated from lysine to alanine? The protein will fold properly-no change The protein will not fold properly

The protein will not fold properly Feedback Correct! Changing lysine (positively charged amino acid, forms ionic bonds, is hydrophilic) to alanine (a non-polar amino acid, does not form ionic bonds, is hydrophobic) eliminates one or more important interactions and will prevent the protein from properly folding.

Which of the following differentiates aerobic from anaerobic cellular metabolism? The utilization of O2 as an electron acceptor The production of ATP The breakdown of glucose into compound with fewer carbon atoms The use of ingested food to create energy

The utilization of O2 as an electron acceptor Feedback Yes! Only aerobic metabolism depends on oxygen as the terminal electron acceptor in the electron transport chain.

Which of the following are characteristics of enzymes? (select all that apply) They are reusable They increase activation energy They speed up a reaction They catalyze a specific type of reaction

They are reusable They speed up a reaction They catalyze a specific type of reaction Feedback Correct! Enzymes are called catalysts, which means they help speed up a reaction, and they are not used up by the reaction. They are also specific, which means they catalyze a specific type of reaction or use a particular type of substrate. They have the right amino acids in the right places to help change the substrate into product, and they still have these amino acids when the reaction is over.

What do NADH and FADH2 carry?

They carry high energy electrons to the electron transport chain, which fuels the production of ATP.

Which compound makes up the greatest reserves of energy in our bodies? Glycogen Triglycerides Cholesterol Fatty acids

Triglycerides Feedback Correct! The greatest reserves of energy in our bodies are stored as triglycerides. Triglycerides consist of one glycerol molecule and three fatty acids. When triglycerides are broken down, the glycerol can enter glycolysis while the fatty acids enter beta oxidation.

DNA polymerase is used in DNA replication and in PCR. True False

True Feedback Both PCR and DNA replication require DNA polymerase to make new copies of DNA.

Anabolic pathways result in larger molecules being made from smaller molecules and Catabolic pathways result in larger molecules being broken down into smaller molecules. True False

True Feedback Correct! Anabolism creates larger molecules from smaller molecules and Catabolism breaks down larger molecules into smaller molecules.

Select True or False: the lower the activation energy for a reaction, the faster the reaction rate. True False

True Feedback Correct! If less energy is needed to get the reaction over the energy hill, it goes faster. Enzymes help bring all of the items needed for a reaction together in the best way, so less energy is needed for the reaction to get started. This lowers the activation energy for the reaction and speeds up the reaction so that it can go much faster than if the enzyme were not present.

A thermocycler is a machine used for PCR that varies the temperature of a sample. True False

True Feedback For PCR, in each cycle, the two strands of the duplex DNA are separated by heating, then the reaction mixture is cooled to allow the primers to anneal (or pair) to their complementary segments on the DNA. Next, the DNA polymerase directs the synthesis of the complementary strands. The use of a heat-stable DNA polymerase eliminates the need to add fresh enzyme after each round of heating (heat inactivates most enzymes). Hence, in the presence of sufficient quantities of primers and dNTPs, PCR is carried out simply by cycling through the different temperatures for strand separation, primer annealing, and DNA synthesis. The thermocycler is the machine that is used to vary the temperature of the samples.

This amino acid is polar. True False

True Feedback If you selected true, you are correct. The amino acid depicted in this problem is polar/hydrophylic because the end of the amino acid R group has an oxygen bound to a hydrogen. Other polar amino acids can have nitrogen bound to hydrogen, carbons bound to oxygens or carbons bound to nitrogens.

dNTPs are DNA nucleotides used in PCR. True False

True Feedback dNTPs stands for deoxynucleotide triphosphates, which are the nucleotides used in DNA synthesis.

Glucose that is phosphorylated after entering the cell cannot move through GluT transporters. True False

True Feedback Correct! Glucose that is phosphorylated after entering the cell cannot move through GluT transporters.

Which of the following are possible effect(s) that phosphorylation/dephosphorylation can have on the activity of an enzyme? Select all that apply. Turn the enzyme "on". Increase the amount of substrate for the enzyme. Turn the enzyme "off". Alter the amino acid sequence of the enzyme

Turn the enzyme "on". Turn the enzyme "off". Feedback Correct! Phosphate groups are added/removed by phosphorylation/dephosphorylation. Adding or removing a phosphate group is like 'flipping a switch' on the enzyme's activity. It is a way of modulating or regulating, enzyme activity. The correct answers are both 'Turn the enzyme on' and 'Turn the enzyme off.'

here are two types of diabetes mellitus (DM) that lead to impairment in glucose utilization. Resistance to the effects of insulin leads to which type of DM? Type I diabetes Type II diabetes Both types of diabetes

Type II diabetes Feedback If you answered- Type I diabetes - the answer is not correct. Type I DM is due to an inability of the the pancreas to produce insulin and is not due to resistance to the effects of insulin. If you answered- Both types of diabetes - the answer is not correct. Type I diabetes is a result of decreased ability to produce the hormone insulin. Whereas, in the type II diabetes, the cells can produce insulin but the cells are resistant to the effects of insulin. Diabetes results from a decreased ability to produce insulin or a decreased sensitivity of cells to the insulin produced by the body (type I and type II, respectively). This leads to excessively high blood glucose levels that are damaging to various organs and systems in the body.

Essential fatty acids are unsaturated fatty acids and have an omega 3 and/or and omega 6 double bond.

Which of the following is an essential fatty acid?

A woman is homozygous for an abnormal allele on Chromosome 2 that codes for an autosomal dominant disease. This means that she: Will have the disease Will not have the disease Has one normal gene and one abnormal gene Can pass on two genes to any daughters and one gene to any son

Will have the disease Feedback Homozygous means that the woman will have two copies of the abnormal allele. An abnormal allele is the allele that can lead to disease. Since the disease is dominant, then the abnormal allele is dominant in this case. With two copies of a dominant allele, an individual will inherit a dominant disease.

Which of the following would be considered a point mutation to a DNA strand that consists of a nucleotide sequence: 5' CTG ACG TAT CTT AAT 3' a. 5' CTG ACG TAA CTT AAT 3' b. 5' CTG ACG TAT TTA AT 3' c. 5' CTG ACG TAT TCT TAA T 3' d. 5' CTG ACG TAT CTT AAT 3'

a. 5' CTG ACG TAA CTT AAT 3' Feedback Correct! A point mutation changes a single nucleotide in a codon, in this case, changing the T in the third position of the third codon to an a (TAT > TAA).

If the coding (non-template) DNA sequence of a normal gene is 5' GTC GCA TGG TGA 3', which DNA sequence would represent a nonsense mutation? q. 5' GTC GCA TAG TGA 3' b. 5' ATC GCA TGG TGA 3' c. 5' GTC GCA TGT GA 3' d. 5' GTA GCG TGG TGA 3'

a. 5' GTC GCA TAG TGA 3' Feedback If you chose, 5' GTC GCA TGT GA 3', this is incorrect because the change here (TGG in the third codon to TGT) results from the loss of a single base (G) at the end of the third codon. Then, the first T from the 4th codon becomes the third base of the third codon, 'shifting' the reading frame. This is a deletion mutation in the DNA. If you chose, 5' GTA GCG TGG TGA 3', this is incorrect because the change here (GTC to GTA in the first codon) would change one Val codon to another Val codon. This is a point mutation in the DNA that would result in a silent mutation in the protein. If you chose, 5' ATC GCA TGG TGA 3', this is incorrect because the change here (GTC to ATC in the first codon) would change a Val codon into an Ile codon. This is a point mutation in the DNA that would result in a missense mutation in the protein. Background. A point mutation (single nucleotide change in a codon) that changed the G in the second position of the third codon (TGG) into an A (TAG) changed the amino acid tryptophan (Trp) into a premature stop codon - This is a point mutation in the DNA that would result in a a nonsense mutation in the protein.

What would the amino acid sequence be from this coding strand sequence: 5'-GGA AGG CCC-3'? a. Gly Arg Pro b. Lys Pro Ser c. Pro Gly Arg d. Val Ala Pro

a. Gly Arg Pro Feedback Correct! The mRNA transcribed from the template strand is complementary and antiparallel to it. The coding strand of DNA (also called the non-template strand) is also complementary and antiparallel to the template strand. Thus, translating 5'-GGA AGG CCC-3' gives us Gly Arg Pro

The RNA sequence 5'-CUC AUA GCC UGA CCC-3' is mutated to 5'-CUC AUA GCC UAA CCC-3' What kind of mutation is this? a. Silent b. Missense c. Nonsense d. Frameshift

a. Silent Feedback If you chose, Nonsense Mutation, this is incorrect. A nonsene mutation is when a codon is changed from coding an amino acid to coding for a stop codon. For example, UGC (Cys) to UGA (stop codon), this usually causes truncated, non-functional proteins. If you chose, Missense Mutation, this is incorrect. A missense mutation changes the codon to code for a different amino acid. For example, if we changed UUC (Phe) to UUA (Leu). If you chose, Frameshift, this is incorrect. Frameshift mutations are not point mutations and are usually the result of an insertion or deletion. As such, inserting or deleting nucleotides will change the number of nucleotides present causing a shift in the reading frame. For example, if we read the sentences CAT HAT DOG and deleted the 'A' in CAT we would change the reading frame to CTH ATD OG. Background. The A in the second position of the third codon is mutated to a G, changing the codon from UAA to UGA. This changes one STOP codon into another STOP codon, so there is a STOP codon where there should be a STOP codon. This is not a premature STOP codon. Since the amino acid sequence doesn't change, this a silent mutation.

Tissues at rest have an oxygen concentration of 40 Torr. What is the fraction of hemoglobin with oxygen bound (hemoglobin saturation) at 40 torr and at pH 7.2? a. 0.2 b. 0.5 c. 0.8

b. 0.5 Feedback Correct! Starting at the 40 torr mark, going straight up to the first curve which is the pH 7.2 curve, and then straight to the left, you would cross the vertical axis at about 0.5, or 50%.

If one strand of chromosome 2 has a DNA sequence that consists of this: 5' AAG CGG TAC GTA 3' What will be the composition of the complementary DNA strand? (Select all that apply) a. 5' TTC GCC ATG CAT 3' b. 3' TTC GCC ATG CAT 5' c. 5' TAC GTA CCG CTT 3' d. 3' AAG CGG TAC GTA 5'

b. 3' TTC GCC ATG CAT 5' c. 5' TAC GTA CCG CTT 3' Feedback Correct! All complementary base pairing must be antiparallel. The complementary strand to 5' AAG CGG TAC GTA 3' is 3' TTC GCC ATG CAT 3'. If we simply 'flip' the sequence, we get 5' TAC GTA CCG CTT 3'. Thus, these are the correct answers.

What would be the resulting mRNA sequence from a template strand with this sequence: 5'-CAG CTC GTC-3'? a. 5'-GUC GAG CAG-3' b. 5'-GAC GAG CUG-3' c. 3'-GAC GAG CUG-5' d. 3'-GUG GAG GAG-5'

b. 5'-GAC GAG CUG-3' Feedback Correct! Sequences that bind each other (are complementary) must also be antiparallel (running in opposite directions). The sequence that is complementary to 5'-CAG CTC GTC-3' is 3'-GUC GAG CAG-5'. Since the possible answers in the list to choose from are presented with their 5' ends on the left, we simply 'flip' the sequence to get 5'-GAC GAG CUG-3'.

Which of the following is NOT a step in base excision repair? a. Ligation to restore continuity of the DNA backbone b. Synthesis of an RNA primer c. Recognition of the damage d. Removal of the damage by excising part of one strand to leave a gap

b. Synthesis of an RNA primer Feedback Synthesis of an RNA primer is part of DNA replication, not DNA repair.

A patient with xeroderma pigmentosum is prone to developing multiple skin cancers starting in childhood. This occurs because of a mutation in a gene that codes for enzymes that help repair DNA damage through the nucleotide excision repair (NER) pathways. How does NER differ from other repair mechanisms? In NER: a. Only one nucleotide is removed and DNA polymerase replaces the one abnormality b. The error in one strand of DNA is removed as well as several nucleotides on either side of the error. The gap that was removed is filled in by DNA polymerase c. The entire homologous chromosome is used to repair the double stranded DNA error d. The affected DNA strand and its complementary strand is discarded and a new double stranded DNA is created

b. The error in one strand of DNA is removed as well as several nucleotides on either side of the error. The gap that was removed is filled in by DNA polymerase Feedback Correct! Nucleotide excision repair replaces several damaged nucleotides plus additional nucleotides and uses the DNA on the opposite strand as a template to fill in the gap.

The structure of fetal hemoglobin allows it to have a higher affinity for oxygen when compared to maternal hemoglobin. Which of the following accurately describes fetal hemoglobin? binds oxygen tightly at lower oxygen concentrations identcal polypeptide chains as adult hemoglobin is never in the R-state exhibits an oxygen binding curve that is the same shape as myoglobin oxygen binding curve.

binds oxygen tightly at lower oxygen concentrations Feedback Correct! Fetal hemoglobin is preferentially in the R-state and is capable of binding oxygen at lower oxygen concentrations. This allows fetal hemoglobin to receive oxygen from maternal hemoglobin.

The following sequence is the coding DNA strand of the collagen gene: 5' ATG GCG TTC GAA 3' What is the sequence of the corresponding mRNA? a. 3' ATG GCG TTC GAA 5' b. 5' AUG GCG UUC CUU 3' c. 5' AUG GCG UUC GAA 3' d. 5' UTG GCG TTC GUU 3'

c. 5' AUG GCG UUC GAA 3' Feedback Correct. The coding strand and the mRNA both go in the same direction, but do not both contain Ts.

If the coding (non-template) DNA sequence of a normal gene is 5' GTC GCA TGG TGA 3', which DNA sequence would represent a deletion mutation? a. 5' GTC GCA TAG TGA 3' b. 5' ATC GCA TGG TGA 3' c. 5' GTC GCA TGT GA 3' d. 5' GTA GCG TGG TGA 3'

c. 5' GTC GCA TGT GA 3' Feedback Correct! A deletion mutation removed a G from the fourth codon (TGG). Notice that there are now fewer nucleotides in the mutant gene compared to the normal gene.

Which of the following does not bind directly to hemoglobin? a. O2 b. CO c. CO2 d. H+ e. 2,3 BPG

c. CO2 Feedback Correct! Carbon dioxide does not bind directly to hemoglobin, whereas oxygen, carbon monoxide, H+ and 2,3-BPG are all able to bind directly to the protein.

What is the coding strand sequence if the non-template strand sequence is 5'-AGC CTT TAA CTA-3' a. 5'-TCG GAA ATT GAT-3' b. 5'-TAG TTA AAG GCT-3' c. 3'-AGC CTT TAA CTA-5' d. 3'-ATC AAT TTC CGA-5'

d. 3'-ATC AAT TTC CGA-5' Feedback Correct! The names "coding strand" and "non-template strand" refer to the exact same piece of DNA. Therefore, if the non-template strand is 5'-AGC CTT TAA CTA-3', then the coding strand is exactly the same sequence (because it is the same piece of DNA: 3'-ATC AAT TTC CGA-5'.

What would be the amino acid sequence that would result from this template sequence: 5'-TGC AAG CCA-3'? a. Pro Leu Trp b. Thr Phe Gly c. Gly Phe Thr d. Trp Leu Ala

d. Trp Leu Ala Feedback Correct! The RNA polymerase enzyme makes mRNA by antiparallel and complementary basepairing with the template strand of DNA. Therefore, the mRNA transcribed from this template would be 3'—ACG UUC GGU-5'. mRNA codons are read 5' --> 3' on the genetic code table. 'Flipping the sequence gives us 5'-UGG CUU GCA-3'. Using the genetic code table, we see that UGG encodes Trp; CUU encodes Leu; and GCA encodes Ala.

If consuming a no-fat diet, one could suffer from poor wound healing response. This is primarily due to a lack of ___. triglycerides phospholipids essential fatty acids cholesterol

essential fatty acids Feedback Correct! Lack of essential fatty acids can lead to poor wound healing.

One way a cell can avoid overproduction of a molecule is by using a particular type of inhibition in which this same molecule acts as an inhibitor for an enzyme in its production pathway. This type of regulation is known as ___________ inhibition. regulatory feedback specific allosteric

feedback Correct! Feedback. Background information: Feedback inhibition, a kind of reversible noncompetitive inhibition, regulates the rate of many metabolic pathways. When the end product of a pathway is needed by the cell and consumed by cellular reactions, the pathway remains active. When the end product is no longer needed by the cell, the end product ceases to be consumed and begins to accumulate. Upon accumulation of the end product, it binds to the first enzyme in the pathway and initiates the inhibition of the pathway. The inhibition of the first enzyme in the pathway decreases the activity of each subsequent pathway intermediate. When the product concentration falls, there would no longer be inhibition of the first enzyme in the pathway and the pathway could resume its production of the end product again. While feedback inhibition often targets the first step in a biochemical pathway, this type of inhibition can occur for any step in the pathway. The end product will target the most important step in a biochemical pathway.

Carbon monoxide outcompetes oxygen for attachment to the __________ group of hemoglobin where it is permanently, covalently attached. heme ligand sulfide histidine

heme Feedback Correct! Carbon monoxide and oxygen bind hemoglobin by binding to the heme group at the center of the protein.

In the organization of DNA into chromosomes, DNA is wrapped around _________ to form nucleosomes. Nucleosomes are organized further to form _____________. RNA; triple helix histones; nucleus histones; chromatin promoters ; histones

histones; chromatin Feedback Correct! DNA is wrapped around proteins called histones to prevent tangling, and the combination of DNA and histone proteins creates nucleosomes. The histones promote coiling of the nucelosomes into a larger chromatin fiber.

Patients with sickle cell anemia have atypical hemoglobin, which will distort the red blood cells into sickle shape during oxygen delivery. The substitution of a hydrophilic amino acid with a ____________amino acid in hemoglobin subunits results in the polymerization of hemoglobin, leading to the sickling of red blood cells. polar cysteine hydrophilic hydrophobic

hydrophobic Feedback Correct! In Sickle Cell Anemia, the beta hemoglobin gene contains a mutation where glutamate is changed to valine (a hydrophobic amino acid), which affects the hydrophobic patches of deoxygenated hemoglobin.

Which of the following forces can lead to aggregation as a result of protein misfolding? disulfide bonds hydrogen bonds ionic bonds hydrophobic interactions

hydrophobic interactions Feedback Correct! Misfolded proteins can have sections of hydrophobic amino acid residues exposed to water. This can lead to misfolded proteins to aggregate in order to form favorable hydrophobic interactions between nonpolar amino acids in adjacent protein chains and to keep these hydrophobic residues away from water.

When oxygen is low, muscle and liver cells can participate in the Cori Cycle in which the muscle cells produce ________ which is then converted to ________ in the liver. lactate, glucose pyruvate, lactate glucose, lactate glucose, pyruvate

lactate, glucose Feedback Correct! During anaerobic metabolism, muscles convert pyruvate to lactate and the liver uses this lactate to create glucose.

The dietary absorption of fat-soluble vitamins requires phospholipids in the form of ______. cell membranes micelles essential fatty acids eicosanoids

micelles Feedback Correct! Micelles are composed of phospholipids. Micelles can hold fat-soluble vitamins.

Which of the following interactions can occur between two positively charged amino acids? hydrogen bond hydrophobic interaction disulfide bond ionic bond none of these

none of these Feedback If you selected none of these, you are correct. Two positively charged amino acids would repel each other. Only opposite charged attract.

Which of the following interactions involve a covalent bond? (check all that apply) peptide bond hydrogen bond hydrophobic interaction ionic bond disulfide bond

peptide bond disulfide bond Feedback Correct! A covalent bond is a bond between to atoms involving the electrons being shared between them. In proteins, these include peptide bonds and disulfide bonds.

Due to their amphipathic nature, phospholipids can form micelles and transport other lipids. The fatty acid chains that make up the phospholipids are the basis for their non-polar character, and the __________ is/are the basis of its polar nature. double bonds glycerol backbone phosphate group fatty acid

phosphate group Feedback Correct! The phosphate head groups are polar.

The negatively charged amino acid, Glutamate, is replaced with the negatively charged amino acid Aspartate. Which level of protein structure is most significantly impacted by this change? primary structure secondary structure tertiary structure quaternary structure

primary structure Feedback Correct! The original and substitute amino acid both have a negative charge and can both form an ionic bond with a positively charge amino acid, so contributions to quaternary and tertiary structure, which are dependent on side-chain interactions, are most likely unaffected. The secondary structure of a protein depends on backbone interactions, and is also probably unaffected. The amino acid sequence, however, has been altered, and so the primary structure has certainly been changed.

Two healthy individuals give birth to a child that has Bloom Syndrome. From this information, it can be concluded that Bloom syndrome is inherited in a ________ manner. recessive dominant sex-linked

recessive Feedback Carrier parents are parents who do not have a particular trait, such as a disease, but that trait shows up in their offspring. The presence of carrier parents signifies that the trait is recessive.

A mutation in the DNA that changes the sequence of a codon but does NOT change the amino acid sequence of the protein describes a _____ _____. frameshift mutation. missense mutation. nonsense mutation. silent mutation.

silent mutation. Feedback -If you chose 'Frameshift Mutation', this is incorrect. Errors that increase or decrease the number of nucleotides in a gene cause frameshift mutations. The insertion of an extra base or the removal of one of the bases will change which groups of three bases that the ribosome reads when it translates the message. This is said to 'shift' the 'reading frame' from the correct groups of three bases to different groups. To visualize what a frameshift is, imagine you are given a string of letters and told to start at the beginning and read every group of three letters: CATDOGRATPIGAPE. You would get "cat dog rat pig ape". But if we add an extra letter, say CATDFOGRATPIGAPE, following our "read every group of three" rule, we would get "cat dfo gra tpi gap e". Shifting our 'reading frame' by adding one more letter completely changes what we read. This is similar to what happens with a frameshift mutation. -If you chose 'Missense Mutation',this is incorrect. A single nucleotide change in the DNA (point mutation ) that changes a codon in the mRNA such that it codes for a different amino acid, changes one amino acid in the amino acid sequence of a protein. This is called a missense mutation. See Figure 1-19 in the Module 1 text for more information. - If you chose 'Nonsense Mutation', this is incorrect. A single nucleotide change in the DNA (point mutation ) that changes a codon in the mRNA from one that codes for an amino acid into one that specifies the STOP signal is a nonsense mutation. The protein will terminate prematurely. Background: When a point mutation (single nucleotide change) occurs it changes the mRNA codon (triplet sequence that codes for amino acid), however, it doesn't affect the amino acid it codes for. For example, if a point mutation caused UUU (codes for Phe) to change to UUC- this is a silent mutation as both codons (UUU and UUC) code for Phe.