Biochem Quizzes Modules 1-4
The Central Dogma can be summarized as ______ makes ______ makes ______ .
DNA RNA protein
RNA viruses are an exception to the Central Dogma. True False
False
____________ is a test solution used to identify reducing and nonreducing sugars.
Fehling's
The amino acid histidine has 3 hydrogens that could be titrated with pK values of 1.82, 6.0, and 9.17. Describe the pH ranges in which histidine could be used as a buffer and explain why histidine might be a good candidate for buffering the intracellular pH of cells.
Histidine could be used as a buffer in pH ranges 0.82 to 2.82; 5.0 to 7.0; and 8.17 to 10.17 (pH ranges -/+1 from each pK value). Histidine might be a good candidate for buffering the intracellular pH of cells, because its pH range of 5.0 to 7.0 is close to the intracellular pH of cells, 6.7 to 7.4.
Why are some amino acids considered essential amino acids? They are essential to humans' sense of smell. Human cells cannot synthesize them. They require further modification by human cells for protein synthesis. They are used in only a subset of proteins synthesized in human cells. None of the above.
Human cells cannot synthesize them.
Hair can be reshaped into curls or straightened in a process called "perming". One way this is done is by treating hair with a chemical called ammonium thioglycolate, which is a reducing agent, followed by wrapping the the hair around a curler or ironed out straight by flatirons. After the hair has been reshaped it is treated with an oxidizing agent to stabilize the new shape. What amino acids are these chemical treatments affecting and how do they allow hair to be reshaped?
In a perm, chemical treatments affect the amino acid cysteine. Hair is mainly made up of the protein keratin, which contains a lot of cysteine amino acids. Cysteine has sulfur in its functional group. Cysteines form disulfide bonds between one another, keeping keratin molecules in place. The chemical reducing agent works to break these disulfide bonds, allowing the keratin molecules to reshape around the curler. The oxidizing agent creates new disulfide bonds which maintain the new curled shape of the hair.
Why is pure water neutral and at a pH = 7?
In freshly distilled water, there is an equal concentration of [H^+] and [OH^-].
If noncovalent bonds are so much weaker than covalent bonds, how do they stabilize large biochemical structures?
Individually noncovalent bonds are much weaker than covalent bonds, but in great number noncovalent bonds can be much stronger than covalent bonds. In large biochemical structures, many noncovalent bonds allow for a stable, strong structure, but they are also useful for biological molecules as they can be readily broken down. This is necessary in structures like DNA that need to be held intact, but also need to be opened up for transcription and translation.
Why is the peptide bond planar? Bulky side chains prevent free rotation around the bond. It exhibits partial double-bond character, preventing rotation. Hydrogen bonding between the NH and C=O groups limits movement. None of the above All of the above
It exhibits partial double-bond character, preventing rotation.
For a solution of the weak acid HA, what are the formulas used to calculate Ka = _____________ and pKa = ______________? Ka = [H+][A-] / [HA]; pKa = log [Ka] Ka = [H+][A-] / [HA]; pKa = -log [Ka] Ka = [HA] / [H+][A-]; pKa = log [Ka] Ka = [HA] / [H+][A-]; pKa = -log [Ka] none of the above
Ka = [H+][A-] / [HA]; pKa = -log [Ka]
____________: Chiral type of amino acids found in proteins.
L amino acids
____________ are proteins that bind to specific carbohydrate structures.
Lectins
Name two amino acids that are positively charged at a neutral pH. Lysine and arginine Histidine and arginine Cysteine and arginine Lysine and proline Glutamine and histidine
Lysine and arginine
With increasing CO2 concentration in the atmosphere what would you expect would happen to the pH of lakes, rivers, and oceans?
One would predict the large bodies of water to equilibrate with atmospheric CO_2 and become more acidic.
Which of the following amino acid residues would most likely be buried in the interior of a water-soluble, globular protein? Aspartate Serine Phenylalanine Lysine Glutamine
Phenylalanine
What are the three major buffering systems used in our bodies?
Phosphate, proteins, and bicarbonate.
_______________: A transient copy of genetic information.
RNA
The plot that allows one to investigate the likely orientation of certain amino acid pairs is called the ____________.
Ramachandran
What is the difference between saturated and unsaturated fatty acids? Saturated fatty acids are bound by water whereas unsaturated fatty acids do not bind water. Saturated fatty acids have many double bonds in their hydrocarbon chains whereas unsaturated fatty acids have no double bonds in the hydrocarbon chain. Saturated fatty acids have only single bonds between the carbons in the hydrocarbon chain whereas unsaturated fatty acids have one or more double bonds between carbons in the hydrocarbon chain. Saturated fatty acids are always a solid at room temperature and unsaturated fatty acids normally exist as an oil. Saturated fatty acids are found only in plants and unsaturated fatty acids only in animal fat
Saturated fatty acids have only single bonds between the carbons in the hydrocarbon chain whereas unsaturated fatty acids have one or more double bonds between carbons in the hydrocarbon chain.
What is the Central Dogma and how can it be summarized?
The Central Dogma is a description proposed by Francis Crick of the flow of genetic information from DNA to RNA to protein. The Central Dogma states that DNA can replicate itself with the help of DNA polymerases. RNA is made from DNA through a process called transcription by RNA polymerases. Protein is made from RNA through translation and occurs on ribosomes.
When we exercise we produce CO2 and lactic acid in our muscle tissues. How do our bodies prevent wide fluctuations in blood pH from exercise?
The bicarbonate buffer helps to maintain a constant blood pH but because it's pK is over 1 pH unit from the blood pH of 7.4. Because of this our bodies have evolved a complex system to prevent build up of CO_2 concentrations in blood by expiring the excess CO_2 from our lungs, and by excreting it in our urine.
Ionic bonds, hydrogen bonds, and van der Waal's interactions are all weak bonds that form by attraction between two atoms or molecules. What is the name of the weak force that does not work by attraction? Describe why.
The name of the weak interaction is the hydrophobic effect. It works by creating more entropy in water solutions. An important example is the formation of cellular membranes between lipids that are insoluble in water. Aggregation between the long, uncharged lipid side chains releases the surrounding water molecules back into bulk water increasing the overall entropy of the system.
What is the pH range of blood?
The pH of blood is between 7.35 and 7.45.
DNA is made from the bases adenine, guanine, cytosine, and ____________.
Thymine
What fat is not a normal part of our diet? Saturated fats Poly-unsaturated fats Omega-3 fatty acids Trans fats, or fats with trans isomers around double bonds Omega-6 fatty acids
Trans fats, or fats with trans isomers around double bonds
What is the major lipid used for energy storage in our bodies? Triacylglycerides Phosphatidic acid Cholesterol Phosphoglycerides Sphingolipids
Triacylglycerides
How is water able to be a solvent for so many biological molecules?
Water is able to be a solvent for so many biological molecules because water can form hydrogen bonds with molecules that have electronegative atoms. These hydrogen bonds can disrupt the bonds of certain biological molecules, thus making water a good solvent. Water can form hydrogen bonds because water is a polar molecule with partially positive hydrogen atoms. Most biological molecules are polar.
Why are weak acids and bases good buffers and how does a buffer work?
Weak acids and bases only partially dissociate into H^+ and conjugate base. They are good buffers because in solution there is a pH = pK at which the weak acid or base is only 50% dissociated and could donate or accept hydrogen ions if a reaction in the solution used or created more H^+. Buffers work by accepting or donating H^+, when at pH = pK and preventing rapid changes in the solution pH.
If an individual weak bond can be broken at room temperature, how do weak bonds work to maintain protein and DNA structure?
Weak bonds work by strength in numbers. The energy to break hundreds or thousands of weak bonds can exceed the energy required to break a covalent bond, thus many weak bonds help maintain protein and DNA structure.
The pK of acetic acid is pK = 4.76. For a 0.1 M solution of acetic acid at a pH = 4.76 what is the concentration of [H+]?
[H+] = [CH3COO-] = 0.05 M. For solutions of weak acids and bases with a pH = pK the concentrations of H+ and OH- are equal.
All fatty acids have these structures in common: a polar carboxylic acid head and charged, polar side chain a polar carboxylic acid head and an uncharged, nonpolar hydrocarbon chain a polar carboxylic acid head and an unsaturated, nonpolar hydrocarbon chain a polar carboxylic acid head and a saturated, nonpolar hydrocarbon chain a polar phosphate head and an uncharged, nonpolar hydrocarbon chain
a polar carboxylic acid head and an uncharged, nonpolar hydrocarbon chain
Give 8 examples of key functional groups found in biochemistry.
aldehydes, ketones, carboxylic acids, phenyls, amines, alcohols, phosphates, thiols
Which of the following is considered a noncovalent bond? electrostatic interactions hydrogen bonds van der Waals interactions all of the above none of the above
all of the above
According to convention, ____________ is the terminus drawn on the left side of a peptide.
amino
An example of primary structure in a protein: An example of secondary structure in a protein: An example of protein motif:
amino acid sequence alpha-helix helix-turn-helix
Lipids that interact with both the water and the hydrophobic regions of the membrane are considered ____________.
amphipathic
____________: A term applied to molecules that have both hydrophilic and hydrophobic moieties.
amphipathic
The key buffering component of blood is _______________________ and the source of this key component is _______________________.
bicarbonate or H2CO3/HCO3- carbon dioxide or CO2
Why are chicken fat, lard, and butter all solids at room temperature while canola oil and olive oil are liquids? chicken fat, lard, and butter all come from animal and dairy products. canola and olive oils have more unsaturated and short chain fatty acids. chicken fat, lard, and butter have more protein and suspended solids. chicken fat, lard, and butter are fats, not oils chicken fat, lard, and butter have more cholesterol.
canola and olive oils have more unsaturated and short chain fatty acids.
____________: Disulfide bonds are formed by pairs of this amino acid.
cysteine
The 4 deoxyribonucleoside triphosphates found in the cell are:
dATP, dCTP, dGTP, and dTTP
Hydrophobic molecules are driven together by ____________, not because they have an affinity for each other.
entropy
____________: Thermodynamic force that drives hydrophobic interactions.
entropy
____________: Monosaccharides that differ at a single asymmetric carbon.
epimers
____________: An amino acid that must be supplied by the diet.
essential
____________: The storage form of glucose in animals.
glycogen
____________________ is a branched starch molecule use for storage of glucose in muscle tissue.
glycogen
____________: The type of bond found between an oxygen on one water molecule and hydrogen on a different water molecule.
hydrogen
The unusually high surface tension property of water that allows water striders to "walk" on water is due to ___________________________________.
hydrogen bonding networks
What is the central dogma? A hypothesis proposed by Francis Crick to describe the genetics of dogs A hypothesis proposed by Francis Crick to describe how DNA is replicated A hypothesis proposed by Francis Crick and James Watson describing the structure of DNA hypothesis proposed by Francis Crick to describe the flow of information from DNA to protein hypothesis proposed by Francis Crick to describe the flow of information from protein to DNA
hypothesis proposed by Francis Crick to describe the flow of information from DNA to protein
The weak van der Waal's force creates its own attractive force between atoms due to _____________ _____________ formed by repulsion between electrons.
induced dipoles
What are prions? an intracellular organelle used for protein degradation proteins located on virus capsids infectious disease causing proteins cancer specific proteins a self replicating protein
infectious disease causing proteins
The class of glycoproteins made up of a core protein linked through a serine or threonine to carbohydrates that is made in large amounts in humans infected by the common cold virus is called _________________.
mucins
A nitrogen containing an aromatic base attached to a ribose is a __________________.
nucleoside
Buffers are critical in maintaining proper ____________ levels in biological systems.
pH
If you have a solution that is a pH of 3.6 what is the pOH and what is pOH measuring?
pH + pOH = 14 thus the pOH would be 10.4. Similar to pH, the pOH measures the hydroxyl ion concentration in solution. If a solution is acidic then you would expect there to be few OH- ions and thus present in a very low concentration. A pOH of 10.4 is equal to [OH^-] = 4 x 10^-11 M!
What is the formula used to calculate pH?
pH = -log [H^+]
Write the Henderson-Hasselbalch equation.
pH = pKa + log([A-]/[HA])
Molecules that are readily soluble in water are considered ____________.
polar
____________: The charge of an amino group when the pH is one pH unit below the pKa.
positive
The four levels of protein structure are:
primary, secondary, tertiary, and quaternary
____________: This amino acid residue disrupts the α helix because its side chain contains a unique ring structure that restricts bond rotations.
proline
Changes in ____________ create amyloid fibers which are insoluble and are the source of mad cow disease, and Alzheimer's, and Parkinson's diseases.
secondary structure
____________: The type of structure to which α helices, β sheets, and turns are referred.
secondary structure
_______________ is a simple motif of RNA structure.
stem loop
A disaccharide made of the monosaccharides glucose and fructose is: maltose amylose sucrose lactose saccharin
sucrose
The axis of a double helix can be over-wound by a mechanism called ____________________.
supercoiling
The overall structure of an individual protein is referred to as ____________.
tertiary structure
The configuration of most α-carbon atoms of amino acids linked in a peptide bond is: cis circular parallel trans perpendicular
trans
The transfer of information from DNA to RNA is called ____________.
transcription
The distance when two atoms no longer repulse each other yet have the strongest attraction is known as the____________ radii or contact distance.
van der Waals
The chemical forces that contribute to the stability of the DNA due to the base stacking present in the DNA helix are hydrogen bonds. van der Waals interactions. disulfide bonds. A and C None of the above
van der Waals interactions.
What is the working pH range above and below the pKa for most buffers? 0.5 pH units 1 pH unit 1.5 pH units 3 pH units 2.5 pH units
1 pH unit
Sea water is about ______________ times more basic than black coffee.
1,000
Individual weak bonds are approximately __________-fold weaker than strong covalent bonds.
10
There are approximately __________________ bases per turn of a B-DNA double helix.
10
What is the H+ concentration in a urine sample that has a pH of 6? 10-6 M 10-8 M 106 M 10-14 M 8 M
10-6 M
What is the [A−]/[HA] ratio when the weak acid is in a solution one pH unit above its pKa? 1:1 1:10 10:1 2:1 none of the above
10:1
____________: The number of hydrogen bonds formed between G and C.
3
What is the pH of a solution that is a concentration of 3.2 x 10-5 M H+? 3.2 4.5 5.3 3.5 2.3
4.5
What is the complementary DNA sequence for 5′-GACTCTTGGTAT-3′? 5′-GACTCTTGGTAT-3′ 5′-CTGAGAACCATA-3′ 5′-ATACCAAGAGTC-3′ 5′-TATGGTTCTCAG-3′ 5′-ATAGGAACAGAG-3′
5′-ATACCAAGAGTC-3′
What is the complementary sequence to 5′-AAGCTTCCGGATATG-3′? 5′-AAGCTTCCGGATATG-3′ 5′-TTCGAAGGCCTATAC-3′ 5′-CATATCCGGAAGCTT-3′ 5′-GTATAGGCCAACGAA-3′ 5′-AAGCTTCCGGATATG-3′
5′-CATATCCGGAAGCTT-3′
What is the H+ concentration in a urine sample that has a pH of 7.2? 7.2 x 10−7 M 1.6 x 107 M 6.3 x 10-8 M 10−14 M 8.6 x 10-1 M
6.3 x 10-8 M
What charged group(s) are present in glycine at a pH of 7? -NH3+ -COO- -NH2+ A and B A, B, and C
A and B
What charged group(s) are present in glycine at a pH of 7? -NH3+ -COO- -NH2+ A and B A, B, and C
A and B
What charged group(s) is/are present in glycine at a pH of 7? NH3 COO NH2 A and B A, B, and C
A and B
Which processes does the Central Dogma rule out? Making RNA or DNA from protein Making protein directly from DNA without an RNA intermediate Making RNA from DNA A and B B and C
A and B
How does a nucleotide differ from a nucleoside? Nucleosides are found in DNA, whereas nucleotides are found in RNA. Only nucleotides contain purines. Nucleosides contain only deoxyribose sugars. A nucleotide is a nucleoside with a phosphate ester linked to the sugar. None of the above
A nucleotide is a nucleoside with a phosphate ester linked to the sugar.
What are the normal functions of cholesterol in our bodies? Manage membrane fluidity Synthesize vitamin D Synthesize testosterone and progesterone A and C A, B, and C
A, B, and C
Which of the following statement/s accurately describe/s properties of prions? Prions cause misfolding of other proteins Prions cause toxic networks of misfolded proteins Prions can be transmitted by ingestion of prion-contaminated food A, B, and C none of the above
A, B, and C
Water can form hydrogen bonds with the _______________________ of another molecule. carbonyl groups amine groups aromatic groups alcohol groups A, B, and D
A, B, and D
What are the four bases found in RNA?
A, G, C, U
Describe the relationship between fatty acid chain length, saturation, and the melting point or fluidity of fatty acids.
All fatty acids have a polar carboxylic acid head group and an uncharged, nonpolar hydrocarbon chain. Fatty acid hydrocarbon chains vary in the number of double bonds, if any, are present in the chain. A fatty acid chain is said to be unsaturated if it has one or more double bonds, and it is said to be saturated if it has no double bonds. Both fatty acid chain length and degree of saturation affect fatty acid melting point. As chain length and saturation increase, melting temperature increase, and as chain length and saturation decrease, melting temperature decreases. This is because the longer and more saturated the chain, the easier it is for the chain to tightly pack together with other fatty acid chains, acting more as a solid than a liquid at room temperature. The double bonds in unsaturated chains introduce kinks in the chain which weaken intermolecular interactions.
The feature(s) of DNA deduced by Watson and Crick include: two antiparallel polynucleotide chains coiled in a helix around a common axis. that the pyrimidine and purine bases lie on the inside of the helix. that the bases are nearly perpendicular to the axis. All of the above None of the above
All of the above
List atoms commonly found in biological molecules that are often hydrogen-bond acceptors. carbon oxygen nitrogen B and C All of the above
B and C
List atoms commonly found in biological molecules that are often hydrogen-bond acceptors. carbon oxygen nitrogen B and C all of the above
B and C
What amino acids are not found in a-helices? Leucine Proline Glycine A and B B and C
B and C
What are the two essential fatty acids we need to get in our diet? Stearidonic acid or all-cis-6,9,12,15-octadecatetraenoic acid α-Linolenic Acid and ω-3 fatty acid Linoleic Acid and ω-6 fatty acid A and C B and C
B and C
The ____________ form of DNA is the predominant form in cells.
B-DNA
