Biology Semester review

The movement of sodium and potassium across a cell membrane is a passive process 1.True 2.False

false

Which of the following questions will best direct an investigation of the mechanism of ATP synthase? 1. Is the phosphorylation by ADP by ATP synthase dependent on the formation of a proton gradient. 2. What is the source of the inorganic phosphate that is used to generate ATP from ADP? 3. Can oxidative phosphorylation be uncoupled from the electron transport chain? 4. Can ATP synthase use the energy released by phosphorylation of ADP to pump protons against a concentration gradient?

1. Is the phosphorylation by ADP by ATP synthase dependent on the formation of a proton gradient.

In a certain signal transduction pathway, the binding of an extracellular molecule to a cell-surface protein results in a rapid increase in the concentration of cyclic AMP inside the cell. The cyclic AMP binds to and activates cytosolic enymes that then activte other enzymes in the cells. Which of the following statements best describes the role of cyclic AMP in the signal tranduction pathway? 1. It acts as a second messsenger that helps relay and amplify the signal within the cell. 2. It acts as a receptor that carries the signal from outside the cell to inside the cell. 3. It acts as a channel protein that transmits the signal across the cell's nuclear membrane. 4.It acts as a signaling molecule that passes the signal from the cell to other cells.

1. It acts as a second messsenger that helps relay and amplify the signal within the cell.

What statement describes the function of photosystem II? 1. Light energy excites electrons in the thylakoid membrane electron transport chain 2.The splitting of water yields molecular carbon dioxide as a by-product. 3.The P680 chlorophyll donates a pair of protons to NADP+, which is converted to NADPH 4.Photons are passed along to a reaction center

1. Light energy excites electrons in the thylakoid membrane electron transport chain

Process in which O2 is released as a by-product of oxidation-reduction reactions 1. Light-dependent reactions of photosynthesis 2. Krebs cycle (citric acid cycle) 3. Calvin cycle (light-independent reactions of photosynthesis) 4. Glycolysis

1. Light-dependent reactions of photosynthesis

An intermediate electron acceptor for oxidations that occur in both glycolysis and in Krebs cycle reactions 1. NAD+ 2. Oxygen (O2) 3. FADH2 4. Cytochrome

1. NAD+

Thyroxine is a hormone that increases metabolic activities within various tissue targets. Low levels of circulating thyroxin trigger the secretion of thyroid-stimulating hormone (TSH) from the anterior pituitary. TSH secretion then stimulates thyroxin production adn release by the thyroid gland. The increased level of circulating thyroxin inhibits further secretion of TSH from the anterior pituitary. Based on the information above, whic hof the following can most likely be concluded about the TSH-thyroxin loop? 1. The feedback mechanism would maintain relatively constant levels of thyroxin throughout the tissue targets. 2. The structure of the loop would lead to elevated thyroid and tissue activity due to positive feedback 3. A person taking thyroxin to supplement low thyroxin secretion will produce more TSH 4. Increased thryoxin production would cause elevated ribosomal activity in the anterior pituitary

1. The feedback mechanism would maintain relatively constant levels of thyroxin throughout the tissue targets.

A researcher designs an experiment to investigate the effect of environmental temperature on the function of an enzyme. For each trial included in the experiment, the researcher will add the enzyme and its substrate to an aqueous buffer solution and then measure the amount of product formed over 20 minutes. Which of the following must remain the same for all trials of this experiment? 1. The initial concentration of the substrate 2. The temperature of the aqueous buffer solution 3. The three-dimensional structure of the enzyme 4. The final concentration of the product

1. The initial concentration of the substrate

Which of the following best describes the structures of carbohydrates? 1. They occur as monomers, polymers, and branched structures. 2. They occur as chains of monomers that hydrogen bond with complementary chains of monomers. 3. They only occur as long and branched structures. 4. They only occur as disaccharides.

1. They occur as monomers, polymers, and branched structures.

A collection of nucleotides could be used to build a... 1.Nucleic Acid 2.Protein 3.complex carbohydrate 4. triglyceride

1. nucleic acid

Damaged tissue release chemicals that activate platelets and stimulate the formation of blood clots. Which of the following predictions about the activity of platelets best describes a positive feedback mechanism? 1. Activated platelets release chemicals that activate more platelets 2. Activated platelets release chemicals that inhibit blood clot formation. 3. Activated platelets constrict the blood vessels, stopping blood flow 4. Activated platelets release signaling molecules that inhibit cell division in damaged tissue.

2. Activated platelets release chemicals that inhibit blood clot formation.

Gelatin is a protein that is derived from collagen which is found in the bones, skin, and connective tissue of animals. To investigate the ability of various enzymes to digest gelatin, a group of students set up an assay (a test) involving camera film. Camera film contains gelatin and appears black when exposed to light but turns clear as the gelatin gets broken down. The students incubated pieces of exposed camera film in test tubes, each containing one of three different enzyme solutions (trypsin, lipase, or amylase) as indicated in Figure 1. The students recorded the time it took for the enzymes to digest the gelatin in each test tube, turning the film from black to clear. Which of the following would be the most appropriate control for this experiment? HINT: Ask yourself what is the control group of an experiment? 1.A test tube containing a piece of exposed camera film submerged in water 2.A test tube containing no camera film 3. A test tube containing only a piece of exposed camera film 4. A test tube containing a piece of exposed camera film and all three enzyme solutions

1.A test tube containing a piece of exposed camera film submerged in water

The model above represents the role of two hormones, calcitonin and parathyroid hormone (PTH), in maintaining normal blood calcium levels in humans. If a dietary change results in an increase in blood calcium above normal levels, which of the following is the most likely effect on calcium homeostasis? 1.Calcitonin levels will decline, thus stimulating the release of PTH 2. PTH levels will decline, thus stimulating the loss of calcium from bones. 3. Calcitonin levels will rise, thru promoting the deposit of calcium into bones 4. PTH levels will increase, thus preventing the release of calcitonin

1.Calcitonin levels will decline, thus stimulating the release of PTH

How will brief heating (to 95 degrees C) affect macromolecular structures in aqueous solution? 1.Proteins will unfold (denature) 2.Starch will hydrolyze into monomeric sugars 3.unsaturated fatty acid tails will become saturated. 4.Proteins will hydrolyze into amino acids

1.Proteins will unfold (denature)

The figure above shows an organelle typically found in eukaryotic cells. Which of the following best describes the function of the double membrane system of this organelle? 1.The inner membrane has specialized proteins that create a hydrogen ion concentration gradient between the intermembrane space and the matrix. 2. The toxins and wastes entering a cell cross the outer membrane and are detoxified by digestive enzymes stored within the intermembrane space. 3. The outer membrane allows the transport of all molecules into the intermembrane space, while the inner membrane serves as the regulatory boundary. 4. The outer membrane contains transport proteins that establish a sodium ion concentration gradient used for ATP production, while the inner membrane contains transport proteins that establish a hydrogen ion concentration gradient used for glucose production.

1.The inner membrane has specialized proteins that create a hydrogen ion concentration gradient between the intermembrane space and the matrix.

What is the expected percentage change in DNA content of a typical eukaryotic cell as it progressessthrough the cell cycle from the start of G1 to the end of G2 phase? 1. -50% 2. +100 % 3. -100% 4. +50%

2. +100 %

The energy required to run the Calvin cycle reactions of photosynthesis comes from which two substances produced during the light-dependent reactions? 1. O2 and CO2 2. ATP and NADPH 3. H2O and CO2 4. ADP and PO4

2. ATP and NADPH

The figure below shows the relative concentrations of both the cyclin and CDK componenst of MPF. Maturation promoting factor, MPF, is a cyclin-CDK complex that catalyzes the phophorylation of other proteins to start mitosis. The activity level of MPF is dependent on the relative concentrations of the cyclin and CDK components of MPF. Based on the Figure, which of the following describes the role of cyclin in the regulation of the cell cycle. 1. During G1 phase, the cyclin level dereases to signal the start of the resting pahse of the cell cycle 2. During M phase, the cyclin level peaks, resulting in an increased binding frequency with CDK. 3. During G2 phase, the cyclin level remains low, causing MPF activity to decrease, which leads cells to initiate mitosis. 4. During S phase, the cyclin level remains the same because DNA replication is occuring

2. During M phase, the cyclin level peaks, resulting in an increased binding frequency with CDK.

The figure above is a model of an endocrine signaling pathway showing involved body parts and hormones. GnRH = gonadotropin-releasing hormone, LH = luteinizing hormone, FSH = follicle-stimulating hormone. The figure shows a model of the endocrine signaling pathway that regulates ovulation. Which of the following observations would provide evedence of a positive of a positive feed back mechanisms in this system? 1. Progesterone from the ovaries inhibits the release of LH and FSH from anterior pituitary. 2. Estrogen from the ovaries stimulates the hypothalamus and anterior pituitary to screte more GnRH, LH, and FSH 3. Estrogen from the ovaries inhibits the release of GnRH from the hypothalamus 4. Progesterone from the ovaries stimulates the thickening of the uterine lining

2. Estrogen from the ovaries stimulates the hypothalamus and anterior pituitary to screte more GnRH, LH, and FSH

The enzyme hexokinase catalyzes the conversion of glucose to glucose-6-phosphate, which is an important step in glycolysis. The reaction involves the transfer of a phosphate group from ATP to glucose. Either a glucose molecule or a water molecule can fit in the active site of hexokinase. The presence of a water molecule in hexokinase's active site would result in the hydrolysis of ATP to ADP instead of the conversion of glucose to glucose-6-phosphate. Which of the following statements best helps explain the reaction specificity of hexokinase? 1. Glucose is an energy-rich organic molecule that can be broken down by glycolysis to produce ATP, where as water is an organic molecule. Awhereas water is an inorganic molecule. 2. Glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not. 3. Both glucose and water have oxygen atoms that can form covalent bonds with the phosphorus atoms of phosphate groups. 4. Both glucose and water are polar molecules that form favorable interactions with charged and polar amino acid side chains in hexokinase's active site.

2. Glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not.

A solution, that when surrounding a cell, will cause the cell to lose water. 1. Isotonic 2. Hypertonic 3. Hypotonic

2. Hypertonic

Where precisely in the cell do the reactions of the Krebs Cycle take place? 1. cytoplasm 2. In the fluid matrix of the mitochondria 3.Surface of the cristae 4. in the space between the inner and outer membrane of the mitochondria

2. In the fluid matrix of the mitochondria

The epinphrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the bindin of the epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in the figure below: Based on the figure, which of the following statements best describes the epinephrine signaling pathway? 1. It involves changes in the expression of target genes. 2. It involves enzymes activating other enzymes 3. It involves the opening and closing of ion channels 4. It involves protons moving down a concentration gradient.

2. It involves enzymes activating other enzymes

The difference in electrical charge (voltage) across a cell's plasma membrane due to the differential distribution of ions; affects the activity of excitable cells and the transmembrane movement of all charged substances. 1. Facilitated diffusion 2. Membrane Potential 3. Electrochemical gradient 4. Proton Pump

2. Membrane Potential

A nutritional supplement developed for athletes is shown to contain only carbon, hydrogen, nitrogen, oxygen, and sulfur. Based on this data, you may safely conclude that 1. the food may contain carbohydrates, lipids, and phospholipids 2. The food may contain carbohydrates, lipids, and proteins 3. the food may contain carbohydrates, lipids, and nucleic acids 4. the food may contain carbohydrate, lipids, and not proteins

2. The food may contain carbohydrates, lipids, and proteins

Which of the following statements best helps explain the reaction specificity of an enzyme? 1. The concentration of the enzyme inside living cells is greater than the concentration of substrate. 2. The shape and charge of the substrates are compatible with the active site of the enzyme. 3. The equilibrium constant of the reaction is much greater than 1. 4. The free energy of the reactants is greater than the free energy of the products.

2. The shape and charge of the substrates are compatible with the active site of the enzyme.

The sequence 5'-GAACUT-3' may be found in which of the following? 1. either DNA or RNA 2. neither DNA or RNA 3. RNA only 4.DNA only

2. neither DNA or RNA

The NADPH required for the Calvin cycle comes from 1. reactions initiated in photo-system II 2. reactions initiated in photo-system I 3. the citric acid cycle 4. oxidative phosphorylation

2. reactions initiated in photo-system I

When a plant is wilting it is referred to as 1.Osmoregulated 2.Flaccid 3.In plasmolysis 4. Turgid

2.Flaccid

The final electron acceptor in aerobic respiration is 1.FADH2 2.Oxygen 3. Cytochrome 4. NADH

2.Oxygen

The figures below illustrate the similarities between ATP synthesis in mitochondria and chloroplasts. The figures can best assist in answering which of the following questions? 1. What is the evolutionary relationship between the ATP synthase in mitochondria and the ATP synthase in chloroplasts? 2. What are the sources of energy that drive mitochondrial and chloroplast electron transport systems? 3. Do electron transport chains create a gradient so that ATP synthase can generate ATP molecules? 4. What is the optimal temperature at which ATP synthase chemically converts ADP and a phosphate group into one molecule of ATP?

3. Do electron transport chains create a gradient so that ATP synthase can generate ATP molecules?

which bonds are created during the formation of the primary structure of a protein? 1. Phosphodiester bonds 2. disulfide bonds 3.peptide bonds 4.Hydrogen bonds

3. Peptide bonds

One of the primary functions of RNA molecules is to.. 1.transmit genetic information to offspring 2. act as a pattern or blue print to form DNA. 3. a function in the synthesis of proteins 4. make a copy of itself, thus ensuring genetic continuity.

3. a function in the synthesis of proteins

What biomolecules stores energy and is an important part of the cell membrane? 1.carbohydrates 2.nucleic acids 3. lipids 4.amino acids

3. lipids

All of the following cell components are found in a prokaryotic cell EXCEPT: 1. Cell membrane 2. enzymes 3. nuclear envelope 4. DNA 5.Ribosomes

3. nuclear envelope

Carbon dioxide most likely enters a cell through which of the following processes? 1. Active transport through aquaporins 2. facilitated diffusion 3. simple diffusion 4. Active transport through membrane proteins

3. simple diffusion

The cycle cycle "checkpoint" would be best described as: 1. any step where the cell cycle is blocked by a mutated protein 2. a site in the cytoplasm where proteins are inspected for mutations 3. specific stages where further progress of the cell cycle can be halted 4. either G1, S, G2, prophase, metaphase, anaphase or telophase

3. specific stages where further progress of the cell cycle can be halted

A transmembrane protein channel that opens or closes in response to a particular stimulus. 1. passive transport 2. Ion Channel 3. Gated Channel 4. Aquaporin

3.Gated Channel

Which of the following best supports the statement that mitochondria are descendants of endosymbiotic bacteria-like cells? 1.Neither mitochondria nor bacteria possess chloroplasts. 2.Glycolysis occurs in both mitochondria and bacteria. 3.Mitochondria and bacteria possess similar ribosomes and DNA. 4.Mitochondria and bacteria possess similar nuclei.

3.Mitochondria and bacteria possess similar ribosomes and DNA.

Which of the following components of the cell membrane is responsible for active transport? 1.Cholesterol 2.Lipid 3.Protein 4.Phospholipid

3.Protein

The structural level of a protein least affected by a disruption in hydrogen bonding is the tertiary level 1. Tertiary level 2.quaternary level 3.primary level 4.secondary level

3.primary level

To test the hypothesis that a particular plant synthesizes storage lipids by using glyceraldehyde 3-phosphate (G3P) from photosynthesis, a researcher plans to use radiolabeled precursors to track the molecules through the biosynthetic pathway. Which of the following radiolabeled precursors is most appropriate for the researcher to use? 1. 32P-labeled phosphate, because lipids are stored in plants as phospholipids 2. 35S-labeled methionine, because amino acids are incorporated into lipids during photosynthesis 3. 15N-labeled N2, because atmospheric nitrogen is fixed to amino acids by photosynthesis 4. 14C-labeled CO2, because atmospheric carbon is fixed to carbohydrates by photosynthesis

4. 14C-labeled CO2, because atmospheric carbon is fixed to carbohydrates by photosynthesis

Alcohol dehydrogenase (ADH) is an enzyme that aids in the decomposition of ethyl alcohol into nontoxic substances. Methyl alcohol acts as a competitive inhibitor of ethyl alcohol by competing for the same active site on ADH. When attached to ADH, methyl alcohol is converted to formaldehyde, which is toxic in the body. Which of the following statements best predicts the effect of increasing the concentration of substrate (ethyl alcohol), while keeping the concentration of the inhibitor (methyl alcohol) constant? 1.Competitive inhibition will be terminated because ethyl alcohol will bind to methyl alcohol and decrease ADH activity 2. There will be an increase in formaldehyde because ADH activity increasesADHactivity increases. 3. The peptide bonds in the active site of the enzyme will be denatured, inhibiting the enzyme. 4. Competitive inhibition will decrease because the proportion of the active sites occupied by substrate will increase.

4. Competitive inhibition will decrease because the proportion of the active sites occupied by substrate will increase.

The chemical reaction for photosynthesis is 6 CO2 + 12 H2O + light energy → C6H12O6 + 6 O2 + 6 H2O If the input water is labeled with a radioactive isotope of oxygen, 18O, then the oxygen gas released as the reaction proceeds is also labeled with 18O. Which of the following is the most likely explanation? 1. During the Calvin cycle, water is split, regenerating NADPH from NADP+, and oxygen gas is released. 2. During the light reactions of photosynthesis, water is split, the hydrogen atoms combine with the CO2, and oxygen gas is released. 3. During the Calvin cycle, water is split, the hydrogen atoms are added to intermediates of sugar synthesis, and oxygen gas is released. 4. During the light reactions of photosynthesis, water is split, removing electrons and protons, and oxygen gas is released.

4. During the light reactions of photosynthesis, water is split, removing electrons and protons, and oxygen gas is released.

Ethylene is an organic compound produced by ripening fruits. In a controlled experimnt, reserachers found that theylene gas stimulated the ripening process in newly harvested fruits. Which of the following describes the most likely connection between natual ethylene production and fruit ripening? 1. As a result of metabolic inactivity, newly harvested fruits are unable to absorb ethylene gas from the atmosphere. 2. Becasue of normal phenotypic variation, only some of the fruits in a given generation are expected to produce ethylene gas. 3. The rate of ethylene gas production by ripening fruits is an indicator of the relative age of an ecosystem. 4. Ethylene gas is a chemcial signal through which ripening fruits trigger the ripening process in other fruits.

4. Ethylene gas is a chemcial signal through which ripening fruits trigger the ripening process in other fruits.

All of the following are classes of carbohydrates except 1. Monosaccharides 2. Disaccharides 3. Polysaccharides 4. Glycerol

4. Glycerol

The epinephrine signaling pathway plays a role in regulatingglucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the best-2 adrenergic recpetor. A simplified model of the epinephrine signaling pathway represented below: A researcher claims that the epinephrine signaling pathway controls a catabolic process in muscle cells. Which of the following statements best helps justify the reseracher's claim? 1. Phophorylase kinase catalyzes the hydrolysis of ATP 2. The G protein in the epinephrine signaling pathway consists of three different subunits 3. Epinephrine is a signaling molecule that binds to a transmembrane protein 4. Glycogen phosphorylase catalyzes the conversion of glycogen to glucoses-1-phospate.

4. Glycogen phosphorylase catalyzes the conversion of glycogen to glucoses-1-phospate.

A researcher examining a root tip observes a plant cell with condensed sister chromatids, kinetochores with attached microtubles, and individual chromosomes that are aligned at the equatorial plate of the cell. Which of the following best describes what the next process will be in the cell? 1. The chromatin will decondense and the daughter cell will enter interphase 2. The nuclear envelope will break down and the spindle will begin to form 3. Homologous chromosomes (each with two sister chromatids) will movve toward opposite poles of the cell 4. Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell.

4. Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell.

Most cells that have transformed into cancer cells have which of the following characteristics when compared to normal, healthy cells? 1. Higher rates of protein translation 2. More carefully regulated rates of cell division 3. Lower rates of mitosis 4. Shorter cell cycles

4. Shorter cell cycles

A researcher proposes a model of an enzyme-catalyzed reaction in which a reactant is converted to a product. The model is based on the idea that the reactant passes through a transition state within the enzyme-substrate complex before the reactant is converted to the product. Which of the following statements best helps explain how the enzyme speeds up the reaction? 1. The enzyme's active site binds to and stabilizes the reactant, which decreases the free-energy change of the reaction. 2. The enzymes's active site binds to and stabilizes the product, which increases the amount of energy released by the reaction. 3. The enzyme's active site binds to and stabilizes both the reactant and the product at the same time, which increases the reaction's equilibrium constant. 4. The enzyme's active site bind to and stabilizes the transition state, which decreases the activation energy of the reaction.

4. The enzyme's active site bind to and stabilizes the transition state, which decreases the activation energy of the reaction.

The ability of a solution surrounding a cell to cause that cell to gain or lose water Incorrect answer: 1. Osmosis 2. Isotonic 3. Osmoregulation 4. Tonicity

4. Tonicity

If cells are grown in a medium containing radioactive Nitrogen, which of these molecules will be labeled? 1. both fatty acids and proteins 2. proteins only 3. nucleic acids only 4. both proteins and nucleic acids

4. both proteins and nucleic acids

Which of the following categories include all the others in the list? 1.polysaccharide 2.starch 3. disaccharide 4. carbohydrate

4. carbohydrate

The carbon that makes up organic molecules in plants is derived directly from: 1. combustion of fuels 2. carbon in the lithosphere. 3. carbon dioxide produced in respiration, 4. carbon fixed in photosynthesis

4. carbon fixed in photosynthesis

The tertiary structure of a polypeptide is the..... 1.Localized region of a polypeptide chain that forms an alpha helix or beta helix pleated sheet. 2.linear sequence of amino acids in a polypepide 3.overall three-dimensional shape of a protein composed of more than one polypeptide 4.overall three-dimensional shape of fully folder peptide

4..overall three-dimensional shape of fully folder peptide

Carbohydrate-synthesizing reactions of photosynthesis directly require 1.chlorophyll and CO2 2.products of the light reactions 3. darkness 4.O2 and H2O

4.O2 and H2O