APBIO Final

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?

(A) The enzyme’s active site binds to and stabilizes the reactant, which decreases the free-energy change of the reaction.

(B) The enzyme’s active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction.

(C) The enzyme’s active site binds to and stabilizes the product, which increases the amount of energy released by the reaction.

(D) 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.

(B) The enzyme’s active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction.

The protein is made up of amino acids linked together in a chain. Some humans produce a version the CFTR of the protein in which phenylalanine (an amino acid) has been deleted from position 508 of the amino acid chain. Which of the following best predicts how the amino acid deletion will affect the structure of the protein?

(A) It will have no observable effect on the structure of the protein.

(B) It will affect the primary structure of the protein, but the other levels of protein structure will not be affected.

(C) It will affect the secondary and tertiary structures of the protein, but the primary structure will not be affected.

(D) It will affect the primary, secondary, and tertiary structures of the protein.

(D) It will affect the primary, secondary, and tertiary structures of the protein.

Amylase is an enzyme that converts carbohydrate polymers into monomers. Glycogen synthase is one of the enzymes involved in converting carbohydrate monomers into polymers.

Which of the following best explains the reactions of these enzymes?

(A) Amylase aids in the removal of a water molecule to break covalent bonds whereas glycogen synthase aids in the addition of a water molecule to form covalent bonds.

(B) Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen synthase aids in the removal of a water molecule to form covalent bonds.

(C) Amylase aids in the addition of a water molecule to form covalent bonds whereas glycogen synthase aids in the removal of a water molecule to break covalent bonds.

(D) Amylase aids in the removal of a water molecule to form covalent bonds whereas glycogen synthase aids in the addition of a water molecule to break covalent bonds.

(B) Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen synthase aids in the removal of a water molecule to form covalent bonds.

Which of the following statements best helps explain the reaction specificity of an enzyme?

(A) The free energy of the reactants is greater than the free energy of the products.

(B) The equilibrium constant of the reaction is much greater than 1.

(C) The shape and charge of the substrates are compatible with the active site of the enzyme.

(D) The concentration of the enzyme inside living cells is greater than the concentration of substrate.

(C) The shape and charge of the substrates are compatible with the active site of the enzyme.

Which of the following best describes the hydrolysis of carbohydrates?

(A) The removal of a water molecule breaks a covalent bond between sugar monomers.

(B) The removal of a water molecule forms a covalent bond between sugar monomers.

(C) The addition of a water molecule breaks a covalent bond between sugar monomers.

(D) The addition of a water molecule forms a covalent bond between sugar monomers.

(C) The addition of a water molecule breaks a covalent bond between sugar monomers.

Humans produce sweat as a cooling mechanism to maintain a stable internal temperature. Which of the following best explains how the properties of water contribute to this physiological process?

(A) The high specific heat capacity of water allows the body to absorb a large amount of excess heat energy.

(B) The high heat of vaporization of water allows the body to remove excess heat through a phase change of water from liquid to gas.

(C) The high surface tension of water contributes to the physical process by which water leaves the body.

(D) The high melting temperature of water allows the body to remove excess heat through a phase change of water from solid to liquid.

(B) The high heat of vaporization of water allows the body to remove excess heat through a phase change of water from liquid to gas.

Which of the following best describes how amino acids affect the tertiary structure of a protein?

(A) The number of amino acids determines the tertiary structure of the protein.

(B) The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein.

(C) The R-group of the last amino acid that is added to a growing polypeptide chain determines the next amino acid that is added to the chain.

(D) The sequence of the amino acids in the polypeptide chain determines the protein’s primary structure but has no effect on its tertiary structure.

(B) The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein.

Pyruvate kinase, a key enzyme in the glycolysis pathway, is inhibited by the amino acid alanine. The ability of alanine to inhibit the enzyme is not affected by increasing the concentration of substrate.

Which of the following best explains the mechanism by which alanine inhibits pyruvate kinase activity?

(A) Alanine binds to an allosteric site of the enzyme, changing the shape of the enzyme’s active site.

(B) Alanine increases the enzyme-substrate binding until the enzyme becomes saturated.

(C) Alanine is a competitive inhibitor that reversibly binds to the active site of the enzyme.

(D) Alanine binds to the substrate, preventing the substrate from being able to bind to the active site of the enzyme.

(A) Alanine binds to an allosteric site of the enzyme, changing the shape of the enzyme’s active site.

A researcher claims that increased atmospheric carbon dioxide levels cause increased growth rates in plants.

Which of the following statements best supports the researcher’s claim?

(A) Atmospheric carbon dioxide is produced by the burning of fossil fuels, which are formed from the remains of living organisms such as plants.

(B) Atmospheric carbon dioxide is a byproduct of cellular respiration, which is a metabolic process that occurs in plants and other living organisms.

(C) Atmospheric carbon dioxide typically enters plant leaves through stomata, which plants rely on for regulating gas exchange with the atmosphere.

(D) Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.

(D) Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.

Which of the following best describes the process by which the bacteria are breaking down the glucose to produce lactic acid?

(A) The bacteria are breaking down sugars in the absence of oxygen.

(B) The bacteria are creating a gradient to synthesize more .

(C) The bacteria are using their mitochondria to break down glucose in the presence of oxygen.

(D) The bacteria are producing in the Krebs cycle that is then converted into lactic acid.

(A) The bacteria are breaking down sugars in the absence of oxygen.

In an experiment, a scientist isolates mitochondria from living cells and suspends them in two different buffered solutions. One solution is maintained at pH 4, while the other solution is maintained at pH 9. The scientist finds that mitochondria in the solution at pH 4 continue to produce ATP but those in the pH 9 solution do not.

The results of the experiment can be used as evidence in support of which of the following scientific claims about mitochondrial activity?

(A) Mitochondria in a cell-free environment are unable to convert thermal energy into ATP.

(B) The electron transport chain pumps electrons from the cytosol to the mitochondrial matrix.

(C) ATP production in mitochondria requires a hydrogen ion gradient that favors movement of protons into the mitochondrial matrix.

(D) ATP synthase molecules change their orientation in relation to the proton gradient across the

(C) ATP production in mitochondria requires a hydrogen ion gradient that favors movement of protons into the mitochondrial matrix.

Which of the following describes a metabolic consequence of a shortage of oxygen in muscle cells?

(A) An increase in blood pH due to the accumulation of lactic acid

(B) No ATP production due to the absence of substrate-level phosphorylation

(C) A buildup of lactic acid in the muscle tissue due to fermentation

(D) A decrease in the oxidation of fatty acids due to a shortage of ATP

(C) A buildup of lactic acid in the muscle tissue due to fermentation

A scientist claims that Elysia chlorotica, a species of sea slug, is capable of photosynthesis.

Which of the following observations provides the best evidence to support the claim?

(A) Elysia chlorotica will die if not exposed to light.

(B) Elysia chlorotica grows when exposed to light in the absence of other food sources.

(C) Elysia chlorotica grows faster when exposed to light than when placed in the dark.

(D) Elysia chlorotica grows in the dark when food sources are available.

(B) Elysia chlorotica grows when exposed to light in the absence of other food sources.

Which of the following best describes the role of and in the process of photosynthesis?

(A) ATP is required for the chemiosmotic production of during photosynthesis.

(B) ATP and NADPH are necessary to initiate the Krebs cycle in photosynthesis.

(C) ATP and NADPH are carriers of chemical energy that is used in the production of carbohydrates.

(D) ATP and NADPH are required to boost electrons to a higher energy state in photosystems and .

(C) ATP and NADPH are carriers of chemical energy that is used in the production of carbohydrates.

A researcher is investigating the effects of a chemical that makes thylakoid membranes permeable to hydrogen ions (H+). Which of the following is the most likely direct effect of adding the chemical to plant cells?

(A) The plant cells will produce less .

(B) The chloroplasts will generate less .

(C) Chlorophyll will require less light energy to excite its electrons.

(D) The plant cells will split fewer water molecules into hydrogen ions and oxygen.

(B) The chloroplasts will generate less .

Which of the following best describes the role of water in photosynthesis?

(A) Water is the only source of protons for the formation of a proton gradient.

(B) Water molecules donate electrons to the electron transport chain.

(C) Water molecules combine with stored carbon molecules to produce glucose.

(D) Water is the terminal electron acceptor for electrons that pass through the electron transport chain.

(B) Water molecules donate electrons to the electron transport chain.

A researcher claims that the synthesis of from and inorganic phosphate is essential to cellular function.

Which of the following statements best helps justify the researcher’s claim?

(A) ATP is a small molecule that some cells release into their environment as a way of communicating with other cells.

(B) ATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy.

(C) Inorganic phosphate is a substance that cells typically acquire from their environment.

(D) synthase is a mitochondrial enzyme that catalyzes the conversion of and to .

(B) ATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy.

Which of the following processes is most likely to occur as a result of an animal cell receiving a signal to initiate apoptosis?

(A) Ribosomes will translate mRNA to produce proteins.

(B) Vesicles will release extracellular growth factors via exocytosis.

(C) Lysosomes will release digestive enzymes into the cytosol.

(D) Vacuoles will fuse with the cellular membrane.

(C) Lysosomes will release digestive enzymes into the cytosol.

A scientist designed an experiment to test an artificial membrane that mimics the phospholipid bilayer of a cell. The scientist built a tube that was divided by an artificial membrane and filled with distilled water. The scientist put a known amount of a protein into the water on one side of the membrane. After some time, the scientist measured the concentration of the protein on either side of the membrane but found that there had been no change.

6. Which of the following experimental changes would allow the scientist to observe transport of a solute across the artificial membrane?

(A) Increase the solute concentration in the solution

(B) Use a small, nonpolar solute instead of a protein

(C) Increase the temperature of the solution

(D) Add artificial aquaporins to the membrane

(B) Use a small, nonpolar solute instead of a protein

Which of the following describes the most likely location of cholesterol in an animal cell?

(A) Embedded in the plasma membrane

(B) Dissolved in the cytosol

(C) Suspended in the stroma of the chloroplast

(D) Bound to free ribosomes

(A) Embedded in the plasma membrane

Which of the following statements best supports the claim that certain organelles within eukaryotic cells evolved from free-living prokaryotic cells?

(A) The cytoplasm of both eukaryotes and prokaryotes is surrounded by a plasma membrane.

(B) Eukaryotes and prokaryotes both contain ribosomes, but the ribosomes of eukaryotes are more complex in structure than those of prokaryotes.

(C) Eukaryotes exchange segments of internal membranes between the endoplasmic reticulum and Golgi apparatus, but prokaryotes have no such internal membranes.

(D) Some organelles contain their own that is more similar to prokaryotic in structure and function than to the eukaryotic found in the cell's nucleus.

(D) Some organelles contain their own that is more similar to prokaryotic in structure and function than to the eukaryotic found in the cell's nucleus.

13. Which of the following is evidence that eukaryotes and prokaryotes share a common ancestor?

(A) All eukaryotes and prokaryotes contain linear .

(B) All eukaryotes and prokaryotes contain ribosomes.

(C) All eukaryotes and prokaryotes use organic molecules as an energy source.

(D) All eukaryotes and prokaryotes are capable of mitosis.

(B) All eukaryotes and prokaryotes contain ribosomes.

Which of the following best explains how the phospholipid bilayer of a transport vesicle contributes to cellular functions?

(A) The phospholipid bilayer allows the vesicle to fuse with the Golgi apparatus and the plasma membrane, allowing the exocytosis of proteins.

(B) The phospholipid bilayer physically connects the nuclear envelope to the rough endoplasmic reticulum, thus increasing the rate of transcription and translation.

(C) The phospholipid bilayer of a transport vesicle contains chemicals that digest the proteins made in the rough endoplasmic reticulum.

(D) The phospholipid bilayer contains enzymes that catalyze the conversion of hydrogen peroxide to water and oxygen.

(A) The phospholipid bilayer allows the vesicle to fuse with the Golgi apparatus and the plasma membrane, allowing the exocytosis of proteins.

All eukaryotic cells contain at least one Golgi complex, typically located in the cytoplasm and near the endoplasmic reticulum.

Which of the following best describes a process that occurs within the Golgi complex?

(A) Enzymatic modification of newly synthesized integral membrane proteins

(B) Synthesis of cytosolic proteins based on the nucleotide sequences of

(C) Degradation of proteins by hydrolytic enzymes contained within the complex

(D) Synthesis of various types of lipidsAll eukaryotic cells contain at least one Golgi complex, typically located in the cytoplasm and near the endoplasmic reticulum.

(A) Enzymatic modification of newly synthesized integral membrane proteins

Which of the following claims is scientifically accurate and consistent with an observation that a decrease in lysosome production within a cell leads to a decline in mitochondrial activity?

(A) A lack of lysosomes will cause a decrease in the synthesis of enzymes necessary for cellular respiration.

(B) Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration.

(C) Fewer lysosomes will be available to store materials required for the functioning of the mitochondria.

(D) Lysosomes will not be available to modify proteins so that they are targeted to the mitochondria.

(B) Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration.

The endosymbiont theory proposes a model for the evolution of mitochondria. According to the model, an ancestral eukaryote engulfed a small, free-living prokaryotic organism. The engulfed prokaryote then formed an endosymbiotic relationship with the eukaryotic host.

Which of the following observations best supports the model?

(A) Prokaryotes and eukaryotes acquire nutrients from the surrounding environment.

(B) Organelles such as mitochondria and the endoplasmic reticulum have membranes composed of phospholipids.

(C) Mitochondria and some prokaryotes share similar metabolic reactions that produce .

(D) Eukaryotes evolved after prokaryotes and have more complex structures.

(C) Mitochondria and some prokaryotes share similar metabolic reactions that produce.

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 inside the cell. The cyclic binds to and activates cytosolic enzymes that then activate other enzymes in the cell.

Which of the following statements best describes the role of cyclic in the signal transduction pathway?

(A) It acts as a signaling molecule that passes the signal from the cell to other cells.

(B) It acts as a receptor that carries the signal from outside the cell to inside the cell.

(C) It acts as a second messenger that helps relay and amplify the signal within the cell.

(D) It acts as a channel protein that transmits the signal across the cell’s nuclear membrane.

(C) It acts as a second messenger that helps relay and amplify the signal within the cell.