APBIO Chemistry Test

Reivew for finals!

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.