Class MCQs

What is the function of 2,3-BPG? a) Binds to the allosteric site of hemoglobin, thus increasing efficiency of hemoglobin b) Reduces the blood pH c) Disallows for oxygen to bind back to hemoglobin d) Binds to CO2 e) None of the above

A and C

Which two amino acids obstruct alpha-helix formation (G of each AA's propensity towards the helix structure is given) a) Gly (4.6) b) Ala (0) c) Met (0.9) d) Pro (5) e) His (2.6) f) Asp (2.5)

A and D

A _________ competes with substrates to bind to an enzymes active site a.) competitive inhibitor b.) noncompetitive inhibitor c.) uncompetitive inhibition d.) both A and B e.) none of the above

A

Which of the following is not true about secondary protein structure? A) The hydrophilic/hydrophobic character of amino acid residues is important to secondary structure. B) The ability of peptide bonds to form intramolecular hydrogen bonds is important to secondary structure. C) The alpha helix, beta pleated sheet and beta turns are examples of protein secondary structure. D) The steric influence of amino acid residues is important to secondary structure.

A

Which of the following is true of amino acids? (Select all that apply). A) In physiological conditions they exist in the L conformation. B) They are all hydrophobic. C) There are only 20. D) They cannot be modified. E) They are the monomeric units of sugars.

A

Which of the following are examples of Van der Waals interactions? a.) dipole-dipole forces b.) London Dispersion forces c.) ionic bonding d.) none of the above

A and B

Enzyme interaction with the transition state does which of the following? (Select all that apply). A) Decrease the activation energy. B) Increases the free energy (G) of the reactants. C) Decreases the free energy (G) of the products D) Increases the free energy (G) of the products.

A only

Which of the following is/are true about acid/base catalysis? a. One species is oxidized or loses electrons b. One species is reduced or gains electrons c. The activation energy is lowered d. Electrons are transferred by cofactors or coenzymes e. All of the above f. None of the above

A, B, D

Which of the follow is/are true regarding hemoglobin? a) Adult hemoglobin binds to BPG, resulting in a lower affinity for oxygen. b) Adult hemoglobin consists of 2 alpha subunits and 2 beta subunits. c) Fetal hemoglobin binds to BPG resulting in a higher affinity for oxygen. d) Sickle cell anemia results from the aggregation of hemoglobin molecules with abnormal delta subunits. e) Hemoglobin exists in a T and R state.

A, B, E

Which of the following is true about Km? A. It is the substrate concentration where velocity is ½ of Vmax. B. A low Km indicates that the enzyme only needs a small amount of substrate to become saturated. C. A high Km indicates that the enzyme needs a small amount of substrate to become saturated. D. It is the Michaelis constant.

A,B, and D

A protein's primary structure: A. Is a three-dimensional folding structure of a polypeptide. B. Is a sequence of amino acids in a polypeptide chain. C. Is attributed to the interactions between the amino acids' R groups. D. Contains disulfide bonds that firmly holds the polypeptide together.

B

BPG is a _______ modification and induces _________ cooperativity. Choose the correct pair to complete the statement. A) Allosteric, positive B) Allosteric, negative C) Competitive, positive D) Competitive, negative

B

Which of the following statements of Induced Fit are false? A) The active site undergoes a change in structure B) Suppresses catalysis, as the enzyme converts substrate to product C) This theory opposes the lock and key theory D) Enhances catalysis, as the enzyme converts substrate to product.

B

Which procedure is used in the degradation of proteins from the amino terminus, in order to understand the proteins original structure? A. protein dissolving B. edman degradation C. size-exclusion chromatography D. electrophoresis

B

Which characteristics are NOT true of the induced fit model? a. Molecular conformational modification b. Protein-ligand conformation reduces binding site fit to a molecule c. Protein-ligand interactions affect other conformational changes d. Enzyme-substrate binding can't be regulated by other ligand interactions

B and D

Which of the following traits of non-competitive inhibitors is TRUE?(choose all that apply) A. They bind to the active site of the enzyme B. Adding more substrate will NOT increase the chances of the enzyme binding to the substrate C. They induce a conformational change D. They bind to the allosteric site of the substrate E. Km is decreased F. none of the above

B, C, D

How does myoglobin differ from hemoglobin a. Only hemoglobin is an oxygen binding protein b. Myoglobin and hemoglobin have different affinities for oxygen c. Myoglobin and hemoglobin have different structural makeups d. In its deoxygenated state, hemoglobin has a higher affinity for oxygen compared to myoglobin e. Myoglobin is found in muscle tissue and hemoglobin is found in red blood cells f. Myoglobin transports oxygen and hemoglobin transports carbon dioxide

B, C, and E

A protease is an enzyme that breaks down what? A) Amino Acids B) Carbohydrates C)Proteins D)Lipids

C

Consider the twenty amino acids. _______ is not optically active, because of its ________ side chain. A) Lysine, basic B) Lysine, nitrogen containing C) Glycine, hydrogen atom D) Glycine, unbranched

C

How many amino acids are there in one turn of an α helix? a) 2 b) 5.3 c) 3.6 d) 10.1 e) 4.2

C

Why are biological buffers important? a) Because they provide nutrients to the body b) Allow for appropriate gas exchange c) Releases or binds to H+ in order to maintain a stable pH d) All of the above e) None of the above

C

The term Kd represents the following when talking about ligand kinetics? a) the ligand's association constants b) the fraction of occupied sites c) the ligands dissociation constant d) the equilibrium of ligand and protein constant e) the concentration of ligand at which half of all protein binding sites are occupied.

C and E

What is true about Vmax? A. The rate of a reaction observed at which the substrate is present in excess B. The rate of a reaction observed at which the enzyme can be saturated. C. The substrate concentration at which the enzyme works at 1/2 is velocity D. A & B E. None of the above

D

Which of the following appropriately describes the MWC (concerted) model? a.) All subunits are functionally identical b.) Adjacent subunits respond to ligand-binding c.) Ligand-binding shifts the equilibrium of the proteins' state d.) A & C e.) B & C f.) All of the above

D

What is a protein's secondary structure? a.) Arrangement of the protein subunits with respect to one another. b.) Three-dimensional form of local segments of proteins. c.) Alpha helixes and Beta sheets. d.) An amino acid sequence in a polypeptide chain. e.) b & c f.) None of the above.

E

Which conditions will result in an increase in oxygen binding to hemoglobin? a. Increase in [H+] b. Increase in [O2] c. Decrease in [H+] d.) A & C e.) B & C f.) None of the above

E

Which of the following are methods used for isolating/separating based on size? A. Ion-Exchange Chromatography B. SDS-PAGE C. Gel Filtration D. A&B E. B&C F. None of the Above

E

Which of the following are true of enzyme behavior? a) They alter the equilibrium constant (Keq) b) They increase the reaction rate c) They are consumed during the reaction d) They are pH and temperature sensitive e) b and d

E

Which of the following is true regarding T-state and R-state of hemoglobin? a.) R-state becomes T-state when oxygen binds to the heme group. b.) T-state and R-state mean "tense" and "relaxed" states, respectively. c.) R-state has a lower affinity to oxygen. d.) T-state has a lower affinity to oxygen. e.) b & d f.) None of the above.

E

Which of the following about zwitterions are false? a. It is a dipolar ion b. Contains only positively charged functional groups c. Contains only negatively charged functional groups d. Amino acids are zwitterion molecules e. a & d f. b & c g. None of the above

F

Which of the following molecules could/can form micelles? a) Glycoproteins b) Phospholipids c) Detergents d) a & b e) a & c f) b& c g) all of the above

G

The "T" state refers to the __________ state where it has a __________ affinity for oxygen. A) Tense, Higher B) Timid, Higher C) Tense, Lower D) Timid, Lower

c

Which of the following statements about the competitive inhibition of an enzyme catalyzed reaction is correct? A) A competitive inhibitor and substrate can bind at the same time to the enzyme B) The Vmax and Km for a reaction are unchanged in the presence of a competitive inhibitor C) The Vmax for a reaction remains unchanged in the presence of a competitive inhibitor D) The Km for a reaction remains unchanged in the presence of a competitive inhibitor

c

An amphipathic molecule has both hydrophobic and hydrophilic regions. Which of the following molecules are amphipathic? a. Glycine b. Phosphatidylcholine c. Glycerol d. Phenylalanine e. b & d

e

Which of the following is/are true about collagen? a. It makes up about 25 to 35% of the total proteins in mammals b. It is comprised of about 30% Glycine c. It is found in connective tissue d. It is an insoluble protein e. None of the above f. All of the above

f