Question 1

During cellular respiration, carbon dioxide is produced as a waste product. Which process is primarily responsible for this production?

Accepted Answer

Citric acid cycle (Krebs cycle)

Question 2

Which amino acid would most likely be found on the surface of a soluble protein in the cytoplasm?

Accepted Answer

Glutamate

Question 3

A mutation replaces a negatively charged amino acid on the surface of hemoglobin with a nonpolar amino acid. What is the most likely effect?

Accepted Answer

Decreased solubility and increased aggregation

Question 4

Which statement about $$eta-$$sheet structures in proteins is correct?

Accepted Answer

Hydrogen bonds form between backbone atoms of adjacent strands.

Question 5

The peptide bond in proteins is planar because:

Accepted Answer

It has partial double-bond character due to resonance.

Question 6

Which of the following interactions is most important in stabilizing tertiary structure in proteins?

Accepted Answer

Disulfide bonding

Question 7

What is the net charge on the tripeptide glutathione (Glu-Cys-Gly) at physiological pH ($$pH = 7.4$$)?

Accepted Answer

$$-2$$

Question 8

You discover a new protein that has a highly repetitive sequence and forms strong, insoluble fibers. Which type of protein is this most likely to be?

Accepted Answer

Fibrous structural protein

Question 9

Which statement correctly describes the role of the proximal histidine in hemoglobin?

Accepted Answer

It coordinates the heme iron, linking the heme to the protein.

Question 10

A newly-identified protein is found to contain a significant number of histidine residues at its active site. What is the most likely function of these residues?

Accepted Answer

Acid-base catalysis

Question 11

For a reaction that can take place with or without a catalyst, what effect does the catalyst have on the activation energy ($$E_a) $$and the equilibrium constant ($$K_{eq}$$)?

Accepted Answer

$$E_a$$ decreases, $$K_{eq} no $$change

Question 12

Which of the following is the main role of molecular chaperones in the cell?

Accepted Answer

Prevent protein misfolding and aggregation

Question 13

Chymotrypsin catalyzes peptide bond hydrolysis by acting as a general base. What is the role of Asp 32 in this mechanism?

Accepted Answer

Asp 32 deprotonates water, activating it for nucleophilic attack.

Question 14

Which of the following catalytic strategies is used by enzymes to lower the activation energy of a reaction?

Accepted Answer

Acid-base catalysis

Question 15

In the reaction coordinate diagram for an enzyme-catalyzed reaction, what does a lower peak in the curve represent?

Accepted Answer

Lower activation energy ($$E_a)$$

Question 16

Which effector stabilizes the T-state of hemoglobin, decreasing oxygen affinity?

Accepted Answer

BPG (2,3-bisphosphoglycerate)

Question 17

What type of secondary structure is indicated by a right-handed coil with 3.6 residues per turn and a pitch of 5.4 Å?

Accepted Answer

$$\alpha-$$helix

Question 18

Which bond is formed between two cysteine residues in a protein, contributing to tertiary structure stability?

Accepted Answer

Disulfide bond

Question 19

A mutation in hemoglobin causes a hydrophobic amino acid to be exposed on the surface. What is the most likely clinical consequence?

Accepted Answer

Sickle cell disease due to protein aggregation

Question 20

Which of the following best describes the Bohr effect in hemoglobin?

Accepted Answer

Oxygen binding decreases as pH decreases.

Biochemistry Study Notes: Protein Structure, Function, and Enzyme Catalysis EXAM 2

Guida di studio - Domande di pratica

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