Question 1

Which of the following statements best describes the effect of a competitive inhibitor on enzyme kinetics?

Accepted Answer

It leaves $$V_{max}$$ unchanged and increases $$K_m.$$

Question 2

In a Lineweaver–Burk plot, which feature is characteristic of uncompetitive inhibition?

Accepted Answer

Lines are parallel with different y-intercepts.

Question 3

A patient is exposed to DFP (diisopropyl fluorophosphate), which irreversibly inhibits serine proteases. What is the molecular basis for this inhibition?

Accepted Answer

DFP covalently modifies Ser195, permanently inactivating the enzyme.

Question 4

During the catalytic mechanism of chymotrypsin, which residue acts as both an acid and a base?

Accepted Answer

His57

Question 5

Which step in the chymotrypsin mechanism involves the formation of a tetrahedral intermediate?

Accepted Answer

Nucleophilic attack by Ser195 on the substrate carbonyl

Question 6

Which of the following equations correctly represents the initial velocity ($$V_0) $$for competitive inhibition?

Accepted Answer

$$V_0$$ = \frac{V_{max}[S]}{\alpha K_m + [S]}$$ where $$\alpha = 1 + \frac{[I]}{K_I}$$

Question 7

Which lipid class is characterized by the absence of a glycerol backbone and is built on sphingosine?

Accepted Answer

Sphingolipids

Question 8

What is the primary function of flippases in membrane dynamics?

Accepted Answer

Catalyze translocation of phosphatidylethanolamine and phosphatidylserine from extracellular to cytoplasmic leaflet

Question 9

Which of the following statements about cholesterol is TRUE?

Accepted Answer

It contains a polar head group and a nonpolar hydrocarbon body.

Question 10

A mutation in the gene encoding GLUT1 results in impaired glucose transport in erythrocytes. Which kinetic equation best describes GLUT1-mediated glucose uptake?

Accepted Answer

$$V_0$$ = \frac{V_{max}[S]_{out}}{K_t + [S]_{out}}$$

Question 11

Which enzyme is responsible for removing sugar units stepwise from gangliosides during lysosomal degradation?

Accepted Answer

Lysosomal enzymes

Question 12

Which type of enzyme inhibition is characterized by the inhibitor binding only to the enzyme–substrate (ES) complex, resulting in parallel lines on a Lineweaver–Burk plot?

Accepted Answer

Uncompetitive inhibition

Question 13

Which of the following is a function of membrane proteins classified as 'receptors'?

Accepted Answer

Detect extracellular signals and trigger molecular changes inside the cell

Question 14

Which of the following statements about mixed inhibition is correct?

Accepted Answer

The inhibitor binds to both free enzyme and ES complex at a site distinct from the active site.

Question 15

Which of the following best explains the clinical significance of sphingolipids in human blood groups?

Accepted Answer

They determine blood groups by the oligosaccharide head groups of glycosphingolipids.

Question 16

Which of the following is TRUE regarding the effect of uncompetitive inhibition on enzyme kinetics?

Accepted Answer

$$V_{max}$$ and $$K_m$$ both decrease.

Question 17

Which step in the chymotrypsin mechanism is responsible for regenerating the enzyme for another catalytic cycle?

Accepted Answer

Deacylation by water activation and collapse of the second tetrahedral intermediate

Question 18

Which membrane protein is responsible for providing a hydrophilic transmembrane pathway for solute transport?

Accepted Answer

Transporters

Question 19

Which of the following statements about scramblases is correct?

Accepted Answer

They move any membrane phospholipid across the bilayer down its concentration gradient.

Enzyme Inhibition, Chymotrypsin Mechanism, Lipids, and Membrane Proteins: Structured Study Notes

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