Question 1

Which of the following best describes noncompetitive inhibition of an enzyme?

Accepted Answer

The inhibitor binds to a site other than the active site, causing a conformational change that reduces enzyme activity.

Question 2

A patient is found to have a deficiency in vitamin B1. Which coenzyme is most likely to be affected, and what is its primary function?

Accepted Answer

Thiamine pyrophosphate (TPP); decarboxylation reactions

Question 3

Which of the following statements about feedback inhibition in metabolic pathways is correct?

Accepted Answer

The end product of a pathway acts as an allosteric regulator of the first enzyme, often inhibiting its activity.

Question 4

Which vitamin is ingested in its provitamin form and is essential for vision and cell growth?

Accepted Answer

Vitamin A (retinol, from β-carotene)

Question 5

A competitive inhibitor will have which of the following effects on enzyme kinetics?

Accepted Answer

$$V_{max} is $$unchanged, $$K_m is $$increased.

Question 6

Which of the following best explains why fat-soluble vitamins can be toxic in high amounts?

Accepted Answer

They are stored in the liver and fatty tissues, leading to accumulation.

Question 7

Which of the following is a function of vitamin K in the human body?

Accepted Answer

Required for the synthesis of prothrombin, a key enzyme in blood clotting

Question 8

A patient presents with symptoms of scurvy, such as bleeding gums and poor wound healing. Which vitamin deficiency is most likely responsible, and what is its biochemical role?

Accepted Answer

Vitamin C; collagen synthesis and antioxidant

Question 9

Which of the following statements about coenzymes is correct?

Accepted Answer

Coenzymes are organic molecules, often derived from water-soluble vitamins, that assist enzymes in catalysis.

Question 10

Which of the following best describes the mechanism of irreversible enzyme inhibition?

Accepted Answer

The inhibitor forms a covalent bond with the enzyme, permanently inactivating it.

Question 11

Which of the following is a real-world example of covalent modification regulating enzyme activity?

Accepted Answer

Addition of a phosphate group to serine, threonine, or tyrosine residues to activate or deactivate an enzyme

Question 12

Which of the following best describes the function of zymogens in the body?

Accepted Answer

They are inactive enzyme precursors that require cleavage of a peptide segment to become active.

Question 13

A blood test reveals elevated levels of creatine kinase (CK) and lactate dehydrogenase (LDH). What is the most likely clinical interpretation?

Accepted Answer

The patient may have experienced a heart attack (myocardial infarction).

Question 14

Which of the following statements about water-soluble vitamins is correct?

Accepted Answer

They are not stored in the body and excess amounts are excreted in urine.

Question 15

Which of the following is the correct pair of vitamin and its coenzyme form involved in redox reactions?

Accepted Answer

Vitamin B2 (riboflavin); FAD/FMN

Question 16

Which of the following best describes the role of antibodies in a lateral flow COVID-19 test?

Accepted Answer

They are protective proteins that specifically bind to the viral spike protein.

Question 17

Which of the following statements about allosteric regulation is correct?

Accepted Answer

Allosteric regulators bind to a site other than the active site and can either increase or decrease enzyme activity.

Question 18

A patient is prescribed methotrexate, a drug that inhibits the conversion of folic acid to tetrahydrofolate. What is the most likely biochemical consequence?

Accepted Answer

Impaired synthesis of deoxyribonucleic acids (DNA)

Question 19

Which of the following best describes the effect of uncompetitive inhibition on enzyme kinetics?

Accepted Answer

$$V_{max}$$ and $$K_m$$ are both decreased by the same ratio.

Regulation of Enzyme Activity, Vitamins, and Diagnostic Enzyme Testing

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