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 inhibitor of the first enzyme, decreasing its activity.

Question 4

Which vitamin is required for the synthesis of prothrombin and is essential for blood clotting?

Accepted Answer

Vitamin K (phylloquinone)

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 correct pairing of vitamin, coenzyme, and function?

Accepted Answer

Vitamin B2 (riboflavin); FAD; electron transfer

Question 8

Which of the following statements about zymogens is true?

Accepted Answer

Zymogens are inactive enzyme precursors that require removal of a peptide segment to become active.

Question 9

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

Question 10

Which of the following best describes the role of coenzymes in enzyme-catalyzed reactions?

Accepted Answer

Coenzymes are organic molecules, often derived from vitamins, that participate in catalysis by carrying chemical groups or electrons.

Question 11

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

Accepted Answer

They are primarily hydrophilic and often function as coenzymes.

Question 12

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 13

Which of the following statements about allosteric regulation is correct?

Accepted Answer

Allosteric regulation involves binding of a molecule at a site other than the active site, which can increase or decrease enzyme activity.

Question 14

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

Accepted Answer

Vitamin A (\beta-carotene/retinol)

Question 15

Which of the following best describes irreversible enzyme inhibition?

Accepted Answer

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

Question 16

Which of the following is a correct statement about the effect of uncompetitive inhibition on enzyme kinetics?

Accepted Answer

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

Question 17

The lateral flow assay used in COVID-19 rapid tests relies on which class of proteins to detect the presence of viral antigens?

Accepted Answer

Antibodies (protective proteins)

Question 18

Which of the following best describes the function of Vitamin D in the human body?

Accepted Answer

It increases absorption of calcium and phosphate in the gut and retention in the kidneys.

Question 19

Which of the following is a true statement about the relationship between $$K_m$$ and enzyme affinity for substrate?

Accepted Answer

A lower $$K_m$$ indicates a higher affinity for the substrate.

Regulation, Vitamins, and Diagnostic Enzyme Function in Biochemistry

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