Question 1

Which of the following best explains why substrate concentration in cells is often close to $K_m$ for their respective enzymes?

Accepted Answer

It allows enzyme activity to fluctuate efficiently with changes in substrate concentration.

Question 2

What does a high elasticity coefficient indicate about an enzyme in a metabolic pathway?

Accepted Answer

The enzyme's activity changes significantly with small changes in substrate concentration.

Question 3

Which of the following statements about AMP-activated protein kinase (AMPK) is correct?

Accepted Answer

AMPK activation favors catabolic pathways that generate ATP.

Question 4

Why are enzymes at metabolic pathway branch points generally regulated?

Accepted Answer

They control the flux of metabolites into different pathways, affecting overall metabolism.

Question 5

Which enzyme is considered the most influential in regulating the rate of glycolysis?

Accepted Answer

Phosphofructokinase-1 (PFK-1)

Question 6

Given the Michaelis-Menten equation $v = \frac{V_{max}[S]}{K_m + [S]}$, what happens to the reaction velocity $v$ when $[S] \gg K_m$?

Accepted Answer

The reaction velocity becomes independent of substrate concentration and approaches $V_{max}$.

Question 7

Why does glucokinase have a much higher $K_m$ for glucose than hexokinase?

Accepted Answer

Glucokinase is designed to function only when glucose levels are high, such as after a meal.

Question 8

A patient with a mutation that decreases the $K_m$ of hexokinase for glucose would most likely experience which of the following?

Accepted Answer

Increased glycolytic flux even at low glucose concentrations.

Question 9

Which of the following best describes the difference in the kinetic curves of hexokinase and glucokinase as shown in the provided graph?

Accepted Answer

Hexokinase reaches $V_{max}$ at lower glucose concentrations than glucokinase.

Question 10

In the context of metabolic regulation, what is the primary role of feedback inhibition?

Accepted Answer

To prevent the accumulation of intermediates and end products.

Question 11

If a cell's ATP concentration is high, what is the expected effect on glycolysis?

Accepted Answer

Glycolysis is inhibited due to allosteric regulation by ATP.

Question 12

Which of the following scenarios best illustrates the concept of metabolic flux control?

Accepted Answer

A rate-limiting enzyme is regulated to adjust the flow of metabolites through a pathway.

Question 13

A researcher observes that an enzyme's activity increases sharply with a small increase in substrate concentration. What does this suggest about the enzyme's $K_m$ relative to the substrate concentration?

Accepted Answer

The $K_m$ is close to the substrate concentration.

Question 14

Which of the following is a consequence of having a low $K_m$ enzyme in a metabolic pathway?

Accepted Answer

The enzyme is nearly saturated and operates at close to $V_{max}$ even at low substrate concentrations.

Question 15

Which of the following best explains why glycolysis and gluconeogenesis must be tightly controlled and regulated in conjunction?

Accepted Answer

To prevent futile cycling and waste of cellular resources.

Metabolic Regulation: Enzyme Kinetics and Control in Glycolysis

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