Q: An enzyme has $$k_{cat} = 100~s$$^{-1}$$, K_m = 50$$~\mu M$$, and $$[E] = 10~nM$$. What is the initial rate v_0$ when $$[S] \gg K_m$$?

$$v_0 = k$$_{cat} [E] = 1 \times $$10^{-6}$$~M~$$s^{-1}$$

Question 1

Which of the following best describes the rate law for a simple first-order reaction where $$A \rightarrow$$ Products?

Accepted Answer

Rate $$= k[A]$$

Question 2

In Michaelis-Menten kinetics, which assumption allows the simplification of the rate equation by ignoring the reverse reaction from product to substrate?

Accepted Answer

The product concentration is negligible during initial velocity measurements.

Question 3

A double reciprocal (Lineweaver-Burk) plot of enzyme kinetics has $$1/v on $$the y-axis and $$1/[S] on $$the x-axis. What does the y-intercept represent?

Accepted Answer

$$1/V_{max}$$

Question 4

If the total enzyme concentration is increased, what effect does this have on the intercept of a double reciprocal plot?

Accepted Answer

The y-intercept remains unchanged.

Question 5

Given the rate of formation of the enzyme-substrate complex $$ES is$$ $$d[ES]/dt = k_1$[E][S]$$, what is the unit of $$k_1$$?

Accepted Answer

$$M^{-1}$$ $$s^{-1}$$

Question 6

If $$k_2 is $$very small compared to $$k_{-1}$$, what is the unit for $$k_2 in $$the Michaelis-Menten mechanism?

Accepted Answer

$$s^{-1}$$

Question 7

An enzyme has $$k_{cat} = 100~s$$^{-1}$$, K_m = 50$$~\mu M$$, and $$[E] = 10~nM$$. What is the initial rate v_0$ when $$[S] \gg K_m$$?

Accepted Answer

$$v_0 = k$$_{cat} [E] = 1 	imes $$10^{-6}$$~M~$$s^{-1}$$

Question 8

What is the efficiency of an enzyme, as defined by $$k_{cat}/K_m$$?

Accepted Answer

It measures how efficiently an enzyme converts substrate to product at low substrate concentration.

Question 9

Which step is rate-limiting in a two-step enzymatic reaction where $$k_2$$ \gg $$k_1$$ and $$k_3 is $$negligible?

Accepted Answer

The first step ($$k_1)$$

Question 10

Which of the following is true about competitive inhibition?

Accepted Answer

It increases $$K_m$$ but does not affect $$V_{max}.$$

Question 11

Which of the following statements about irreversible inhibitors is correct?

Accepted Answer

They form covalent bonds with the enzyme, permanently inactivating it.

Question 12

What is the effect of a non-competitive inhibitor on $$V_{max}$$ and $$K_m$$?

Accepted Answer

$$V_{max}$$ decreases, $$K_m$$ unchanged

Question 13

Which of the following is a correct unit for $$K_m in $$Michaelis-Menten kinetics?

Accepted Answer

$$M$$

Question 14

How does increasing substrate concentration $$[S]$$ affect $$V_{max} in $$Michaelis-Menten kinetics?

Accepted Answer

$$V_{max}$$ remains unchanged as $$[S]$$ increases

Question 15

Which of the following best describes the graphical difference between enzymatic and non-enzymatic conversion of substrate to product?

Accepted Answer

Enzymatic conversion shows a hyperbolic curve of velocity vs. substrate concentration.

Question 16

Which of the following is a key assumption of Michaelis-Menten kinetics?

Accepted Answer

The formation and breakdown of the enzyme-substrate complex are at steady state.

Question 17

What is the effect of a competitive inhibitor on a Lineweaver-Burk plot?

Accepted Answer

The x-intercept moves closer to zero.

Question 18

Which of the following best explains why hemoglobin (Hb) displays a sigmoidal oxygen saturation curve while myoglobin (Mb) displays a hyperbolic curve?

Accepted Answer

Hb exhibits cooperative binding of oxygen, while Mb does not.

Question 19

Which of the following changes occurs at the allosteric site of hemoglobin when it transitions from the deoxy (T) to the oxy (R) form?

Accepted Answer

The allosteric site becomes less accessible to 2,3-BPG.

Enzyme Kinetics, Inhibition, and Hemoglobin Function: Study Notes for Biochemistry

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