Question 1

Which of the following best describes the meaning of $$\Delta G in a $$chemical reaction?

Accepted Answer

$$\Delta G$$ represents the change in free energy, indicating whether a reaction is spontaneous.

Question 2

An enzyme catalyzes a reaction by:

Accepted Answer

Decreasing the activation energy required for the reaction to proceed.

Question 3

Which of the following is a key difference between substrate-level phosphorylation and oxidative phosphorylation in cellular respiration?

Accepted Answer

Substrate-level phosphorylation directly transfers a phosphate group to ADP from a substrate, while oxidative phosphorylation uses a proton gradient and ATP synthase.

Question 4

During glycolysis, which enzyme catalyzes the key regulatory step, and what is the significance of this step?

Accepted Answer

Phosphofructokinase; it controls the rate of glycolysis by catalyzing the phosphorylation of fructose-6-phosphate.

Question 5

Which of the following statements about ATP is correct?

Accepted Answer

ATP stores energy in the bonds between its phosphate groups, which can be released during hydrolysis.

Question 6

In the light-dependent reactions of photosynthesis, which two complexes are primarily involved, and what are their main contributions?

Accepted Answer

Photosystem II and Photosystem I; they capture light energy to produce ATP and NADPH.

Question 7

Which pigment is most important for photosynthesis in plants, and what is its primary function?

Accepted Answer

Chlorophyll a; it absorbs light energy, primarily in the blue and red wavelengths, to drive photosynthesis.

Question 8

What is the main purpose of fermentation in cells?

Accepted Answer

To regenerate NAD$$^+ so $$glycolysis can continue in the absence of oxygen.

Question 9

Which of the following best describes the role of Rubisco in the Calvin Cycle?

Accepted Answer

Rubisco catalyzes the fixation of CO$$_2 to $$ribulose-1,5-bisphosphate, forming 3-phosphoglycerate.

Question 10

Which of the following scenarios would most likely increase the rate of an enzyme-catalyzed reaction?

Accepted Answer

Increasing the concentration of substrate up to the point of enzyme saturation.

Question 11

Which equation correctly relates enthalpy ($$H$$), entropy ($$S$$), and free energy ($$G) in $$biological systems?

Accepted Answer

$$\Delta G = \Delta H - T \Delta S$$

Question 12

During cellular respiration, where does the electron transport chain occur, and what is its main product?

Accepted Answer

In the mitochondrial inner membrane; producing ATP via oxidative phosphorylation.

Question 13

Which of the following is true about lactic acid fermentation?

Accepted Answer

It occurs in muscle cells and produces lactate from pyruvate.

Question 14

How are the light-dependent and light-independent reactions of photosynthesis related?

Accepted Answer

The light-dependent reactions generate ATP and NADPH, which are used in the light-independent reactions to fix carbon.

Question 15

Which of the following is a way that enzyme activity can be regulated in a cell?

Accepted Answer

By feedback inhibition, where the end product of a pathway inhibits an earlier step.

Question 16

Which step in cellular respiration produces the most ATP?

Accepted Answer

Oxidative phosphorylation (electron transport chain and chemiosmosis)

Question 17

Which of the following is NOT a product of the citric acid cycle?

Accepted Answer

Glucose

Question 18

A mutation causes Rubisco to lose its ability to bind CO$$_2. $$What would be the most immediate effect on the Calvin Cycle?

Accepted Answer

Carbon fixation would stop, halting the production of 3-phosphoglycerate.

Question 19

Which of the following best explains why ATP is considered the 'energy currency' of the cell?

Accepted Answer

ATP hydrolysis releases energy that can be used to drive endergonic reactions.

Unit 3: Energy, Enzymes, Cellular Respiration, and Photosynthesis

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