Question 1

Which enzyme catalyzes the first step of the TCA cycle, and what is the effect of NADH on this enzyme?

Accepted Answer

Citrate synthase; NADH inhibits the enzyme

Question 2

Given the reaction: $$	ext{Fumarate} + 	ext{H}_2	ext{O} ightarrow 	ext{L-Malate}$$, which enzyme catalyzes this step in the TCA cycle and what is the standard free energy change ($$\Delta G^\circ'$$)?

Accepted Answer

Fumarase; $$\Delta G^\circ' = -3.8 kJ/$$mol

Question 3

Which of the following statements best describes the relationship between $$K$$ and $$Q in a $$biochemical reaction?

Accepted Answer

$$Q \u003c K$$ means the reaction proceeds forward, $$\Delta G \u003c 0$$

Question 4

Which cofactor is essential for the decarboxylation of pyruvate in the pyruvate dehydrogenase complex?

Accepted Answer

TPP (thiamine pyrophosphate)

Question 5

In the regulation of the TCA cycle, which molecule activates isocitrate dehydrogenase and what is the physiological significance?

Accepted Answer

Ca$$^{2+}$$; increases TCA cycle flux

Question 6

Which step in the TCA cycle is classified as an oxidoreductase reaction and produces NADH?

Accepted Answer

Step 3: Isocitrate dehydrogenase

Question 7

Where does β-oxidation of fatty acids occur in eukaryotic cells, and what is the main product used for energy?

Accepted Answer

Mitochondrial matrix; Acetyl-CoA

Question 8

Which of the following correctly lists the four ordered steps of fatty acid synthesis?

Accepted Answer

Reduction, Dehydration, Reduction, Transfer to another

Question 9

During the electron transport chain (ETC), what is the correct order of electron flow starting from NADH?

Accepted Answer

NADH → Complex I → Ubiquinone (Q) → Complex III → Cytochrome b → Complex IV → Ubiquinone (Q$$_2)$$

Question 10

What is the primary function of the Q cycle in the electron transport chain?

Accepted Answer

Transfers electrons from QH$$_2 to $$cytochrome c and pumps H$$^+$$

Question 11

In the light reaction of photosynthesis, which molecule is oxidized first and what is the final product of the reduction pathway?

Accepted Answer

H$$_2O is $$oxidized first; NADPH is the final product

Question 12

Which stage of CO$$_2$$ assimilation involves the regeneration of ribulose 1,5-bisphosphate?

Accepted Answer

Stage 3: Regeneration of acceptor

Question 13

How many essential amino acids are there, and which of the following is NOT considered essential?

Accepted Answer

10; Tyrosine

Question 14

Which amino acid biosynthetic family is derived from phosphoenolpyruvate and erythrose-4-phosphate?

Accepted Answer

Phenylalanine, Tyrosine, Tryptophan

Question 15

Which amino acids are both glucogenic and ketogenic?

Accepted Answer

Phenylalanine, Isoleucine, Tyrosine, Tryptophan, Threonine

Question 16

A patient has a deficiency in pyruvate dehydrogenase. Which metabolic pathway would be most directly affected?

Accepted Answer

TCA cycle

Question 17

Which of the following is a multienzyme complex, and what is its primary function?

Accepted Answer

Pyruvate dehydrogenase complex; catalyzes conversion of pyruvate to acetyl-CoA

Question 18

Which process is anabolic and occurs in the cytosol?

Accepted Answer

Fatty acid synthesis

Question 19

Which molecule is the final electron acceptor in the mitochondrial electron transport chain?

Accepted Answer

O$$_2$$

Comprehensive Study Notes: Central Metabolic Pathways and Regulation in Biochemistry

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