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SW on KREB CYCLE:

Refer to your Kreb Cycle pathway.

The 2 moles of pyruvic acids produced per molecule of glucose from glycolysis in the cytoplasm, now

enters the mitochondria, successively.

Initial Reaction:

pyruvic acid + Co-ASH (co-enzyme A) + NAD+ to produce acetyl CoA + CO2 + NADH + H+ ion as products.

1) What is the role of NAD+?

A) oxidizing

B) reducing agent

2) Considering the products in the conversion of pyruvic acid to acetyl-CoA, what is the reaction

involved?

A) oxidation

B) reduction C) oxidative decarboxylation

* One of the products in the 'initial reaction' is NADH.

Mitochondrial NADH = 3 ATP vs. cytoplasmic NADH produced in glycolysis = 2 ATP.

Refer to Step 1 of Kreb cycle: acetyl-CoA reacts with oxaloacetic acid (an acetly-CoA acceptor) to

produce citric acid.

3) Why is oxaloacetic acid a keto-acid? Encircle in the formula the 2 functional groups present.

4) Count the total no. of C atoms in citric acid that is produced from acetyl-CoA and co-enzyme A (Co-

ASH).

What reaction is involved?

A) redox B) condensation

5) Steps 2 and 3: What are the reactions involved in the formation of isocitric acid?

A) oxidation & reduction B) dehydration & hydration

6) Step 4: The conversion of isocitric to oxalosuccinic acid uses NAD+ to produce NADH.

a) What is the reaction involved?

A) oxidation

B) reduction

b) Encircle in the formulas the changes in the functional groups.

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7) Step 5: The conversion of oxalosuccinic to ketoglutaric removes CO2 as a by-product. The reactions

for steps 4 and 5 can therefore be summarized as:

A) oxidative carboxylation

B) oxidative decarboxylation

8) Step 6: The conversion of ketoglutaric acid to succinyl CoA requires the removal of CO2 and uses

NAD+ and Co-ASH (co-enzyme A) to produce NADH and succinyl-CoA.

What reaction is involved in producing succinyl-CoA?

A) condensation w/ Co-ASH

B) addition rxn to Co-ASH

* In step 7: The conversion of succinyl-CoA to succinic acid produces 1 mole of ATP, as Co-ASH (co-

enzyme A) is removed as by-product.

9) Step 8: The conversion of succinic to fumaric acid uses FAD (role the same as NAD+).

a) What reaction is involved? A) oxidation

B) reduction

b) Encircle in the formulas the changes in the functional groups.

* 1 mole of FADH2 = 2 ATP

10) Step 9: The conversion of fumaric to malic acid, what reaction is involved?

A) hydration

B) dehydration

11) Step 10: The conversion of malic to oxaloacetic acid uses NAD+.

a) What is the reaction involved?

A) oxidative decarboxylation

B) oxidation C) reduction

b) Encircle in the formulas the changes in functional groups.

12) Account for the sum total of ATP produced from glycolysis and Kreb cycle. These should total 36

ATP. (Hint: How many acetyl CoA enters the Kreb cycle per 1 mole of glucose?)