Question

(L)

If electron transfer in tightly coupled mitochondria is completely inhibited with antimycin A, then:

Group of answer choices

all ATP synthesis will stop.

ATP synthesis will continue, but the P/O ratio will drop to one.

electron transfer from NADH will cease, but O₂ uptake will continue.

electron transfer from succinate to O₂ will continue unabated.

energy diverted from the cytochromes will be used to make ATP, and the P/O ratio will rise.

(M)

You discover an enzyme that catalyzes the following reaction, S ⇌ P.

Given the following table of data, what is the rate constants for conversion of P to S, in the presence and absence of the enzyme. What is the rate constant for enzyme-catalyzed conversion of P to S, called the (k_reverse)_enzyme?

Uncatalyzed (no enzyme)	kforward = 1.8 sec-1	kreverse = 2 × 10-3 sec-1
Catalyzed (enzyme present)	kforward = 2.5 × 103 sec-1	kreverse =  ?

Group of answer choices

(k_reverse)_enzyme = 4.0 × 10^-4 sec^-1

(k_reverse)_enzyme = 1.1 × 10^-2 sec^-1

(k_reverse)_enzyme = 0.18 sec^-1

(k_reverse)_enzyme = 2.8 sec^-1

(k_reverse)_enzyme = 2.5 × 10³ sec^-1

⁽ⁿ⁾

When acetyl-CoA reacts with oxaloacetate to form citrate,

Group of answer choices

a new carbon-carbon bond is formed.

an oxidative decarboxylation reaction takes place.

a dehydration reaction takes place.

a rearrangement takes place.

None of these

Answer 1

L). If electron transfer in tightly coupled mitochondria is completely inhibited with antimycin A, then all ATP synthesis will stop. Antimiycin a blocks electron transport and proton pumping at Complex II. Hence, no electron transport can further occur which cease ATP synthesis. Thus, correct answer is 1st option.

N). When acetyl Co-A reacts with oxaloacetate to form citrate, condensation occurs. The first reaction of the TCA cycle is the condensation of acetyl-CoA with oxaloacetate to form citrate catalyzed by citrate synthase: In this reaction the methyl carbon of the acetyl group is joined to the carbonyl group (C-2) of oxaloacetate. Thus, the correct answer is none of these.