MC Questions BioChem

Question

Hello, any help is appreciated,

A botanist has discovered that the buds of a species of flower have an intense

citrus flavor, but act as a deadly poison when consumed by humans. Which

biochemical mechanism explains both the accumulation of citrate and the

poisonous effects?

a. Cyanide is concentrated in the plant leading to the shut down of the

electron transport chain when it is consumed.

b. The plant produces a high concentration of tryptophan which causes a

negative feedback inhibition of the citric acid cycle when consumed.

c. Arsenite is concentrated in the plant leading to the inactivation of PDH

and thus the citric acid cycle when it is consumed.

d. Fluoroacetate is produced by the plant causing the inhibition of aconitase,

leading to the shut down of the citric acid cycle when consumed.

e. Malonate is concentrated in the plant leading to the inhibition of succinate

dehydrogenase, causing the shut down of the citric acid cycle.

Which steps (enzymes) in the citric acid cycle are

regulated allosterically by high ADP?

a. 1 and 3

b. 2 and 5

c. 1 and 4

d. 1, 4, 5, 7, and 9

e. 1, 4, and 5

Choose the correct path taken by a pair of electrons as it travels down the

electron-transport chain:

a. NADH → complex I → CoQ →Complex II →CoQ → complex III →

complex IV→Cyt c→ O 2 .

b. FADH2 →complex II → CoQ → Complex III →Cyt c →complex IV →

O 2 .

c. NADH → complex II→ CoQ → Complex III → Cyt c → complex IV →

O 2 .

d. FADH2 →complex II→ Cyt c → Complex III →CoQ → complex IV →

O 2 .

e. NADH → complex I → CoQ → Complex II → Cyt c→ Complex III →

Cyt c  complex IV → O 2 .

Answer 1

Hi Rahman W.,

I won't help you with the latter 2 parts -- you have to read up on your citric acid cycle!

With the first part -- fluoroacetate is my choice of poison, see

https://naturespoisons.com/2017/10/05/gifblaar-fluoroacetate-poison/ .

That bit about intense citrus flavor is just to confuse you; if you're perceiving lemonyness that's odorants from terpenic oils, which usually aren't extremely toxic.

Malonate blocks the succinate->fumarate step, which is different; it's widely distributed in plants but especially rich in certain legumes. Arsenite affects oodles of enzymes, so it wouldn't be specific.

-- Cheers, -- Mr. d.