Question

RELATED TO CELLULAR RESPIRATION

1. Drug A inhibits citrate synthase, an enzyme that catalyzes the synthesis of citrate in the citrate acid cycle. In cells treated with Drug A, - Indicate whether the statements below are TRUE or FALSE.

Acetyl-CoA levels will increase

CO2 production will increase

The rate of ATP production will decrease

NADH will accumulate in the cell.

2. Drug B prevents NADH from donating electrons to Complex I in the ETC. Indicate whether the statements below are TRUE or FALSE.

The rate of ATP production will increase

Oxygen consumption will increase.

Fes in Complex I will stay in the reduced form.

FADH2 can still donate electrons to Complex II.

3. Drug C acts as a channel in the mitochondrial inner membrane and allows protons to pass freely between the matrix and the intermembrane space. Indicate whether the statements below are TRUE or FALSE.

The ATP level in the cell will increase.

The pH of the mitochondrial intermembrane space will decrease.

The rate of glycolysis will increase.

The rate of CO2 production will decrease.

Oxygen consumption will decrease.

NADH will not be oxidized to NAD+.

The rate of fatty acid catabolism will likely increase

Answer 1

1.

Acetyl-CoA levels will increase TRUE

The acetyl CoA won't be used up to form citrate with oxaloacetate due to drug A. Thus it will accumulate

CO2 production will increase FALSE

CO2 is liberated when TCA cycle takes place. Drug A will block citrate synthase which catalyzes the first step of TCA cycle. Thus TCA will stop and thus CO2 production will decrease

The rate of ATP production will decrease TRUE

Since TCA cycle is blocked, the NADH, FADH2 and GTP won't be formed. Thus ATP production will decrease.

NADH will accumulate in the cell. FALSE

The NADH formed by glycolysis, fatty acid catabolism, and other sources would continue giving electrons for oxydative phosphorylation. Thus they won't accumulate

2.

The rate of ATP production will increase FALSE

The complex I containing NADH dehydrogenase will not be able to oxidize NADH to release its electrons. Thus the contribution in ATP production from NADH will virtually disappear. Hence rate of ATP production will decrease

Oxygen consumption will increase. FALSE

The electrons of the electron transport chain are finally used to reduce oxygen into water. However, since contribution of electrons from NADH is not present in this case, oxygen consumption cannot increase at all

Fes in Complex I will stay in the reduced form FALSE

The iron sulphur clusters (FeS) in complex I get reduced when they get electrons from NADH. However, since the complex is now deactivated, FeS will stay in oxidized form.

FADH2 can still donate electrons to Complex II. TRUE

Although complex I is inactive, complex II will still remain functional and hence FADH2 can donate its electrons to complex II (succinate dehydrogenase)

3.

The ATP level in the cell will increase. FALSE

The drug C acts as an uncoupler by dissipating the proton gradient. Thus, without this gradient, ATP synthesis by oxidative phosphorylation cannot happen

The pH of the mitochondrial intermembrane space will decrease. TRUE

When the proton gradient is dissipated, the protons will enter the intermembrane space and thus the pH there will become acidic (that is pH will decrease)

The rate of glycolysis will increase. TRUE

Since ATP synthesis would not occur by oxidative phosphorylation, the cell will meet its ATP demands by the substrate level phosphorylation of glycolysis. Thus glycolysis will increase

The rate of CO2 production will decrease. FALSE

CO2 is produced in TCA cycle. Since TCA cycle remains undisturbed, CO2 production will not decrease

Oxygen consumption will decrease.   FALSE

The electron transport through the various complexes till finally conerting O2 to H2O will continue. Thus, oxygen consumption will not decrease

NADH will not be oxidized to NAD+.   FALSE

NADH is oxidized to NAD+ at complex I which is a part of electron transport chain and is unaffected here. Thus NADH will continue to get oxidized into NAD+

The rate of fatty acid catabolism will likely increase FALSE

Fatty acid catabolism produces NADH which is then used for ATP synthesis. Since there is no scarcity of NADH but the actual scarcity is of ATP, the cell will not increase fatty acid catabolism rate.

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