Chapter 23, Problem 23.51UTC

Interpretation Introduction

Interpretation:

Each of the given chemical compounds should be identified as a part of the citric acid cycle, electron transport chain or both.

Concept introduction:

► Citric acid cycle includes various reactions which occur in living cells during aerobic respiration. In this cycle, acetyl-CoA is oxidized for releasing carbon dioxide and energy in the form of ATP.

► Electron transport chain is the last step of aerobic respiration and includes a sequence of redox reactions which occur by transporting electrons along with hydrogen ions across the mitochondrial membrane.

To identify: Each of the given compounds as a part of citric acid cycle, electron transport chain or both.

Answer to Problem 23.51UTC

Solution:

(a) Citric acid cycle.

(b) Electron transport chain.

(c) Both citric acid cycle and electron transport chain.

(d) Electron transport chain.

(e) Citric acid cycle.

Explanation of Solution

(a) Succinate is a chemical species formed from Succinyl CoA during citric acid cycle. It produces fumarate after its reaction with succinic dehydrogenase.

For this reason, succinate is a part of citric acid cycle.

(b) $CoQ{H}_2$ is a chemical species that produces complex III along with cytochrome c reductase ($CoQ{H}_2$-cytochrome creductase complex) and helps in transfer of electrons.

For this reason, $CoQ{H}_2$ is a part of electron transport chain.

(c) FAD (Flavin adenine dinucleotide) is a cofactor of redox reactions. It helps in controlled redox reactions in both citric acid cycle and electron transport chain and releases energy as ATP.

For this reason, FADis a part of both citric acid cycle and electron transport chain.

(d) Cyt c (Fe²⁺) is a type of hemeprotein found in mitochondrial membrane. It participates in electron transport chain and helps in transfer of electrons.

For this reason, cyt c (Fe²⁺) is a part of electron transport chain.

(e) Citrate is a chemical species formed from acetyl-CoA during citric acid cycle. It produces cis-aconitate after its reaction with aconitase.

For this reason, α-ketoglutarate is a part of citric acid cycle.

Conclusion

Each of the given chemical compounds is identified as a part of citric acid cycle, electron transport chain or both.