Catabolic Metabolism: Krebs Cycle and Oxidative Phosphorylation

Question 1

Relate the enzyme names with the reaction they catalyze in the Kreb’s cycle.

Answer 1

Synthase - forms the compound (citrate synthase catalyzes the formation of citrate)

Synthetase - catelyzes the formation of a compound with the formation of ATP (Succinyl CoA Synthetase catalyzes the formation of Succinate with the formation of ATP

Dehydrogenase - removes hydrogen from compound and forms NADH from NAD+ (Malate Dehydrogenase removes H from Malate and forms NADH)

Question 2

Explain the role of Krebs cycle in metabolism of fatty acid and ketone bodies.

Answer 2

Fatty acids and Ketone bodies are both converted to acetyl CoA and then incorporated into the Kreb cycle

Question 3

Compare the two ways that glycolytic NADH + H+ is shuttled into the mitochondria during oxidative metabolism.

Answer 3

Proton Channel Pumps - Complex I and IV act as channel pumps electrons are moved through them (FMN + FeS in Complex I and CuS + cyto a in Comples IV). 4 H+ are shuttled through Complex I. 2 H+ are shuttled through Complex IV

Internal Rxns - Complex III brings H+ into the intermitochondrial membrane space through internal Rxm

FADH - H+ are brought in through internal Rxns with Complex II

Question 4

Diagram the movement of electrons and hydrogens through electron transport complexes from NADH + H+ and FADH2 to oxygen.

Answer 4

NADH
-H+: NADH-FMNH2-CoQH2-Complex III - intermembrane space

-electrons: NADH-FMNH2-FeS-CoQH2-Complex III-Cyto C - CuS-oxygen

FADH2
-H+: FADH2 - CoQH2 - Complex II - intermembrane space

-electrons: FADH2 -FeS-heme b-CoQH2-Complex III-Cyto C-CuS-oxygen

Question 5

Compare the ATP produced from monosaccharides to that produced from fatty acids

Answer 5

Glucose = 30-32 ATP
Fatty Acid (x carbons) = 7x-6

Question 6

Identify the inhibitors of specific electron-transport complexes

Answer 6

Complex I - Rotenone, Ptericidin, Amytal, Mercurial, Demerol

Complex II - Thenoyiti-Fluoroacetone, Carbonxin

Complex III - Antimycin

Complex IV - Cyanide Azide

ATP Synthase - DCCD Oligomycin

Question 7

Explain the use of proteins to uncouple electron transport from ATP synthesis.

Answer 7

Uncouplers: UCP1 (thermogenin in brown adipose), Dicumerol, FCCP, 2,4-dinitrophenol
thermogenin = protein channel causes proteins to leak through membrane w/o producing ATP. rapidly produces heat instead

Question 8

Emphasize the role of glutathione in relief of cellular oxidative stress

Answer 8

The presence of oxygen and the movement of high energy electrons cause the formation of reactive oxygen species - super oxide dismutase turns ROS into peroxide which is then converted to water by glutathione