Thompson 3

Question 0

What enzymes are used to defend against ROS?

Answer 0

Superoxide dismutase, glutathione peroxidase, glutathione reductase, catalase

Question 1

In general terms, how does oxidative phosphorylation create energy?

Answer 1

The energy released by the reactions of the TCA cycle and other oxidative pathways is almost entirely conserved in reducing agents (NADH, FADH2). When oxidized by the enzymes of the ETC, their electrons are transferred to oxygen, reducing it to water and creating an electrochemical (proton) gradient in the process. This electrochemical potential is used by ATP synthase to generate ATP.

Question 2

The antioxidant enzymes are most abundant in what tissues?

Answer 2

Liver, adrenal gland, kidney

High mitochondria and peroxisome content

Question 3

Glutathione __________ reduces _____ to water, using glutathione as a cofactor, which is recycled by glutathione _______ and ______ for reducing equivalents (GSSG -> 2 GSH).

Answer 3

peroxidase, hydrogen peroxide, reductase, NADPH + H+

Question 4

What is the purpose of the pentose phosphate pathway?

Answer 4

• To generate reducing equivalents (NADPH) for other pathways (fatty acid/cholesterol/steroid synth, detox, ROS reduction, nitric oxide synth, others)
• To produce ribose 5-phosphate for nucleotide synthesis.

Question 5

What is the committed step of the PPP?

Answer 5

G6P dehydrogenase (first step)

Question 6

Which enzyme of the PPP transfers 2 carbons? What cofactor does it use?

Answer 6

Transketolase, TPP

Question 7

Which enzyme of the PPP transfers 3 carbons?

Answer 7

Transaldolase

Question 8

The ____ phase of the PPP produces reducing agents for other pathways and the _____ phase produces glycolytic intermediates.

Answer 8

Oxidative (irreversible), nonoxidative (reversible)

Question 9

G6P dehydrogenase deficiency results in hemolysis of RBCs due to an inability to form _____, which is required for ROS reduction.

Answer 9

NADPH

Question 10

_____ is the most common human enzyme defect.

Answer 10

G6PD deficiency

Question 11

Why is the PPP important in RBCs? What is observed in the Mediterranean population? What do fava beans have to do with it?

Answer 11

• The G6PD / NADPH pathway is the only source of reduced glutathione in RBCs. The role of RBCs as oxygen carriers puts them at substantial risk of damage from ROS.
• Highest prevalence of G6PD deficiency, susceptible to hemolytic crises (thought to be the result of an evolutionary resistance to plasmodium vivax/p. falciparum, which is why oxidative anti-malarials are contraindicated)
• Fava beans contain many oxidative compounds, puts too much oxidative stress on individuals with G6PD deficiency

Question 12

Heinz bodies are clumps of what?

Answer 12

Denatured Hb in RBCs (a sign of hemolytic anemia, caused by oxidative damage secondary to G6PD deficiency, other disorders)