Metabolism and its Control 2

Question 1

Conversions of one TCA cycle

Answer 1

• Acetyl-CoA –> CoA + 2 CO2
• 3 NAD+ –> 3 NADH
• FAD –> FADH2
• GDP + Pi –> GTP

Question 2

How many NADH/FADH2 molecules are there after glycolysis and TCA cycle?

Answer 2

• 10 NADH
• 2 FADH2

Question 3

Where are all enzymes for the ETC found?

Answer 3

In inner mitochondrial membrane

Question 4

Equation for oxidation of NADH

Answer 4

NADH + H+ –> NAD+ + 2H+ + 2e-

Question 5

Which complexes do the 2e- from NADH pass through?

Answer 5

I and III

Question 6

How many H+ are moved into the intermembrane space by complexes I and III with NADH’s 2e-?

Answer 6

4H+ each

Question 7

How much ATP is made from each NADH/FADH2?

Answer 7

• NADH = 2.5
• FADH2 = 1.5

Question 8

How many H+ make 1 ATP?

Answer 8

3

Question 9

Equation removing e- from ETC

Answer 9

2e- + 2H+ + 1/2O2 –> H2O

Question 10

What complex catalyses the transfer of e- to molecular oxygen to remove them from ETC?

Answer 10

Complex IV (cytochrome c oxidase)

Question 11

What can inhibit complex IV?

Answer 11

• Cyanide
• Carbon monoxide
• Azide

Question 12

Mechanisms to enable reducing equivalents to be transferred from cytosol into mitochondria for the ETC

Answer 12

• Glycerol phosphate shuttle
• Malate/aspartate shuttle

Question 13

How does the glycerol phosphate shuttle work?

Answer 13

• Cytosolic NADH used to reduce DHAP into glycerol-3-phosphate through cytosolic glycerol-3-phosphate dehydrogenase
• Glycerol-3-phosphate diffuses into mitochondria
• Glycerol-3-phosphate oxidised by mitochondrial glycerol-3-phosphate dehydrogenase into DHAP and FADH2

Question 14

How does the malate aspartate shuttle work?

Answer 14

• Oxaloacetate reduced into malate by malate dehydrogenase (used NADH)
• Malate diffuses into mitochondria
• Original reaction reversed inside mitochondria by mitochondrial malate dehydrogenase (releases NADH)
• OAA transaminated to aspartate which is transported into the cytosol
• Aspartate converted back to OAA by cytosolic aspartate aminotransferase

Question 15

How does brown adipose tissue maintain body temperature?

Answer 15

Mitochondria are largely uncoupled, so energy is released as heat instead of ATP

Question 16

Where are the different glucose transporters found?

Answer 16

• GLUT1 = all mammalian tissues
• GLUT2 = liver cells, pancreatic beta cells
• GLUT3 = all mammalian tissues
• GLUT4 = muscle cells, fat cells

Question 17

What are the roles of the different glucose transporters?

Answer 17

• 1 = basal glucose uptake
• 2 = remove excess glucose from blood in liver, role in regulation of insulin in beta cells
• 3 = basal glucose uptake
• 4 = basal glucose uptake