UW-Madison Biochem 501 Exam 3

Glycolysis location

Cytosol of cell (not mitochondria)

Glycolysis of 1 glucose molecule yields

2 molecules pyruvate, net gain of 2 ATP, 2 NADH

Phosphofructokinase (PFK)

Catalyzes phosphorylation reaction (converts fructose 6-phosphate to fructose 1,6-bisphosphate). It uses ATP as a substrate.

Triose Phosphate Isomerase (TPI)

Catalyzes conversion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate (G3P). Has unfavorable, large, positive ΔG∘, but still procededs forward as glucoses steps consume G3P, keeping its concentration very low

Fermentation purpose

Convert pyruvate to lactate or ethanol, under anaerobic conditions to keep supply of NAD+, so glycolysis can continue running

Citric Acid Cycle Purpose & Location

Purpose: oxidize acetyl-CoA from glycolysis into CO2 to generate NADH and FADH2 to power ATP production in the electron transport chain
Location: mitochondrial matrix

Pyruvate Dehydrogenase (PDH) Complex (3 subunits)

Bridges glycolysis to citric acid cycle.
Consists of 3 subunits:
E1 - catalyzes decarboxylation, required thiamine (as TPP)

E2 - catalyzes oxidation, requires lipoid acid
E3 - Catalyzes electron transfer and requires FAD

Urea Cycle Purpose

Turn toxic ammonium into non-toxic NCH derivative

Urea Cycle General Steps

• Inside mitochondrial matrix, carbamoyl phosphate + ornithine → citrulline

• Citrulline transported out of mitochondria into cytosol.

• Citrulline activated , which requires energy in form of ATP. Activated citrulline hydrolyzed to give pyrophosphate (PPi) and forms citrullyl-AMP intermediate

• Citrullyl-AMP intermediate converted to argininosuccinate, which is then processed into arginine.

• Arginine broken down to release urea and regenerate ornithine (ornithine goes back to mitrochondrial matrix so cycle can continue over again)

Calvin Cycle

CO2 converted to sugar (photosynthesis)