Lecture 16: Acetyl CoA CAC

Question 1

Know the basic structure of a mitochondria

Answer 1

• Composed of an inner and an outer membrane that define two spaces
• Intermembrane space:
between the two membranes
• Mitochondrial matrix:
the space inside the inner
membrane 
• Stages 2 through 4 of cellular
respiration take place in the
mitochondria

Question 2

Know the Acetyl CoA Synthesis reaction

Answer 2

• In the presence of oxygen: pyruvate is
transported into the mitochondrial matrix and is
converted to Acetyl CoA
• Catalyzed by a group of enzymes called the
Pyruvate Dehydrogenase Complex
• Produces:
2 molecules of CO2
2 molecules of NADH
2 molecules of acetyl CoA

Question 3

Citric Acid Cycle (CAC)

Answer 3

Step 3:
- Isocitrate is oxidized, reducing NAD+ to NADH. Loss of a molecule of
CO2 to form α-Ketoglutarate

Step 4:
- α-Ketoglutarate loses
a molecule of CO2 and
is oxidized, reducing
NAD+ to NADH.
The remaining
molecule is attached to
coenzyme A by an
unstable bond to form
Succinyl CoA

Step 5:
CoA is displaced by a
phosphate group,
which is transferred to
GDP, forming GTP: a
molecule with functions
similar to ATP
GTP can be used to
generate ATP
The molecule
Succinate is formed

Step 6:
Two hydrogens are
transferred from
Succinate to FAD,
forming FADH2 and
oxidizing Succinate to
form Fumarate.

Step 8:
Malate is oxidized,
reducing NAD+ to
NADH and
regenerating
Oxaloacetate

• Products:
  2 ATP
  6 NADH
  2 FADH2
• Oxaloacetate is regenerated