Chapter 10.1

Question 1

Where does the citric acid cycle occur

Answer 1

-it occurs in the mitochondria

Question 2

Where is the PDH complex located

Answer 2

-it is located in the mitochondrial matrix

Question 3

What five enzymes make up PDH complex

Answer 3

1) Pyruvate dehydrogenase
- >pyruvate is oxidized, yielding co2
- >remaining two carbon molecule binds to TPP(coenzyme) by noncovalent interactions

2) dihydrolipoyl transacetylase
- >two carbon molecule bonded to TPP is oxidized and transferred to lipoic acid
- >lipoic acid disulfide group acts as an oxidizing agent and creates the acetyl group
- >after, dihydrolipoyl transacetylase catalyzes the CoA-SH interaction with the newly formed thioester link, forming acetyl coA
- >lipoic acid is left in its recued form

3) dihydrolipoyl dehydrogenase
- >FAD is used as a coenzyme to reoxidize lipoic acid
- >allowing the formation of acetyl coA in future reactrions
- >FAD is reduced to FADH2 to oxidize lipoic acid

4) Pyruvate dehydrogenase kinase
5) Pyruvate dehydrogenase phosphatase
- the last two work in regulating the PDH complex

Question 4

Why is acetyl-coA high energy

Answer 4

-because it has a high energy thioester bond

Question 5

Is coenzyme A a thiol

Answer 5

• yes because it contains a SH group
• when acetyl coA forms, acetyl attaches by covalent attachment to the SH group
• > this results in the formation of a thioester
• > thioester has high energy properties

Question 6

What are other ways(not glycolysis) to form acetyl-coA

Answer 6

1)beta oxidation

2) Amino acid catabolism
- >these amino acids are ketogenic

3)Ketones

4) Alcohol
- >converted by alcohol dehydrogenase and acetaldehyde dehydrogenase