Krebs/Citric Acid Cycle

Question 0

Citric acid cycle

Answer 0

Mitochondria
Major source of oxidative energy production
Pyruvate goes to acetyl-CoA (3C to 2C, remove CO2) by pyruvate dehydrogenase
Enters citric acid cycle
Combines with 4C OAA to make a 6C citrate and the cycle tur s
Both carbons come off as CO2 and off come high energy electrons and GTP
3 carbons in and 3 out as CO2
Products: 3 NADH, 1 FADH2, 1 GTP
2 turns for each glucose

Question 1

Importance of CAC

Answer 1

Hub of metabolism

Catabolism (oxidation) of carbohydrates, proteins, fat as well as biosynthesis of carbohydrates, proteins, and fat

Question 2

FADH2

Answer 2

Energy carrying electrons

Produces 2 ATP

Question 3

NADH

Answer 3

Energy carrying electrons

3 ATP

Question 4

Pyruvate dehydrogenase complex

Answer 4

4 coenzymes, from b-vitamins
Oxidation when we pull of pair of energetic electrons
Decarboxylation
End up with 2C unit acetyl-CoA
Very activated, enters CAC

Question 5

Committed step of the CAC

Answer 5

Citrate

Question 6

Regulation of CAC

Answer 6

Energy rich metabolizes inhibit key enzymes: ATP, NADH, citrate, acetyl-CoA
Citrate synthase is the most important control point
Respiratory control–transfer of electrons and ATP synthesis are linked
ATP production required to convert NADH to NAD
When mito full of ATP, everything slows down
All NADH and FADH2
Maximally stimulated in exercising muscle, increased calcium increases CAC

Question 7

Major site of ATP production

Answer 7

Citric acid cycle
Energy released during CAC is stored as energetic electrons on NADH and FADH2
Converted to ATP in mito

Question 8

Total energy production during glucose

Answer 8

Acetyl-CoA: 9 + 2 + 1 = 12 ATP (3 NADH, 1 FADH2, 1 GTP)
Pyruvate: 12 + 3 = 15 ATP (1 NADH)
Glucose: 30 + 2 + 4 = 36 ATP (2 ATP, 2 NADH)
38 if liver and heart

Question 9

Energy production from anaerobic glycolysis

Answer 9

2 ATP and 2 lactates
Just glycolysis
Pyruvate is converted to lactate to make new glucose

Question 10

CAC and fat metabolism

Answer 10

Fed state: acetyl-CoA—–> fatty acid which is stored as triglyceride

Fasting state: FA released from adipose. Oxidized in tissues to acetyl-CoA then through CAC to produce ATP
acetyl-CoA can form glucose and amino acids

Question 11

CAC and protein metabolism (amino acids)

Answer 11

Carbon skeleton of any amino acids that feed into CAC as NEW intermediate are good for making glucose
Liver can use them to make new glucose during fasting
Good for making ATP and fat as well
Cannot make we Glucsoe!

You can make fats from proteins and carbohydrates
Cannot make new glucose from fats