Updated: 3/27/2017

Citric Acid Cycle

0%
Topic
Review Topic
0
0
N/A
N/A
Questions
3 3
0
0
0%
0%
Evidence
1 1
0
0
0%
0%
Videos
3 3
 

 
Overview 
  • Other names 
    • Krebs cycle, tricarboxylic acid (TCA) cycle
  • Function
    • generate high amounts of NADH/FADH2 that act as fuel for ATP synthesis in the electron transport chain
  • Pathway
    • occurs in the mitochondria
    • requires O2 to function
    • net equation
      • acetyl-CoA + 3 NAD+ + FAD + GDP + Pi → 2CO2 + 3 NADH + FADH2 + GTP + CoA
        • will theoretically yield 12 ATP (if ETC were 100% efficient)
        • both carbons of acetyl-CoA leave as CO2 in two of the reactions
          • conversion of isocitrate to alpha ketoglutarate
          • conversion of alpha ketoglutarate to succinyl-CoA
    • Important enzymes
      • isocitrate dehydrogenase
        • stimulated by ↓ energy
          • ↑ ADP
        • inhibited by ↑ energy
          • ↑ ATP, NADH
      • α-ketoglutarate dehydrogenase complex 
        • requires the same cofactors as the pyruvate dehydrogenase complex
          • B1, B2, B3, B5, lipoic acid
          • in alcoholics, Bdeficiency leads to Wernicke's encephalopathy
            • triad of ataxia, confusion, ophthalmoplegia  
          • inhibited by ↑ energy
            • ↑ ATP, NADH
          • inhibited by ↑ intermediates in the cycle
            • ↑ succinyl-CoA
      • succinyl-CoA synthetase
        • generates GTP
      • succinate dehydrogenase
        • a member of both the citric acid cycle and the electron transport chain
    • important intermediates
      • citrate
        • functions to shuttle acetyl-CoA out of mitochondria for fatty acid synthesis
          • citrate shuttle
      • succinyl-CoA
        • building block for heme synthesis
      • fumarate
        • enters from the urea cycle
      • malate
        • functions as a gluconeogenic substrate
  • Regulation
    • energy status control
      • NO hormonal control
 
 

Please rate topic.

Average 5.0 of 10 Ratings

Questions (3)
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK

(M1.BC.12.1) A 54-year-old male with a history of alcoholism is admitted to your service with ataxia, ophthalmoplegia and altered mental status. Which reaction below is likely impaired in this man? Tested Concept

QID: 100066
FIGURES:
1

Conversion of a-ketoglutarate to succinyl-CoA

68%

(202/296)

2

Conversion of succinate to fumarate

3%

(10/296)

3

Condensation of acetyl-CoA with oxaloacetate to form citrate

12%

(36/296)

4

Conversion of fumarate to malate

4%

(13/296)

5

Formation of oxaloacetate from malate

10%

(31/296)

M 1 E

Select Answer to see Preferred Response

Evidence (1)
VIDEOS (3)
Topic COMMENTS (10)
Private Note