Prep and Harvest TCA CYCLE Flashcards
- Where does the citric acid cycle take place? What are the steps converting pyruvate to
acetyl CoA? 9
Citric acid cycle takes place in mitochondrial matrix. CAC is aerobic always
Steps converting pyruvate to acetyl CoA (irreversible):
Pyruvate react with CoA and NAD+ to form Acetyl coA and NADH and Co2 + H+ using Pyruvate DH enzyme.
pyruvate is oxidatively decarboxylated.
end product ( CO2, 2 electrons, acetyl coa)
Steps:
1. decarboxylation of pyruvate, 2. oxidation of TPP, formation of acetyl coa
*Understand how the pyruvate dehydrogenase complex is regulated (Figure 18.10).
pyruvate dh- TPP- E1
dihydrolipoyl tran- Lipoamide- E2
dihydrolipyl dH- FAD- E3
MIGHT NOT NEED TO KNOW ON EXAM.
*What is lactic acidosis?
Lactic acidosis- high blood concentration of lactic acid.
caused due to people being deficient in phosphatase, which caused pyruvate DH to always be phosphorylated and inactive.
once pyruvate DH is inactive, glucose has to take anaerobic path to make acetyl coa through lactic acid formation (resulting in a lot of lactate buildup).
*What are the clinical symptoms of Beriberi? What causes Beriberi?
symptoms: muscle weakness, pain in limbs, skin distorted sensation, enlarged heart.
Beriberi is deficicency in Thiamin Vitamin B1 (TPP cannot be formed)DO not need to know.
*Understand the overall function of the citric acid cycle (CAC) in terms of the reactions and
what byproducts it produces.
key function of citric acid cycle: harvest high-energy electrons from carbon fuels.
CAC oxidizes acetly fragment of Acetyl CoA to Co2
Get a total of 2 Co2, and 8 electrons (6 e- from NADH, and 2 e- from FADH2).
in oxidation, high energy e- captured in form of NADH and FADH2.
*Be able to identify the steps in the CAC that produce NADH, FADH2 and ATP.
2c acetyl group combines with 4c oxaloacetate to form 6c Citrate.
Citrate will then undergo decarboxylation and generate 2 molecules of CO2, which also releases electrons in form of NADH and FADH2.
Then oxaloacetate (4c) is regenerated and e- in NADH and FADH2 eventually used to power synthesis of ATP in oxidative phosphorylation.
*Understand where succinate dehydrogenase is located in the mitochondria and why it
utilizes FAD instead of NAD.
Succinate DH embedded in the inner mitochondrial membrane along with ETC
FAD used because the free energy change not sufficient to reduce NAD
Succinate transfers 2 electrons from FADH2 to Coenzyme.
(DO WE REALLY NEED TO KNOW THIs!!!!)
- Have an appreciation for the free-energy changes that occur throughout the cycle (i.e. Table
19. 1).
dont need to know. starts from negative delta g to positive delta g
*Understand why and how concentrations of citric acid cycle intermediates change
immediately after the addition of malonate.
malonate-inhibitor of succinate DH, which will increase build up of succinate, decrease rate of CAC (going backwards)
*Understand the control points of the citric acid cycle (figure 19.7
key control points of CAC are reactions catalyzed by isocitrate DH and alpha-ketoglutarate DH.
ATP and NADH will inhibit isocitrate DH; ADP will activate it.
ATP, succinyl coa, NADH will inhibit alpha ketoglutarate.
alpha ketogluatarate catalyzes rate limiting step in CAC. (enzyme functions similar to Pyruvate DH)
recall pyruvate DH controls entry of glucose derived acetyl coa into cycle.
*Why is isocitrate dehydrogenase considered the rate-limiting step in the CAC?
it controls the rate of CAC, as it catalyzes the oxidation that generates first high transfer potential electron in NADH.
Understand what an anaplerotic reaction is. Can you explain it in terms of oxaloacetate and
pyruvate carboxylase?
Anaplerotic reactions- reactions that replenish the citric acid cycle components, if energy status of cells change.
since CAC provides precursors for biosynthesis, you need replenishing rxns.
ex: Pyruvate carboxylase catalyzes a replenishing reaction of generating oxaloacetate directly in mitochondria from pyruvate (pyruvate and ATP form oxalacetate and ADP and pi)
pyruvate to acetyl coa and fatty acid to acetyl coa also replenishing reactions.
What are the two main parts in CAC?
What are the total number products of ATP, electron carriers generated for 1 CAC Cycle?
first part- 2c couple with 4c oxaloacetate to form citrate (also generate 2 Co2 after 2 oxidative decarboxylations)
second part- regenerate oxaloacetate
What are the total number products of ATP, electron carriers generated for 1 CAC Cycle?
1 CAC cycle generates:
1 ATP, 2 CO2, 3 NADH, 1 FADH2 (total of 8e-), 1 CoA
How many ATP will e- from NADH and FADH2 generate?
NADH- electrons generate 2.5 ATP.
FADH2- electrons generate 1.5 ATP.
1 CAC total of 10 ATP
