TCA cycle Flashcards
(20 cards)
Where does the TCA cycle occur? Is this process aerobic or anaerobic. What is the end goal?
Occurs in the matrix. This is a part of aerobic respiration.
It is a series of redox reactions that generate 2 CO2, 3 NADH, 1 FADH2, per molecule of acetyl CoA
Where is the TCA cycle most active
Most active in brain, heart, kidney cortex, and liver
step 1 of the TCA cycle
Aldol condensation:
catalyzed by enzyme CITRATE SYNTHASE (irreversible)
Acetyl CoA (from PDH) and Oxaloacetate (prod of cycle) are with water to form water and CITRATE
step 2 of the TCA cycle
Dehydration reaction:
catalyzed by enzyme ACONITASE (reversible)
Citrate is dehydrated into ISOCITRATE
It’s intermediate form “CIS-ACONITATE” forms first then gets hydrated to isocitrate.
step 3 of the TCA cycle
Oxidation-Carboxylation reaction: rate limiting step
catalyzed by ISOCITRATE DEHYDROGENASE (irreversible)
reduces 6-carbon isocitrate to 5-carbon a-ketoglutarate
generates 1 NADH, releases 1 CO2 as waste
INHIBITED: ATP , ACTIVATORS: ADP, and Calcium
What inhibits/activates the enzyme that catalyzes the 3rd step of the TCA cycle?
Inhibited by: ATP
Activated by: ADP and Calcium
step 4 of the TCA cycle
Oxidative Carboxylation reaction:
catalyzed by a-ketoglutarate dehydrogenase
a-ketoglutarate + NAD+ and acetyl CoA are made into Succinyl CoA
(CO2, and NADH are by products)
step 5 of the TCA cycle
Substrate level phosphorylation: (reversible)
Catalyzed by Succinyl-CoA synthetase
Converts Succinyl-CoA into Succinate
Converts 1 GDP into a GTP as a by product
Step 6 of the TCA cycle
Oxidation reaction:
Catalyzed by Succinate Dehydrogenase
Converts Succinate into a Fumerate
FAD+ is converted into 1 FADH2
Step 7 of the TCA cycle
Hydration reaction:
catalyzed by Fumerase
catalyzes Fumerate into L-Malate
Step 8 of the TCA cycle
Oxidation reaction:
Catalyzed by Malate dehydrogenase (reversible)
Generate 1 NADH
Results in Malate become Oxaloacetate
Generates 1 NADH from NAD+
What is important about the final product Oxaloacetate?
It is the final product of TCA, but it is sent back into the first step to react with Acetyl CoA to begin the cycle again.
What are the irreversible steps of TCA?
Citrate synthetase, isocitrate dehydrogenase (major), a-ketoglutarate dehydrogenase.
How is citrate synthase regulated?
NADH, succinyl-CoA, citrate, and ATP (inhibitors)
ADP (activator)
How is isocitrate dehydrogenase regulated?
Succinyl-CoA and NADH (inhibitors)
calcium and ADP (activator)
How does mutant Isocitrate dehydrogenase present in some cancers?
Some use NADP+ instead of NAD+
2-hydroxyglutarate accumulates to very high concentrations which inhibits the function of enzymes that are dependent on alpha-ketoglutarate. This leads to a hypermethylated state of DNA and histones, which results in different gene expression that can activate oncogenes and inactivate tumor-suppressor genes. Ultimately, this may lead to different types of cancer.
How are mitchondria moving around the cell?
They are moved around on microtubles
Why would ion transporting cells have mitochondria near them?
many mitochondria are located near basolateral cell membrane infoldings and provide locally needed ATP
What creates the gradient that powers the electron transport chain?
The metabolism of nutrients creates a proton gradient that is used to make ATP
What 3 substrates can become acetyl CoA destined for the TCA cycle?
Fatty Acids
Glucose
Amino Acids
