TCA/ Krebs Cycke Flashcards
How many reactions make up the TCA cycle
8
Is the TCA cycle aerobic or anaerobic
Aerobic
What is the TCA cycle
Oxidation pathway for CHA, lipids and proteins that generates energy or intermediates (e.g.NADH) to be used in the electron transfer chain for energy and provides several precursors for other metabolic pathways
Where does the TCA cycle occur
In the mitochondria
What does the TCA cycle start with
Acetyl CoA
What occurs in the link reaction
Pyruvate is converted to Acetyl CoA by Pyruvate Dehydrogenase complex (PDH), CO2 and NAD+ are produced
What two forms does PDH exist in
Active and inactive
What is the difference between the active form and inactive form of PDH
Inactive is phosphorylated and active is not
What enzyme inactives PDH
PDH kinase
When is PDH kinase upregulated
When cell energy is plentiful or demand is low
In the presence of what molecules is PDH kinase up regulated (signs of high energy)
High NADH, ATP and acetyl CoA
What enzyme activates PDH
PDH Phosphotase
When is PDH phosphatase upregulated
When energy in the cell is low
In the presence of what molecules is PDH kinase up regulated (signs of low energy status)
High levels of pyruvate, NAD+, ADP, Ca2+ and coASH
Why is PDH activated during exercise
Exercise increases pyruvate and ADP and muscle contraction increases Mg+ and Ca2+ (which are both allosteric regulators of PDH)
When is PDH activated and why
When cell energy is low as PDH activates the TCA cycle so we can start to derive energy from ATP and NADH in this process
What are the main products of the TCA cycle
1 ATP, 3 NADH and 1 FADH2
What reaction does citrate synthase catalyse in the TCA cycle
Oxaloacetate + Acetyl CoA = Citrate
What is the function of the enzyme Isocitrate dehydrogenase in the TCA cycle
Catalyses the reaction of iso citrate to alpha ketogluterate, which simultaneously produces 1 NADH from NAD+
What is the function of the enzyme alpha ketoglutarate dehydrogenase in the TCA cycle
Catalyses the reaction of alpha ketogluterate to succincyl CoA, which simultaneously produces 1 NADH from NAD+
What is the function of the enzyme succincyl CoA synthase in the TCA cycle
Catalyses the reaction of succincyl CoA to succinate, which simultaneously produces one molecule of ATP from Guanine Triphosphate (GTP)
What is the function of the enzyme succinate dehydrogenase in the TCA cycle
Catalyses the reaction of succinate to fumerate, which simultaneously produces 1 FADH2 from FAD
What is the function of the enzyme Malate dehydrogenase in the Krebs cycle
Catalyses the reaction of malate to alpha Oxaloacetate, which simultaneously produces 1 NADH from NAD+ and restarts the TCA cycle
What is the TCA cycle on reliant on in order to supply the ETC with MADH, FADH2 and ATP
ADP, FAD and NAD+
What is another use of citrate despite the TCA cycle
Cholesterol and FA synthesis
What is another use of alpha ketogluterate despite the TCA cycle
DNA and protein synthesis
What is another use of succinate despite the TCA cycle
Porphyrins e.g. haem
What is another use of malate despite the TCA cycle
Gluconeogenesis
What is another use of Oxaloacetate despite the TCA cycle
DNA and protein synthesis
