21 - Citric Acid Cycle Flashcards
What is the final part of the oxidation of nutrients to CO2?
The citric acid cycle
True or false? All nutrients can somehow be broken down to acetyl-CoA?
True
The citric acid cycle oxidizes acetyl-CoA to _____ and reduces NAD+ and FAD to _____ and ____
Acetyl-CoA oxidized to CO2
NAD and FAD reduced to NADH and FADH2
What fuels aerobic ATP generation?
The energy from the electron chain oxidizing NADH and FADH2 (they donate their electrons to the ETC), reducing oxygen to water.
What is the equation for oxidative phosphorylation?
O2 + NADH + H+ -> H2O + NAD+
True or false? The conversion of nutrients (fatty acids, glycerol, glucose, amino acids) to pyruvate and/or Acetyl-CoA is reversible?
True
What three types of nutrients can make pyruvate (which can then be made into Acetyl-CoA)?
Glycerol, glucose and amino acids
Which two enzymes can be made directly into Acetyl-CoA?
Fatty acids and amino acids
Where does the citric acid cycle take place?
mitochondria
Why does the citric acid cycle not take place in red blood cells?
They don’t have mitochondria, which is where the TCA takes place
True or false? ALL metabolites needed for the citric acid cycle must be imported into the mitochondria?
True
What does a more positive E° (standard reduction potential) indicate?
Higher affinity for electrons
With regards to E°, when is a reaction involving half reactions spontaneous?
When the half reactions add to make a positive E°
The a full reaction (with a combinatino of half reactions), in what direction to electrons flow (with regards to E°)?
Flow spontaneously from the species with more negative E° to more positive E°
The positive partner is reduced
The negative partner reduces the positive partner
What are the two redox coenzymes that are forms of nicotinic acid?
Nicotinamide adenine dinucleotide (NADH)
Nicotinamide adenine dinucleotide phosphate (NADPH)
What are the two coenzymes that are forms of riboflavin (vitamin B2)? (Flavin coenzymes)
Flavin mononucleotide (FMN)
Flavin adenine dinucleotide (FAD) - tightly bound in flavoproteins
What is the number of carbon atoms in the reaction intermediates of TCA, starting at the condensation of acetyl CoA and oxaloacetate? What products coe out with each oxidative decarboxylation?
C4 (oxaloacetate) + C2 (Acetyl CoA) = C6 = C5 + NADH + CO2 = C4 + NADH + CO2 = C4 (oxaloacetate) + ATP + FADH2 + NADH
What enzyme converts pyruvate to acetyl CoA?
Pyruvate dehydrogenase
(TCA cycle) What enzyme converts acetyl CoA to citrate? What is required?
Citrate synthase, oxaloacetate is required to start the reaction.
(TCA cycle) What enzyme converts citrate to isocitrate?
Aconitase
(TCA cycle) True or false? Redox reactions always require to half reactions.
True, one to be reduced and one to be oxidized
(TCA cycle) What reaction starts the citric acid cycle?
C2 (Acetyl-CoA) and C4 (Oxaloacetate)
How many times does the citric acid cycle run for one glucose?
Twice
Is the oxidation of pyruvate to acetyl-CoA reversible?
no
(TCA cycle) What enzyme converts isocitrate to α-ketoglutarate? What is required?
isocitrate dehydrogenase, NAD+ is reduced to NADH, forming CO2 in the process
(TCA cycle) What enzyme converts α-ketoglutarate to Succinyl-CoA? What is required?
Ketoglutarate dehydrogenase, NAD+ is reduced to NADH and CO2 is produced
(TCA cycle) What enzyme converts Succinyl-CoA to Succinate? What is required?
Succinyl-CoA synthetase, ADP is phosphorylated to ATP
(TCA cycle) What enzyme converts succinate to fumarate? What is required?
Succinate dehydrogenase, FAD is reduced to FADH2
(TCA cycle) What enzyme converts fumarate to malate?
Fumarase
(TCA cycle) What enzyme converts malate to oxaloacetate? What is required?
Malate dehydrogenase, NAD+ is reduced to NADH
What are the six requirements for the oxidation of pyruvate to acetyl CoA (excluding pyruvate itself)?
Pyruvate dehydrogenase NAD+ FAD TPP Coenzme A (CoA-SH) Lipoic acid
What is NAD+ derived from?
Niacin (vitamin B3)
What is TPP (thiamine pyrophosphate) derived from?
thiamine (vitamin B1)
What is FAD derived from?
Riboflavin (vitamin B2)
What is Coenzyme A (CoA-SH) derived form?
pantothenic acid (vitamin B5)