Catabolism of Pyruvate Flashcards
Importance of the need to regenerate NAD+
- Only limited amounts of NAD+ are present in cell
- Glycolysis reduces NAD+ to NADH + H+
- NADH must be re-oxidised to let glycolysis continue
NAD+ is regenerated through what process
The oxidative metabolism of pyruvate
Stage 1 in Aerobic Metabolism (oxidation) of pyruvate
Citric Acid Cycle
- Pyruvate enters the mitochondria matrix
- Converted to acetyl-coA (catalysed by Pyruvate Dehydrogenase Complex PDC)
Stage 2 in Aerobic Metabolism (oxidation) of pyruvate
Krebs Cycle
- Acetyl-coA condenses with 4C compound to form 6C compound
- 6C compound decarboxylated twice (yields CO2)
- 4 oxidation reactions (yield NADH + H+ and FADH2)
Stage 3 in Anaerobic Metabolism (oxidation) of pyruvate
Tricarboxylic Acid (TCA) Cycle
- GTP (nucelotide) is formed
- 4C compound recreated
All enzymes of the TCA cycle are located in the matrix apart from succinate dehydrogenase (located in inner mitochondrial membrane
How many pairs of electrons are transferred in the conversion of NAD+ to NADH + H+ ?
3 pairs
How many pairs of electrons are needed to reduce FAD to FADH2 ?
1 pair
Where does the TCA cycle occur?
In the mitochondria
ANAEROBIC fate of pyruvate
alcoholic fermentation, lactic acid formation in humans
AEROBIC fate of pyruvate
further oxidised in the citric acid cycle
What are the structural features of the mitochondria?
- Inner membrane (proteins)
- Outer membrane
- Central matrix (containing enzyme of TCA cycle)
- Cristae folds
From each acetyl-coA, TCA cycle generates…
- 3 NADH + H+
- 1 FADH2
- 1 GTP
- 2 CO2
How is pyruvate metabolised to Acetyl-CoA
PDC catalyses the oxidative decarboxylation of pyruvate to acetyl-CoA
Irreversible reaction
What is PDC?
Pyruvate Dehydrogenase Complex
- consists of 3 enzymes
- allosterically regulated by phosphorylation
- PDC activity determines glucose oxidation in well oxygenated tissues
How many reactions in total are in the TCA cycle?
8 reactions
TCA Cycle Overview
two carbon unit from acetyl-CoA condenses with a four-carbon unit
- Resulting six-carbon unit is decarboxylated twice forming CO2
- Four oxidation recations occur forming NADH + H+ and FADH2
- One GTP is formed (energy)
- Four carbon unit is recreated
Each turn of the TCA cycle involves the uptake of two ______ atoms in the form of _________ and release of two _______ as ____
- carbon atoms
- acetyl-CoA
- carbon atoms
- CO2
High ATP, NADH and acetyl-CoA means _____ energy
high
High ADP and NAD+ means _____ energy
low
High succinyl-CoA and acetyl-CoA means…
Plenty of precursor molecules for biosynthetic reactions
All of the enzymes of the TCA cycle are associated with what structure?
Mitochondria
