Metabolic and ATP II Flashcards
How is pyruvate used to make Acetyl Co-A?
Pyruvate + HS-CoA —> Acetyl CoA + CO2
- Using enzyme pyruvate dehydrogenase complex and NAD+ is converted to NADH
- This reaction occurs in the mitochondrion. The acetyl CoA formed is committed to entry into the Krebs’ Cycle.
Structure of Acetyl Co-A
The Thioester bond is a high-energy linkage so it is readily hydrolysed enabling Acetyl CoA to donate acetate (2C) to other molecules.
What is produced in the Krebs cycle overall and therefore how many ATP are formed?
One turn produces: 3 x NADH 1 x GTP 1 x FADH2 2 x CO2
1 NADH = 3 ATP
1 FADH2= 2ATP
So 1 x acetyl coA =
(3xNADH) + (1 xFADH) + (1xGTP) =12 ATP
What is transamination?
Protein Metabolism involves transamination reactions - a reaction in which an amine group is transferred from one amino acid to a keto acid thereby forming a new pair of amino and keto acids.
Example of protein metabolism involving transamination (using alanine)
Alanine + a-ketoglutarate –> pyruvate + glutamate
- Alanine undergoes transamination by the action of enzyme Alanine Aminotransferase.
- Pyruvate can enter the TCA cycle.
- Glutamate is converted back to a-ketoglutarate by Glutamate Dehydrogenase. This generates NH4+ which is ultimately converted to urea.
How and why is NADH transported?
NADH produced in glycolysis needs to enter the mitochondria to be used by the process of oxidative phosphorylation and to generate NAD+.
There is only a finite amount of NAD+ so unless it is regenerated glycolysis will stop.
Hence, NADH (or more accurately, the high energy electrons of NADH) cross the cytosol into the matrix of the mitochondrion by:
- Glycerol Phosphate Shuttle - skeletal muscle, brain
- Malate Aspartate Shuttle - liver, kidney, heart
How
How does the Malate-Aspartate shuttle work?
-Uses 2 membrane carriers and 4 enzymes
Hydrogen is transferred from cytoplasmic NADH to oxaloacetate to give malate, a reaction catalysed by cytosolic malate dehydrogenase (MDH). Malate is transported into the mitochondria where it is rapidly re-oxidised by NAD+ to give oxaloacetate and NADH (catalysed by mitochondrial MDH). Oxaloacetate and glutmate then undergo transamination to give the pair alpha-ketoglutarate and aspartate, which can exit the mitochondrial matrix via specific transporters in exchange for malate and glutamate respectively
2 antiporters (carrier proteins)
Malate alpha-ketoglutarate antiporter
Glutamate- aspartate antiporter.
Difference between NADPH and NADH
- NADPH takes part in anabolic reactions, whereas NADH takes place in catabolic reactions
- The use of different co-factors for different sets of reactions allows electron transport in catabolism to be kept separate to that of anabolism
What can GTP act as?
It can donate its phosphate group in protein synthesis or signal transduction.
When succinyl-CoA is converted to succinate, GTP is formed. Where in the body is ATP formed from the same reaction?
ATP: skeletal and cardiac muscle
GTP: liver, tissues that catalyse anabolic reactions
Where are most of the enzymes required for the TCA cycle found?
Any exceptions?
These are soluble protein found in the mitochondrial matrix space.
SUCCINATE DEHYDROGENASE is attached to the inner surface of the inner mitochondrial membrane.
What is the maximum theoretical yield of ATP following aerobic respiration of one molecule of glucose?
38
What is the process of degradation of amino acids?
Remove the amino acid whilst the carbon is either funnelled into the production of glucose or fed into the krebs cycle
What does degredation of all 20 amino acids produce?
Only 7 molecules:
- pyruvate
- acetyl coA
- acetoacetyl coA
- a-ketoglutarate
- succinyl coA
- fumarate
- oxaloacetate
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What does high levels of alanine aminotransferase a sign of?
-Hepatic disorders such as Hepatitis C.
