Metabolic Pathways and ATP Production 1 Flashcards
Sketch a cartoon of the 3 stages of cellular metabolism including cellular location
Check metabolism notes for diagram, cover and draw from memory, repeat when this card comes up
What are the 3 stages of cellular metabolism in order?
1) Glycolysis
2) TCA cycle
3) Oxidative phosphorylation
What is the effect of eating on metabolism?
Speeds it up
What is the effect of fasting on metabolism?
Slows it down
What are the steps involved in the first half of glycolysis? Include any enzymes involved
1) Glucose -> Glucose-6-P (ATP used) (hexokinase)
2) G-6-P -> Fructose-6-P (phosphoglucoisomerase)
3) F-6-P -> Fructose-1,6-bisphosphate (ATP used) (phosphofructokinase)
4) F-1,6-Bp -> Dihydroxyacetone phosphate (DHAP) + glyceraldehyde 3-phosphate (G-3-P) (aldolase)
5) DHAP -> G-3-P (triose phosphate isomerase)
Ends first half with two molecules of G3P
What are the steps involved in the second half of glycolysis? Include any enzymes involved
1) G3P -> 1,3 bisphosphoglycerate (NADH produced) (G3P dehydrogenase)
2) 1,3 bisphosphoglycerate -> 3-phosphoglycerate (generates ATP) (phosphoglycerate kinase)
3) 3-phosphoglycerate -> 2-phosphoglycerate (phosphoglycerate mutase)
4) 2-phosphoglycerate -> phosphoenolpyruvate (enolase)
5) Phosphoenolpyruvate -> pyruvate (generates ATP) (pyruvate kinase)
All of these steps occur twice for each molecule of glucose.
What is the net produce of glycolysis?
2 pyruvate, 2 ATP, 2 NADH
What are the 3 fates of pyruvate?
Alcoholic fermentation
Lactic acid generation
The Link Reaction
What happens in alcoholic fermentation?
Include any enzymes involved
Occurs in anaerobic conditions
Pyruvate –> Acetaldehyde (pyruvate decarboxylase)
Acetaldehyde –> ethanol (alcohol dehydrogenase)
NADH->NAD+
What happens in lactic acid generation? Include any enzymes involved
Occurs in anaerobic conditions
Pyruvate –> Lactate (lactate dehydrogenase)
Reversible reaction
NADH->NAD+
What happens in the link reaction? Include any enzymes involved
Occurs in mitochondrion, under aerobic conditions
Pyruvate + HS-CoA –> Acetyl CoA + CO2 (pyruvate dehydrogenase complex)
NAD+->NADH
What is the name for the metabolism process of fatty acids?
Beta-oxidation
What is the name for fatty acid biosynthesis?
Lipogenesis
Summarise the process of beta-oxidation
1) Fatty acid + HS-CoA + ATP –> Acyl CoA + AMP + PPi (two high energy bonds used) (occurs on the outer mitochondrial membrane)
2) Acyl CoA moved into mitochondrial matrix via carnitine shuttle.
3) Acyl CoA undergoes oxidation, hydration, oxidation again, then thiolysis. 1st oxidation = NADH produced. 2nd oxidation = FADH2 produced.
4) Shortened fatty acyl CoA and acetyl CoA produced. Fatty acyl CoA shortened by 2C every cycle apart from final cycle, 4C product produced.
5) Fatty acyl CoA starts cycle again. Acetyl CoA continues to krebs cycle.
State the net products of one cycle of beta-oxidation
1x Shortened fatty acyl CoA
1x Acetyl CoA
1x NADH
1x FADH2
State the locations of the steps of beta-oxidation
- Fatty acid to acyl CoA occurs on outer mitochondrial membrane
- Carnitine shuttle transfers across OMM
- All other steps occur in mitochondrial matrix
Summarise the process of lipogenesis
1) Acetyl CoA -> Malonyl CoA (acetyl CoA carboxylase)
2) Malonyl CoA -> Malonyl ACP (malonyl-CoA-ACP-transferase)
3) Acetyl CoA -> Acetyl ACP (acetyl-CoA-ACP-transferase)
4) Acetyl ACP + Malonyl ACP -> acetoacetyl-ACP (CO2 produced)(beta-ketoacyl ACP synthase)
5) Acetoacetyl-ACP -> D-3-hydroxyacyl-ACP (beta-ketoacyl ACP reductase)
6) D-3-hydroxyacyl-ACP -> Trans-2-enoyl ACP (3-hydroxyacyl ACP reductase)
7) Trans-2-enoyl ACP -> butryl ACP (enoyl ACP reductase).
Steps 4-7 cycle until desired elongation is complete or 16C chain is reached.
Give two examples of fatty acid metabolism disorders
- Medium-chain-acyl-coenzyme A dehydrogenase deficiency (MCADD)
- Primary carnitine deficiency
Summarise medium-chain-acyl-coenzyme A dehydrogenase deficiency
- Autosomal recessive disorder
- Fatal if undiagnosed
- Thought to account for 1/100 cases of sudden infant death syndrome
Summarise primary carnitine deficiency
- Autosomal recessive disorder
- Mutation in SLCC22A5 gene encoding carnitine transporter
- Results in reduced ability to uptake carnitine and as a result reduced beta-oxidation.
- Symptoms appear in infancy/early childhood as encephalopathies, cardiomyopathies, muscle weakness, hypoglycaemia.
Summarise how glucose can be converted to products for TCA cycle
Glycolysis
Summarise how amino acids can be converted into products for TCA cycle
Degradation of amino acids - Amino group removed from amino acid so carbon skeleton fed into glycolysis or TCA cycle.
Transamination - Amino group transferred from AA to a keto acid, new pair of amino and keto acids formed.
Summarise the TCA cycle
1) Oxaloacetate (4C) -> Citrate (6C) (citrate synthase)
2) Citrate (6C) -> Isocitrate (6C) (aconitase)
3) Isocitrate (6C) -> Alpha-ketoglutarate (5C) (CO2, NADH produced) (isocitrate dehydrogenase)
4) Alpha-ketoglutarate (5C) -> Succinyl-CoA (4C) (CO2, NADH produced) (alpha-ketoglutarate dehydrogenase complex)
5) Succinyl-CoA (4C) -> Succinate (4C) (GTP produced) (succinylcholine CoA synthetase)
6) Succinate (4C) -> Fumarate (4C) (succinate dehydrogenase, FADH2 produced)
7) Fumarate (4C) -> Malate (4C) (fumerase)
8) Malate (4C) -> (Oxaloacetate regenerated, NADH produced) (malate dehydrogenase)
Where does the TCA cycle take place?
Mitochondrial matrix
