Metabolic Pathways and ATP Production 1 Flashcards Preview

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Flashcards in Metabolic Pathways and ATP Production 1 Deck (42):

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)


What happens in lactic acid generation? Include any enzymes involved

Occurs in anaerobic conditions
Pyruvate --> Lactate (lactate dehydrogenase)
Reversible reaction


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)


What is the name for the metabolism process of fatty acids?



What is the name for fatty acid biosynthesis?



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 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



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


What are the net products of the TCA cycle?

2x CO2
1x FADH2
1x GTP


Why are the glycerol-phosphate and malate-aspartate shuttles required?

NAD+ regeneration


Where do the glycerol-phosphate and malate-aspartate shuttles operate?

Glycerol-phosphate - Skeletal muscle, brain
Malate-aspartate - Liver, kidney, and heart


Summarise the process of the glycerol-phosphate shuttle

1) Dihydroxyacetone (DHAP) -> Glycerol 3-phosphate (G3P), takes place in cytosol. Generates NAD+
2) G3P enters mitochondrial matrix
3) G3P -> DHAP (generates FADH2 which donates H2 to coenzyme Q as part of ox.phosphorylation)
4) DHAP passes back out into cytosol, cycle repeats.


Summarise the process of the malate-aspartate shuttle

- Uses two membrane transporters
- alpha-ketoglutarate transporter - exchanges alpha-ketoglutarate for malate.
- glutamate-aspartate transporter - exchanges glutamate for aspartate.
1) Oxaloacetate -> Malate (cytosol, malate dehydrogenase, NAD+ generated in cytosol)
2) Malate exchanged in alpha-ketoglutarate transporter into mitochondrial matrix
3) Malate transformed back into oxaloacetate by mitochondrial malate dehydrogenase generating NADH.
4) Transamination occurs, glutamate + oxaloacetate -> alpha-ketoglutarate + aspartate.
5) a-KG into Malate/alpha-KG transporter, aspartate into Glutamate, aspartate transporter.
Cycle continues


What is the electron transport chain?

A chain of three protein complexes and two mobile carriers which act as electron carriers


List the 3 protein complexes in the electron transport chain

1) NADH dehydrogenase complex
2) Cytochrome b-c1 complex
3) Cytochrome oxidase complex


What are the two mobile carriers in the electron transport chain?

1) Ubiquinone (a.k.a. co-enzyme Q) - carries electrons between protein complexes 1 and 2.
2) Cytochrome C - carries electrons between protein complexes 2 and 3.


What is the function of the electron transport chain and how does it accomplish this?

Pumping of protons into the inter membrane space. Each protein accepts electrons, as the electrons pass through the complexes, a proton is passed or "pumped" into the intermembrane space.


Explain the chemiosmotic model

Protons are moved into intermembrane space by energy generated from electron transport chain. The pumped protons move back down their electrochemical gradient through a specific channel, coupled to an enzyme called ATP synthase. The movement of the protons through the channel generates the energy to synthesise ATP.


Summarise the structure of ATP and it uses and synthesise ATP

- Multimeric enzyme
- Has a membrane-bound part and F1 part projecting into matrix.
- When protons are flowing into the mitochondrial matrix - ATP synthesis takes place.
- When protons are flowing into intermembrane space - ATP is being used.


List metabolic poisons

Cyanide (CN-)
Azide (N3-)
Carbon Monoxide (CO)


Explain cyanide's toxicity

Binds with high affinity to ferric (fe3+) form of haem group in cytochrome oxidase complex and blocks flow of electrons through transport chain.


Explain azide's toxicity

Bind with high affinity to ferric (fe3+) form of haem group in cytochrome oxidase complex and blocks flow of electrons through electron transport chain.


Explain carbon monoxide's toxicity

Binds to ferrous (fe2+) form of haem group in cytochrome oxidase complex, blocks flow of electrons through transport chain.


Explain malonate's toxicity

Closely resembles succinate
Competitive inhibitor of succinate dehydrogenase
Slows flow of electrons from succinate to ubiquinone so fewer electrons being passed into electron transport chain.


Explain oligomycin's toxicity

Inhibits oxidative phosphorylation
Binds to stalk of ATP synthase, blocking flow of electrons through the enzyme - ATP synthesis inhibited.


Explain Dinitrophenol's toxicity

Transports H+ across mitochondrial membrane before they reach ATP synthase channel - therefore uncouples ox. phosphorylation from ATP production.