4 Metabolic Pathways And ATP Production II Flashcards

1
Q

Q: How many reactions are in the krebs/ TCA cycle?

A

A: 8

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2
Q

Q: Where is acetyl CoA produced and by which enzyme?

A

A: mitochondria, pyruvate dehydrogenase complex

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3
Q

Q: What are the first 4 steps of the Krebs cycle?

A

A: Oxaloacetate (4C) -> citrate (6C)
E: citrate synthase
Acetyl-CoA in and HS-CoA + H+ out
(Addition of acetyl group)

Citrate (6C) -> isocitrate (6C)
(((E: aconitase
(Isomerisation where hydroxyl group is moved))))

Isocitrate (6C) -> alpha-ketoglutarate (5C)
E: isocitrate dehydrogenase
NAD+ in and CO2 + H+ + NADH out

alpha-ketoglutarate (5C) -> succinyl-CoA (4C)
E: alpha-ketoglutarate dehydrogenase complex
NAD+ and HS-CoA in and CO2 + H+ + NADH out

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4
Q

Q: What are the last 4 steps of the Krebs cycle?

A

A: Succinyl-CoA (4C) -> succinate (4C)
E: succinyl CoA synthetase
GDP and Pi and H2O in and HS-CoA + GTP

succinate (4C) -> fumarate (4C)
E: succinate dehydrogenase
FAD in and FADH2 out

Fumarate (4C) -> malate (4C)
(((E: fumerase
Water in
Double bond is broken)))

Malate (4C) -> oxaloacetate (4C)
E: malate dehydrogenase
NAD+ in and H+ + NADH out

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5
Q

Q: What catalyses the reaction between ADP and GTP (reversible)?

A

A: nucleoside diphosphokinase

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6
Q

Q: What does one turn of the TCA cycle produce?

A

A: 3 NADH, 1 GTP, 1 FADH2, 2 CO2

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7
Q

Q: Why is the Krebs cycle aerobic?

A

A: NAD+ and FAD needed are only regenerated via the transfer of electrons to oxygen during oxidative phosphorylation

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8
Q

Q: Where do the TCA cycle enzymes reside?

A

A: mitochondrial matrix space since all proteins involved are soluble except succinate dehydrogenase- inner mito membrane

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9
Q

Q: During oxidative phosphorylation, how many ATP do reducer cofactors yield?

NADH

FADH2

A

A: 3, 2

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10
Q

Q: How many ATP does the oxidation of 1 acetyl CoA produce?

A

A: 12

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11
Q

Q: What is the theoretical maximum yield of ATP from the aerobic oxidation of 1 glucose?

A

A: 38

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12
Q

Q: What is the high energy linkage between acetate and CoA?

A

A: thioester

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13
Q

Q: Draw the Krebs cycle diagram.

A

A: Diagram

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14
Q

Q: In terms of protein metabolism, how is the amino acid alanine converted into acetyl CoA?

A

A: transamination of alanine by alanine aminotransferase to alpha-ketoglutarate

Results in pyruvate and glutamate. Pyruvate can enter TCA cycle.

Amine group transferred from amino acid to keto acid

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15
Q

Q: What is the general degradation of amino acids?

A

A: aa group is removed and eventually excreted as urea

Carbon skeleton either goes into glucose production or def into Krebs cycle

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16
Q

Q: What is the use of glycerol-phosphate and malate-asparate shuttles?

A

A: transfer NADH (more accurately, high energy electrons of NADH) across the cytosol into matrix of mitochondria

17
Q

Q: Which shuttles allow the transport of NADH (electrons of) across the cytosol into the mitochondrial matrix?

A

A: malate-aspartate

Glycerol phosphate

18
Q

Q: Which cells have the glycerol phosphate shuttle?

A

A: skeletal muscle and brain

19
Q

Q: Which cells have the malate-aspartate shuttle?

A

A: liver, kidney, heart

20
Q

Q: Draw a diagram and explain the glycerol phosphate shuttle?

A

A: (Electrons are transferred rather than NADH itself)

  1. Cytosolic glycerol-3-phosphate dehydrogenase transfers electrons to dihydroxyacetone phosphate to form glycerol 3-phosphate

dihydroxyacetone phosphate -> glycerol 3-phosphate
E: (cytosolic) glycerol-3-phosphate dehydrogenase
NADH + H+ in and NAD+ out

  1. Membrane form of same enzyme transfers electrons to FAD where then transferred to coE Q (part of electron transport chain)

Glycerol-3-phosphate -> dihydroxyacetone phosphate
E: (membrane bound) glycerol-3-phosphate dehydrogenase
E-FAD in and E-FADH2 out

E-FADH2 -> E-FAD
Q in and QH2 out

21
Q

Q: Draw a diagram and explain the malate-aspartate shuttle. Transamination involved?

A

A: Regeneration of cytosolic NAD+ = glycolysis: glucose -> pyruvate
NAD+ in and NADH + H+ out

  1. hydride ion (H-) is transferred from cytoplasmic NADH to oxaloacetate to give malate, catalysed by cytosolic malate dehydrogenase MDH

oxaloacetate -> malate
E: (cytosolic) malate dehydrogenase MDH
NADH (cytoplasmic) + H+ in and NAD+ out

  1. Malate is transported into mitochondria where it is rapidly re oxidised by NAD+ to give oxaloacetate and NADH, catalysed by mitochondrial MDH

malate -> oxaloacetate
E: (mitochondrial) malate dehydrogenase
NAD+ in and NADH + H+ out

A: malate into mito and alpha-ketoglutarate into cyto
B: glutamate into mito and aspartate into cyto

A: Transamination involved:
Glutamate + oxaloacetate-> alpha-ketoglutarate +aspartate

Transamination allows different compounds to pass through transporters

22
Q

Q: Catabolic or anabolic reactions?

NADPH
NADH

A

A: anabolic (building), catabolic (breakdown)

23
Q

Q: What is the collective of a H+ (proton) and 2 electrons known as?

A

A: H-

24
Q

Q: What is reductive biosynthesis?

A

A: anabolic pathways that require hydride ions (H-)

25
Q

Q: What are two examples of the use of NADPH in reductive biosynthesis?

A

A: cofactor involved in thymidine synthesis

Cofactor involved in biosynthesis of cholesterol

26
Q

Q: How does NADH assist as a cofactor in th biosynthesis of cholesterol?

A

A: catalyses the final reaction

C=C bond is reduced by transfer of a hydride ion (H-)