4 Metabolic Pathways And ATP Production II Flashcards
Q: How many reactions are in the krebs/ TCA cycle?
A: 8
Q: Where is acetyl CoA produced and by which enzyme?
A: mitochondria, pyruvate dehydrogenase complex
Q: What are the first 4 steps of the Krebs cycle?
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
Q: What are the last 4 steps of the Krebs cycle?
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
Q: What catalyses the reaction between ADP and GTP (reversible)?
A: nucleoside diphosphokinase
Q: What does one turn of the TCA cycle produce?
A: 3 NADH, 1 GTP, 1 FADH2, 2 CO2
Q: Why is the Krebs cycle aerobic?
A: NAD+ and FAD needed are only regenerated via the transfer of electrons to oxygen during oxidative phosphorylation
Q: Where do the TCA cycle enzymes reside?
A: mitochondrial matrix space since all proteins involved are soluble except succinate dehydrogenase- inner mito membrane
Q: During oxidative phosphorylation, how many ATP do reducer cofactors yield?
NADH
FADH2
A: 3, 2
Q: How many ATP does the oxidation of 1 acetyl CoA produce?
A: 12
Q: What is the theoretical maximum yield of ATP from the aerobic oxidation of 1 glucose?
A: 38
Q: What is the high energy linkage between acetate and CoA?
A: thioester
Q: Draw the Krebs cycle diagram.
A: Diagram
Q: In terms of protein metabolism, how is the amino acid alanine converted into acetyl CoA?
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
Q: What is the general degradation of amino acids?
A: aa group is removed and eventually excreted as urea
Carbon skeleton either goes into glucose production or def into Krebs cycle
Q: What is the use of glycerol-phosphate and malate-asparate shuttles?
A: transfer NADH (more accurately, high energy electrons of NADH) across the cytosol into matrix of mitochondria
Q: Which shuttles allow the transport of NADH (electrons of) across the cytosol into the mitochondrial matrix?
A: malate-aspartate
Glycerol phosphate
Q: Which cells have the glycerol phosphate shuttle?
A: skeletal muscle and brain
Q: Which cells have the malate-aspartate shuttle?
A: liver, kidney, heart
Q: Draw a diagram and explain the glycerol phosphate shuttle?
A: (Electrons are transferred rather than NADH itself)
- 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
- 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
Q: Draw a diagram and explain the malate-aspartate shuttle. Transamination involved?
A: Regeneration of cytosolic NAD+ = glycolysis: glucose -> pyruvate
NAD+ in and NADH + H+ out
- 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
- 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
Q: Catabolic or anabolic reactions?
NADPH
NADH
A: anabolic (building), catabolic (breakdown)
Q: What is the collective of a H+ (proton) and 2 electrons known as?
A: H-
Q: What is reductive biosynthesis?
A: anabolic pathways that require hydride ions (H-)
Q: What are two examples of the use of NADPH in reductive biosynthesis?
A: cofactor involved in thymidine synthesis
Cofactor involved in biosynthesis of cholesterol
Q: How does NADH assist as a cofactor in th biosynthesis of cholesterol?
A: catalyses the final reaction
C=C bond is reduced by transfer of a hydride ion (H-)
