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Why are coenzymes needed in respiration?
To help enzymes carry out oxidation reactions in respiration.
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What is NAD
An organic, non-protein molecule that helps dehydrogenase enzymes to carry out oxidation reactions.
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How is NAD reduced?
When an NAD molecule has accepted 2 hydrogen atoms with their electrons, it is reduced.
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How is NAD oxidised?
When it loses electrons.
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When does NAD operate?
During Glycolysis, the Link reaction, the Krebs cycle and during the anaerobic ethanol and lactate pathways.
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What is the function of Coenzyme A?
To carry ethanoate (acetate) groups made from pyruvate during the Link reaction to the Krebs cycle.
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What can Coenzyme A also carry?
Acetate groups that have been made from fatty acids or from some amino acids onto the Krebs cycle.
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Where does glycolysis take place?
In the cell cytoplasm
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What does glycolysis involve/convert
Conversion of 1 molecule of glucose to 2 molecule of pyruvate.
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1st step of glycolysis
Glucose --> Glucose-6-phosphate. Phosphorylation. Glucose is activated.
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2nd step of glycolysis
Glucose-6-phosphate --> Fructose-6-phosphate. Isomerisation. 1 ATP used up.
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3rd step
Fructose-6-phosphate --> Fructose-1,6-diphosphate. Phosphorylation. 1 ATP used up. Fructose-1,6-diphosphate unstable+unreactive. Hexose bisphophate split into 2 molecules.
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4th step
Fructose-1,6-diphosphate --> 2x Triose phosphate. Cleavage. Fructose-1,6-diphosphate splits into 2x triose phosphate.
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5th step
2x Triose phosphate --> 2x phosphoglycerate. Oxidation occurs, involving removing 2 hydrogen atoms from each triose phosphate molecule. ATP formed.
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6th step
2x phosphoglycerate --> 2x pyruvate. ATP formed for each reaction. Hydrogen atom pairs accepted by NAD.
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Gross and net production of ATP
Gross production = 4, net production = 2.
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Reduced NAD produced?
2NADH2 produced as NAD has gained hydrogen.
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Where does the link reaction take place?
Inside the fluid matrix of the mitochondrion
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What happens in the link reaction?
Pyruvic acid is converted to Acetyl CoA. Coenzyme A is recycled.
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What is produced in the link reaction?
2 hydrogen atoms, carbon dioxide and NADH2.
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Where does the Krebs cycle take place?
In the fluid matrix of the mitochondrion.
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Stage 1 of Krebs Cycle
4C Oxaloacetic acid --> 6C Citric acid. 2C group of Acetyl CoA combines with 4C Oxaloacetic acid to form 6C Citric acid.
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2nd stage of Krebs Cycle
6C Citric acid --> 5C Keto Glutaric acid. 6C oxidised to 5C. Decarboxylation + dehydrogenation. Produces CO2, hydrogen and NADH2.
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3rd stage of Krebs Cycle
5C Keto Glutaric acid --> 4C Succinic acid. 5C oxidised to 4C. Generates CO2 and NADH2. Decarboxylation + dehydrogenation. 2 hydrogens produced, ATP produced by substrate-level phosphorylation.
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Stage 4 of Krebs cycle
4C Succinic acid --> 4C Malic acid. Oxidised. Hydrogen carrier = FAD. 2 hydrogens produced and FADH2.
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5th stage of Krebs cycle
4C Malic acid --> 4C Oxaloacetic acid. Cycle can start again. 2 hydrogens produced, NADH2 produced.
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What is produced during glycolysis?
2 ATP, 2 NADH2
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What is produced in the link reaction?
0 ATP, 2 NADH2, 2 CO2.
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What is produced during the Krebs Cycle?
2 ATP, 6 NADH2, 2 FADH2, 4 CO2.
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Card 2


What is NAD


An organic, non-protein molecule that helps dehydrogenase enzymes to carry out oxidation reactions.

Card 3


How is NAD reduced?


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Card 4


How is NAD oxidised?


Preview of the front of card 4

Card 5


When does NAD operate?


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