The Krebs cycle

Question 1

Where does the Krebs cycle take place?

Answer 1

• in the mitochondrial matrix

Question 2

What does each turn of the cycle result in?

Answer 2

• break down of an acetyl group
  
  • all that remains of the glucose that entered glycolysis
• reduced NAD and reduced FAD (flavin adenine dinucleotide) to be produed

Question 3

What happens to the Acetyl CoA initially?

Answer 3

• Acetyl CoA delivers an acetyl group to the Krebs cycle
• the 2C acetyl group combines w 4C oxaloacetate to form 6C citrate

Question 4

What happens to the citrate produced?

Answer 4

• citrate undergoes decarboxylation and dehydrogenation, producing one reduced NAD and carbon dioxide
• a 5C compound is formed

Question 5

What happens to the 5C compound?

Answer 5

• undergoes further decarboxylation and dehydrogenation reaction
• eventaually regenerating oxalocetate
  
  • and so the cycle continues
• more CO2, two more reduced NAD and one reduced FAD are produced
• ATP produced by substrate-level phosphorylation

Question 6

What is the net gain of products in the Krebs cycle?

Answer 6

• 3 reduced NADs
• 1 reduced fAD
• ATP

Question 7

What are the function of coenzymes?

Answer 7

• respiration is multi-step reaction pathway
• coenzymes are required to transfer ptrotons, electrons, and functional groups between many of these enzyme-catylsed reactions
• Redox reactions are important, many enzymes would be unable to function without coenzymes

Question 8

What are the differences between NAD and FAD?

Answer 8

• NAD takes part in all stages of cellular respiration
  
  • FAD only accepts hydrogen atom in the krebs cycle
• NAD accepts one hydrogen atom
  
  • FAD accepts 2
• reduced NAD is oxidised at the start of the electron transport chain releasing protons and electrons,
  
  • FAD oxidised further along the chain
• reduced NAD results in the synthesis of three ATP molc but reduced FAD results in synthesis as 2