Unit 5 - Respiration

Question 1

Site of Respiration

Answer 1

Mitochondria (mostly)

Question 2

Stages of Respiration

Answer 2

• Glycolysis
• Link Reaction
• Krebs Cycle
• Oxidative Phosphorylation

Question 3

Site of Glycolysis

Answer 3

Cytoplasm

Question 4

Glycolysis Process

Answer 4

• Glucose is phosphorylated by the hydrolysis of 2 ATP molecules to form glucose phosphate
• Glucose Phosphate is split into 2TP molecules
• TP is oxidised (a hydrogen is removed from each TP molecule) and the hydrogen is used to reduce NAD (forms NADH)
• TP is converted to pyruvate and 4ATP molecules are formed in the process (through substrate-level phosphorylation, TP donates its phosphate to ADP)
• Pyruvate is actively transported to mitochondrial matrix ONLY IF O₂ is present

Question 5

Products of Glycolysis (per 1 glucose molecule)

Answer 5

• Net gain of 2ATP
• 2 Pyruvate
• 2 NADH

Question 6

Why is Glycolysis Indirect Evidence of evolution?

Answer 6

• Glycolysis is a universal process that takes place in almost all living organisms
• Enzymes for this process are all located in the cytoplasm
• Glycolysis doesn’t require any organelles or membranes

Question 7

Site of the Link Reaction

Answer 7

Mitochondrial Matrix

Question 8

Link Reaction Process

Answer 8

• Pyruvate is decarboxylated (loses a CO₂ molecule)
• CO₂ diffuses out of the mitochondria as a waste product
• Pyruvate is oxidised and loses a hydrogens (accepted by NAD to form NADH) to form acetate (a 2C molecule)
• Acetate binds to coenzyme A to form acetylcoenzymeA

Question 9

Products of the Link Reaction (per 1 pyruvate molecule)

Answer 9

• 1 AcetylcoenzymeA
• 1 NADH
• 1 CO₂ (waste product)

Question 10

Site of the Krebs Cycle

Answer 10

Mitochondrial Matrix

Question 11

Krebs Cycle Process

Answer 11

• Acetyl (2C) is accepted by oxaloacetate (4C) from CoA to form citrate (6C)
• Citrate is decarboxylated and oxidised (NAD is reduced, forms NADH) to form a 5C molecule
• The 5C molecule is decarboxylated again and then oxidised 3 more times (2NADH and 1FADH₂ are formed from the reduction of 2NAD and 1FAD)
• ATP is also synthesised from ADP and P(i)

Question 12

Products of the Krebs Cycle (per 1 TURN)

Answer 12

• 1ATP
• 2CO₂
• 3NADH
• 1FADH₂
• HOWEVER the Krebs cycle turns 2X per 1 glucose molecule so if asked about this, double the products above

Question 13

Site of Oxidative Phosphorylation

Answer 13

Inner Mitochondrial Membrane

Question 14

Oxidative Phosphorylation Process

Answer 14

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