Respiration

Question 1

What are the two stages of glycolysis?

Answer 1

1) Phosphorylation

2) Oxidation

Question 2

Describe the Phosphorylation stage of Glycolysis.

Answer 2

1) Glucose is phosphorylation using a phosphate from a molecule of ATP, creating 1 molecule of glucose phosphate and 1 of ADP
2) ATP is then used to add another phosphate, forming hexose biphosphate
3) Hexose biphosphate js then split into 2 molecules of triose phosphate

Question 3

Describe the oxidation stage of glycolysis.

Answer 3

1) Triose phosphate is oxidised, forming 2 molecules of pyruvate.
2) NAD collects the hydrogen ions, forming two reduced NAD (NADH)
3) 4 ATP are produced, but 2 were used up during phosphorylation, meaning two ATP are formed.

Question 4

Describe anaerobic respiration in mammals

Answer 4

Lactate fermentation. Pyruvate is reduced by NADH to form lactate/lactic acid + NAD

Question 5

Describe anaerobic respiration in plants.

Answer 5

Alcoholic fermentation. Pyruvate is decarboxylated to form ethanal, which is then reduced using NADH to form ethanol + NAD.

Question 6

What is the purpose of anaerobic respiration?

Answer 6

The production of lactate or ethanol regenerates oxidised NAD. This means glycolysis can continue even when there is g much oxygen around, so a small amount of ATP can be produced fo keep some biological processes working.

Question 7

Describe the link reaction.

Answer 7

• Pyruvate is decarboxylated, then Oxidised to form acetate and NAD is reduced to NADH.
• Acetate is combined with coenzyme A (CoA)to form acetylcoenzyme a
• No ATP is produced from this.

Question 8

What must we know about the link reaction?

Answer 8

• The link reaction occurs twice for every glucose molecule, meaning two acetylcoenzymeA go into the Krebs cycle.
• Two CO2 molecules are released as a waste product
• Two molecules of NADH are formed and go to oxidative phosphorylation

Question 9

Describe the Krebs cycle.

Answer 9

• Acetyl CoA combines with oxaloacetate (4C) to form citrate (6C)
• Coenzyme A goes back to the link reaction
• Citrate is converted to a 5C molecule, whilst decarboxylation and dehydrogenation occur, forming CO2 and NADH.
• The 5C is converted to oxaloacetate, reducing two molecules of NAD and one of FAD, and forming 1 ATP.

Question 10

What is formed from the link reaction (from 1 glucose)

Answer 10

• 2x Acetylcoenzyme A
• 2x Carbon dioxide
• 2x NADH

Question 11

What is formed from the Krebs cycle.

Answer 11

• 1x Coenzyme A
• 1x Oxaloacetate
• 2x Carbon dioxide
• 1x ATP
• 3x NADH
• 1x FADH

Question 12

Describe oxidative phosphorylation.

Answer 12

1) Hydrogen atoms are released from NADH and FADH as they’re oxidised. The H atoms split to protons and electrons
2) The electrons move down the electron transport chain (made up of electron carriers), losing energy at each carrier.
3) This energy is used by the carriers to pump protons from the mitochondrial matrix into the inter membrane space.
4) The concentration of protons is now higher in the intermembrane than in the matrix, forming an electrochemical gradient
5) Protons move down the electrochemical gradient via ATP synthase, forming ATP from ADP and Pi
6) This process of ATP synthesis from the movement of H+ is called chemiosmosis
7) In. The matrix, the protons, electrons and O2 (from blood) combine to form water.

Question 13

Describe the journey of an H+ during oxidative phosphorylation.

Answer 13

1) formed in the mitochondrial matrix from oxidising NADH+FADH
2) Electron carrier proteins
3) Inter membrane space
4) ATP synthase enzyme
5) Mitochondrial matrix, where they react with electrons and O2 to produce water.