Respiration

Question 1

What does glycolysis make?

Answer 1

Pyruvate from glucose

Question 2

Describe glycolysis

Answer 2

Phosphorylation

1. Glucose is phosphorylated using a phosphate from a molecule of ATP, creating 1 molecule of glucose phosphate and 1 molecule of ADP
2. ATP is then used to add another phosphate, forming hexose bisphosphate
3. hexose bisphosphate is then split into 2 molecules of triose phosphate

Oxidation

1. Triose phosphate is oxidised (loses hydrogen), forming 2 molecules of pyruvate
2. NAD collects the hydrogen ions, forming 2 reduced NAD
3. 4 ATP are produced, but 2 were used up during phosphorylation, so there’s a net gain of 2 ATP

Question 3

Where does glycolysis take place?

Answer 3

Cytoplasm of cells

Question 4

In anaerobic respiration (in plants and yeast) what is pyruvate converted into?

Answer 4

Pyruvate —> Ethanal —-> Ethanol

Question 5

In anaerobic respiration (in animal cells and some bacteria) what is pyruvate converted to?

Answer 5

Pyruvate —> Lactate (lactic acid)

Question 6

Describe what happens during the link reaction

Answer 6

1. Pyruvate is decarboxylated (1 carbon atom is removed from pyruvate in the form of CO2)
2. Pyruvate is oxidised to form acetate and NAD is reduced to form reduced NAD
3. Acetate is combined with coenzyme A (CoA) to form acetyl coenzyme A (acetyl CoA)
4. No ATP is produced in this reaction

Question 7

Where does the link reaction take place?

Answer 7

Matrix of mitochondria

Question 8

How many times does the link reaction occur for 1 glucose molecule?

Answer 8

2

Question 9

Describe 3 things that happen from the link reaction for 1 glucose molecule

Answer 9

1. 2 molecules of acetyl CoA go into the Krebs cycle
2. 2 CO2 molecules are released as a waste product of respiration
3. 2 molecules of reduced NAD are formed and go to the last stage (oxidative phosphorylation)

Question 10

What does the Krebs cycle involve?

Answer 10

A series of oxidation-reduction reactions

Question 11

Where does the Krebs cycle take place?

Answer 11

Matrix of mitochondria

Question 12

How many times does the Krebs cycle happen for each pyruvate molecule?

Answer 12

1

Question 13

How many times does the Krebs cycle happen for each glucose molecule?

Answer 13

2

Question 14

Describe the Krebs cycle

Answer 14

1. Acetyl CoA from the link reaction combines with a 4C molecule (oxaloacetate) to form a 6C compound (citrate)

Coenzyme A goes back to the link reaction to be used again

2. The 6C citrate molecule is converted to a 5C molecule

Decarboxylation occurs, where CO2 is removed

Dehydrogenation also occurs, where hydrogen is removed

The hydrogen is used to produce reduced NAD from NAD

3. The 5C molecule is then converted to a 4C molecule

Decarboxylation and dehydrogenation occur, producing 1 molecule of reduced FAD and 2 molecules of reduced NAD

ATP is produced by the direct transfer of a phosphate group from an intermediate compound to ADP. When a phosphate is directly transferred from 1 molecule to another it’s called substrate-level phosphorylation. Citrate has now been converted into oxaloacetate