Respiration (BIOL4)

Question 0

Where does glycolysis take place?

Answer 0

The cytoplasm of cells

Question 1

What is the order of the stages in aerobic respiration?

Answer 1

1. Glycolysis

2. Link reaction

3. Krebs cycle

4. Oxidative phosphorylation

Question 2

What happens during glycolysis?

Answer 2

1. 2 ATP used to add 2 phosphate to glucose –> 2x TP and 2x ADP
2. TP oxidised –> 2x pyruvate
3. NAD collects H+ –> NADH
4. 4 ATP made, but 2 used –> net gain of 2 ATP

Question 3

Where does the link reaction take place?

Answer 3

The matrix of mitochondria

Question 4

What happens during the link reaction?

Answer 4

1. 2 pyruvate enter matrix
2. Pyruvate decarboxylated - 1C removed as CO2
3. Pyruvate oxidised removing H, forms NADH; pyruvate –> acetate
4. Acetate + CoA –> acetylCoA
5. No ATP formed during link reaction!

• Link reaction occurs twice for every glucose molecule: 2CO2 and 2NADH made

Question 5

Where does the Krebs cycle take place?

Answer 5

Matrix of mitochondria

Question 6

What happens during the Krebs cycle?

Answer 6

1. AcetylCoA + oxaloacetate –> citrate
   
   • ​​CoA returns to link reaction to be used again
2. 6C citrate converted into 5C molecule; decarboxylated and dehydrogenated to remove CO2 and H
   
   • ​​​​​H + NAD –> NADH
3. Decarboxylation and dehydrogenation of 5C –> 4C producing 1 FADH and 2 NADH;
   
   • ATP made by direct transfer of P from immediate compound to ADP (substrate-level phosphorylation)
4. Citrate converted into oxaloacetate to be used again

Question 7

Where does oxidative phosphorylation take place?

Answer 7

Inner membrane of the mitochondria

Question 8

What happens during oxidative phosphorylation?

Answer 8

1. NADH and FADH oxidised to NAD and FAD, release H atoms and split into protons and electrons
2. Electrons move along ETC, losing energy at each carrier
3. Energy used by electron carried to pump protons from mitochondrial matrix into inter membrane space
4. Conc. of protons h. in inter membrane space than matrix; forms electrochemical gradient
5. Protons move down electrochemical gradient back into matrix via ATP synthase
   
   • ​​movement drives synthesis of ATP (ADP + Pi)
6. Chemiosmosis - movement of protons across membrane which generates ATP
7. In matrix, at end of ETC, protons, electrons and oxygen (from blood) combine to form H2O
   
   • ​​oxygen final electron acceptor!

Question 9

How many molecules are made from one glucose molecule?

Answer 9

32 ATP made from one glucose molecule

NADH = 2.5 ATP

FADH = 1.5 ATP

Question 10

What is formed during anaerobic respiration in animals?

Answer 10

Lactate fermentation:

Pyruvate –> lactate

NADH –> NAD

Question 11

What is formed during anaerobic respiration in plants?

Answer 11

Alcoholic fermentation:

Pyruvate –> ethanal –> ethanol

CO2 removed to form ethanal

NADH –> NAD to form ethanol