Respiration.

Question 1

What are the 4 stages of aerobic respiration?

Answer 1

• Glycolysis
• Link reaction
• Krebs cycle
• Oxidative phosphorylation

Question 2

What are the three stages of glycolysis?

Answer 2

• Phosphorylation
• Splitting of hexose i phosphate
• Oxidation of triose phosphate to pyruvate.

Question 3

Explain glycolysis.

Answer 3

• Two molecules of ATP are hydrolysed and release phosphate groups (one each)
• The Pi groups are added onto the glucose molecules to create hexose biphosphate (a 6c molecule)
• The hexose biphosphate is split into two triose PHOSPHATE (3c) molecules
• Triose phosphate is dehydrogenated, dehydrogenase enzymes alongside NAD (a coenzyme) remove hydrogens from triose phosphate.
• The two molecules of NAD (co-enzymes) accept the hydrogen atoms and become REDUCED (NADH)
• 2 molecules of NAD are reduced for every molecule of glucose undergoing the process. In addition, 4 molecules of ATP are made for every 2 triose phosphate molecules being oxidised.
• Oxidation of 2 molecules of triose phosphate produces 2 molecules of pyruvate.

Question 4

What are the products of glycolysis?

Answer 4

• 2 molecules of ATP (2 were used)
• 2 molecules of reduced NAD (NADH)
• 2 molecules of pyruvate

Question 5

What are the products of glycolysis?

Answer 5

• 2 molecules of ATP (2 were used)
• 2 molecules of reduced NAD (NADH)
• 2 molecules of pyruvate

Question 6

Where does glycolysis take place?

Answer 6

The cytoplasm

Question 7

Which stages of respiration occur only aerobically and which can occur anaerobically?

Answer 7

• Aerobic: Link reaction, Krebs cycle, Oxidative phosphorylation
• Anaerobic: only glycolysis can occur in anaerobic conditions, occurring in both aerobic and anaerobic.

Question 8

Where does the link reaction take place?

Answer 8

The mitochondrial matrix

Question 9

Explain the link reaction

Answer 9

• Pyruvate (3c) is decarboxylated (a carbon is removed from pyruvate) to form CO2 —> this converts pyruvate to a 2x molecule called acetate.
  Dehydrogenation also occurs as hydrogen is removed from pyruvate which is taken up by NAD to form NADH
• Acetate (2c) is combined with coenzyme A to form acetyl CoA.

Question 10

How often does the link reaction occur for every glucose molecule

Answer 10

2x

Question 11

Write the equation for the link reaction.

Answer 11

2 Pyruvate + 2NAD + 2CoA —> 2CO2 + 2NADH + 2 acetyl CoA

Question 12

Where does the krebs cycle occur?

Answer 12

In the mitochondrial matrix

Question 13

What happens in the krebs cycle?

Answer 13

• An acetyl group (2c) is released from acetyl CoA and combines with the 4c compound oxaloacetate to form a 6c compound called citrate
• Citrate is decarboxylated (looses a carbon) and produces a 5c compound, alongside one CO2 molecule and one molecule of NADH (reduced NAD)
• The 5c compound is further decarboxylated AND dehydrogenated - producing a 4c compound along with one CO2 molecule and one NADH.
• The 4c compound temporarily combines with, and is released from coenzyme A - substrate level phosphorylation occurs here which produces 1 ATP.
• The 4c compound is dehydrogenated, producing a different 4c compound and a molecule of FADH (reduced FAD)
• The 4c compounds atoms are rearranged, catalyzed by isomerase enzymes and then undergoes further dehydrogenation. This regenerates oxaloacetate and the cycle continues.

Question 14

In short, what is oxidative phosphorylation?

Answer 14

The production of ATP in the presence of oxygen

Question 15

What is produced by the Krebs cycle?

Answer 15

• 6 NADH
• 2 FADH
• 4 CO2
• 2 ATP

Question 16

Where are electron transport chains found?

Answer 16

Embedded in the inner mitochondrial membranes (cristae)

Question 17

What is chemiosmosis?

Answer 17

The flow of protons, down their concentration gradient across a membrane - through a channel associated with ATP synthase.

Question 18

Why is folded cristae advantageous for oxidative phosphorylation?

Answer 18

• Folded cristae give a large surface area for the electron carrier proteins and ATP synthase enzymes.