Respiration

Question 1

What are the four stages of aerobic respiration?

Answer 1

1. Glycolysis
2. Link reaction
3. Kreb cycle
4. Electron transport chain

Question 2

What are the main steps in glycolysis?

Answer 2

**Phosphorylation **
1. Glucose is phosphorylated by adding a phosphate froma molecule of ATP.
1. This creates one molecule of hexose phosphate and a molecule of ADP.
1. Hexose phosphate is phosphorylated by ATp to form hexose biphosphate and another molecule of ADP.
1. Hexose biphosphate is split up into 2 molecuels of triose phosphate
Oxidation
1. Triose phosphate is oxidised, forming 2 molecules of pyruvate.
1. NAD collects the hydrogen ions, forming 2 NADH.
1. 4 ATP are produced, but 2 were used up in stage one, so there’s a net gain of 2 ATP.

Question 3

What are the main steps in the link reaction?

Answer 3

1. Pyruvate is actively transported into the matrix of mitochondria.
2. Pyruvate is decarboxylated, one carbon atom is removed from pyruvate in the form of CO2
3. NAD is reduced to NADH - it collects hydrogen from pyruvate, changing pyruvate into acetate.
4. Acetate is combined with coenzyme A to form acetyl CoA
5. No ATP is produced

Question 4

What are the main steps in the kreb cycle?

Answer 4

1. The acetyl group from acetyl CoA combines with oxaloacetate to form citrate.
2. This is catalysed by citrate synthase. COenzyme A goes back to the link reaction to be used again
3. The 6C citrate molecule is converted to a 5C molecule.
4. Decarboxylation occurs, where carbon dioxide is removed.
5. Dehydrogenation also occurs, the hydrogen is used to produce NADH from NAD
6. The 5C molecule is converted to oxaloacetate. Decarboxylation and dehydrogenase occur, producing one FADH2 and two NADH.
7. One ATP is produced by substrate-level phosphorylation.

Question 5

What are the main steps in oxidative phosphorylation?

Answer 5

1. Hydrogen atoms are released from NADH and FADH2. The hydrogen atom aplit into protons and electrons
2. The electrons move along the electron transport chain, losing energy at each carrier. The ETC is located in the inner mitochondrial membrane. This membrane is folded into cristae, which increases the membrane’s surface area to maximise respiration
3. This energy is used by the electron carriers to pump protons from the mitochondial matric into the intermembrane space
4. The conc of protons is now higher in the intermembrane space than in the mitochondial matrix - this forms an electrochemical gradient
5. Protons move down the electrochemical gradient, back into the mitochondiral matrix, via the ATP synthase
6. This movement drives the synthesis of ATP from ADP and inorganic phosphate. This process of ATP production driven by the movement of H+ ions across a membrane is called chemiosmosis
7. In the mitochondrial matrix, at the end of the ETC, the protons, electrons and oxygen combine to form water. Oxygen is said to be the final electron acceptor

Question 6

How many ATP is produced during oxidative phosphorylation in total?

Answer 6

32

Question 7

How does lactate fermentation occur?

Answer 7

1. NADH transfer hydrogen to pyruvate to form lactate and NAD
2. NAD can be reused in glycolysis

Question 8

How does alcoholic fermentation occur?

Answer 8

CO2 is removed from pyruvate to form ethanal
NADH transfer hydrogen to ethanal to form ethanol and NAD
NAD can then be reused in glycolysis

Question 9

What is a respiratory substrate?

Answer 9

Any biological molecule that can be broken down in respiration to release energy

Question 10

What detemine the energy value of each substrate?

Answer 10

Hydrogen atoms per unit of mass
Lipids contain the most hydrogen atoms per unit of mass, followed by protein and carbohydrates

Question 11

What is respiratory quotient?

Answer 11

Volume or molecule of CO2 released/ Volume or molecuel of O2 consumed

Question 12

What are the RQ for lipids, proteins, and carbohydrates?

Answer 12

Lipids 0.7
Proteins 0.9
Carbohydrates 1

Question 13

What does it means when RQ is between 0.7 and 1.0 in human?

Answer 13

Some fats and carbohydrates are being used?

Question 14

What does it mean when RQ is above 1?

Answer 14

An organism is short of oxygen, and is having to respire anaerobically as well as aerobically

Question 15

Why do plants have low RQ sometimes?

Answer 15

CO2 released is used for photosynthesis