Cellular Respiration

Question 1

Glycolysis

Answer 1

The breakdown of glucose to make pyruvate (3C) which is then used in the link reaction for Krebs cycle. Synthesises ATP

Question 2

Steps in glycolysis

Answer 2

1. Phosphorylation
2. Lysis
3. Oxidation
4. ATP formation

Question 3

Why are 2 ATP needed in phosphorylation?

Answer 3

It is needed to breakdown hexose sugar to hexose bisphosphate

Question 4

Lysis (breaking down) steps

Answer 4

Breaks down 6C (1,6 bisphosphate) compound to 3C compound (triose phosphate). The 3C then stabilises into glycerate-3-phosphate

Question 5

What is being oxidised in glycolysis?

Answer 5

The 3C compound sugar is being oxidised by removing the hydrogen atoms and donating it to NAD+ to make it into NADH

Question 6

How is ATP synthesised in glycolysis?

Answer 6

The sugar intermediates from the 3C compound releases energy to make ADP become ATP

Question 7

Where does the pyruvate moves to after glycolysis?

Answer 7

The pyruvate goes from the cytosol to the mitochondrial matrix through using carrier proteins

Question 7

Link reaction

Answer 7

Decarboxylates pyruvate
2 hydrogen is lost and is used to make NAD+ to NADH
The compound becomes an acetyl group which is then combined with coA to make acetyl coA

Question 8

TCA Cycle (Krebs cycle) purpose

Answer 8

Primarily used to make energy molecules such as NADH and ATP

Question 9

What is the first step in Krebs cycle?

Answer 9

Oxaloacetate combines with acetyl coA to make a 6C compound (citrate)

Question 10

How many times is the compound oxidised in Krebs cycle?

Answer 10

4 times, the last 2 times is when the 4C compound gives out hydrogen to reduce FAD and NAD

Question 11

What is the net product of Krebs cycle

Answer 11

In one cycle
2x CO2
1x ATP
1x FADH2
3x NADH

Question 12

Chemiosmosis

Answer 12

The action of maintaining the hydrogen ion gradient between the intermembrane space and mitochondrial matrix through using a transporter

Question 13

ETC (Electron transport chain)

Answer 13

High ATP production takes place through using the energy molecules made and chemiosmosis

Question 14

Steps in ETC:

Answer 14

1. FADH2 and NADH oxidises and releases hydrogen
2. Hydrogen breaks down to H+ + e-
3. H+ is carried to intermembrane space using a hydrogen pump that is powered by e-
4. e- is on an electron carrier that is used to give energy to other pumps as well
5. Hydrogen ion builds up in space and diffuses down towards ATP synthase where ADP + Pi => ATP

Question 15

What is the final acceptor of hydrogen in ETC?

Answer 15

oxygen. the end product is water

Question 16

What is the process of using the harnessed energy (through ETC) to synthesise ATP called?

Answer 16

Oxidative phosphorylation. Oxygen is reduced to create ATP

Question 17

Mitochondrial vs Photosynthetic ETC

Answer 17

Photosynthetic (Photophosphorylation) - Energy comes from light, powering delocalised electrons in photosystem 2 and 1
Mitochondrial - does not depend on light, depends on the presence of FADH2 and NADH from glucose

Question 18

What is the end product of light dependent reaction?

Answer 18

ATP, NADPH and O2

Question 19

Cyclic photophosphorylation

Answer 19

Does not involve reduction of NADP+ as there is not enough energy to do it
De-energized electron goes back to photosystem 1 (does not involve PS2)
Use it to conserve energy while still contributing to ATP synthesis

Question 20

Non-cyclic photophosphorylation

Answer 20

Involves both PS2 and PS1. Photolysis of water is done to supply delocalised electron and hydrogen. Supplies PS1 with excited electron to be able to make NADPH and ATP

Question 21

Alternative oxidase (AOX)

Answer 21

The protein that allows electron bypass ETC and combine with oxygen to water without giving energy to hydrogen pump

Question 22

Uncoupling protein (UCP)

Answer 22

Provides a pathway for hydrogen ions to diffuse down to the matrix without powering the ATP synthase. The energy is dissipated as heat

Question 23

Why do we need UCP and AOX?

Answer 23

To regulate ATP production

Question 24

How does UCP contribute to plant thermogenesis?

Answer 24

UCP gives out heat when hydrogen moves down the gradient which then the plant uses that heat their tissues

Question 25

How does thermogenesis (observing temperature) help measure the respiration rate of the plant

Answer 25

As oxygen is the final acceptor, the more oxygen is used due to AOX happening, it means that the plants respire more