8.2 Cell respiration (HL)

Question 1

5 steps of respiration `

Answer 1

1. Glycolysis
2. Link reaction
3. Krebs cycle
4. Electron transport chain
5. Chemiosmosis

Question 2

Mitochondria: Function of outer membrane

Answer 2

Contains transport proteins that enable movement of pyruvate from cytosol

Question 3

Mitochondria: Function of inner membrane/cristae and how its adapted for efficiency

Answer 3

Contains ETC and ATP synthase. Inner membrane is folded which increases SA:V ratio for more available surface

Question 4

Mitochondria: Function of matrix

Answer 4

Central cavity that contains all the enzymes and suitable pH for Krebs cycle and link reaction

Question 5

Mitochondria: Function of DNA and ribosomes

Answer 5

Ribosomes synthesize proteins/enzymes for aerobic respiration while naked DNA maintains function

Question 6

Mitochondria: Inter-membrane space function and how its adapted for efficiency

Answer 6

Used to create hydrogen ion gradient upon proton accumulation. It has a small space between membrane to maximize gradient

Question 7

What is electron tomography?

Answer 7

A technique for obtaining 3D structures of sub-cellular structures using electron micrographs

Question 8

Electron carrier

Answer 8

A molecule that is capable of accepting electrons from one molecule and donating it to another in process of electron transport

Question 9

What are the two most common electron carriers in cell respiration? Give oxidized and reduced form

Answer 9

1. NAD+–> NADH + H+
2. FAD+ –> FADH2

FAD and NAD are reduced

Question 10

When does oxidative phosphorylation take place?

Answer 10

During ETC and chemiosmosis

Question 11

Phosphorylation and its effect

Answer 11

Addition of phosphate groups, making molecule less stable and reaction occurs faster

Question 12

Glycolysis: Why are lipids and proteins not preferred compared to carbs?

Answer 12

Lipids are harder to transport and digest but will yield more energy. Proteins can release dangerous nitrogenous compounds

Question 13

Glycolysis: Where does it occur?

Answer 13

In the cytosol

Question 14

Glycolysis: Summary of process

Answer 14

1. Hexose is broken down into molecules of pyruvate (3C) + one phosphate group through hydrolysis
2. Two hydrogen carriers are reduced
3. Net total of 2 ATP molecules are produced

Question 15

Glycolysis: Where does energy go when glucose molecule is broken down?

Answer 15

Most of the potential energy is retained in the two pyruvates

Question 16

Glycolysis: Where is there net total of 2 ATP?

Answer 16

Phosphate group from pyruvate is added back to initial 2 ADP however other inorganic phosphate groups are also present so they get added to ADP due to energy release. 4 ATP produced but 2 were used up in the beginning

Question 17

Glycolysis: What is direct synthesis of ATP called?

Answer 17

Substrate level phosphorylation

Question 18

Glycolysis: What happens to hydrogen in pyruvate molecule?

Answer 18

It reduces NAD+ to NADH. NADH will go through ETC to produce more ATP

Question 19

Glycolysis: How does this process relate to anaerobic respiration?

Answer 19

As glycolysis is the only process that doesn’t require oxygen, only 2 ATP is produced. Pyruvate will be converted to lactic acid or ethanol+CO2

Question 20

Link reaction: What process takes place?

Answer 20

Oxidative decarboxylation

Question 21

Link reaction: Summary of process

Answer 21

• Pyruvate enters matrix
• Enzymes uses O2 to remove one carbon and make CO2 and also remove one hydrogen
• NAD+–> NADH
• CoenzymeA has acetyl group (2C)and becomes acetyl CoA which enters Krebs cycle

Question 22

Link reaction: How many times does reaction occur?

Answer 22

2 pyruvates means link reaction occurs twice per molecule of glucose

Question 23

Link reaction: What does the acetyl group consist of?

Answer 23

2 remaining carbons

Question 24

Krebs cycle: Where does it occur?

Answer 24

Matrix

Question 25

Krebs cycle: Summary of process

Answer 25

- Pyruvate + acetyl CoA enter - 2C + 4C sugar form hexose - Oxidative decarboxylation of 6C=>5C + CO2 - Again 5C=> 4C + CO2 - Between 6-5C and 5-4C, NAD and FAD are reduced and provide electrons for ETC

Question 26

Krebs cycle: What happens to acetyl CoA after decarboxylation?

Answer 26

It becomes CoA which returns to link reaction and is recycled

Question 27

Krebs cycle: How many NADH and FADH2 are produced?

Answer 27

3 NADH and 1 FADH2 per cycle

Question 28

Krebs cycle: How much ATP is produced?

Answer 28

1 ATP per cycle

Question 29

Krebs cycle: How much CO2 is produced?

Answer 29

2 per cycle between each decarboxylation

Question 30

Krebs cycle: How many times does it occur?

Answer 30

Occurs twice as there are two molecules of acetyl CoA

Question 31

How many decarboxylation reactions are there in aerobic respiration?

Answer 31

3. 1 in link reaction and 2 in Krebs cycle

Question 32

What is the max yield of one glucose?

Answer 32

38 ATP

Question 33

ETC: Why does it happen?

Answer 33

Electrons have to be removed as energy to synthesize ATP is derived from oxidation of H carriers

Question 34

ETC: Where does it happen?

Answer 34

Inner mitochondrial membrane

Question 35

ETC: What is the process called?

Answer 35

Oxidative phosphorylation part I

Question 36

ETC: Summary of process

Answer 36

- Oxidization of carriers lead to release of high energy electrons and photons - Energy is used to pump H+ ions in the matrix across inner membrane and electrons lose energy - H+ ions accumulate in inter-membrane space creating conc. gradient - Ions then return to the matrix through ATP synthase down EC gradient

Question 37

Chemiosmosis: What is it?

Answer 37

Diffusion of protons across semi-permeable membrane, through ATP synthase

Question 38

Chemiosmosis: What is the process involved called?

Answer 38

Oxidative phosphorylation part II

Question 39

Chemiosmosis: Summary of process

Answer 39

- Proton motive force will cause H+ ions to move down gradient and diffuse into matrix - Once through ATP synthase, the H+ ions trigger molecular rotation of enzyme, synthesizing ATP

Question 40

Chemiosmosis: Why does reduction of oxygen take place?

Answer 40

- De-energized electrons must be removed for ETC to continue

Question 41

Chemiosmosis: Summary of oxygen reduction

Answer 41

- Oxygen is final electron acceptor for ETC and combination prevents chain from being blocked - O2 also binds with free protons to form water in matrix which removed excess ions and maintains gradient

Question 42

Chemiosmosis: What happens in absence of oxygen?

Answer 42

Hydrogen carriers cannot transfer energized electrons to ETC and ATP production is stopped

Question 43

During aerobic respiration, which sequence do electrons follow?

Answer 43

Glucose>NADH>ETC>Oxygen

Question 44

In cellular respiration, the energy for most ATP synthesis is supplied by?

Answer 44

A proton gradient across a membrane