C1.2 Respiration HL

Question 1

what is the order of processes during respiration?

Answer 1

glycolysis → link reaction → Kreb’s cycle → electron transport chain

Question 2

which parts of respiration need mitochondria (+oxygen)

Answer 2

link reaction + Kreb’s cycle + electron transport chain

Question 3

what types of living organisms have mitochondria?

Answer 3

eukaryotes

Question 4

where does glycolysis take place?

Answer 4

cytoplasm

Question 5

describe the process of glycolysis

Answer 5

This is the first step of breaking down one molecule of glucose in respiration. This takes place inside the cytoplasm.

Glucose will first be phosphorylated by 2 ATP molecules and then split into two 3 carbon molecules called G3P. The two G3P molecules will then be oxidised by 2 NAD+ molecules to remove the phosphates and become known as pyruvate. During this oxidation process, 2 NADH and H+ molecules and 4 ATP molecules will be formed.

Therefore, during glycolysis, one glucose molecule will give a net yield of 2 NADH and H+, 2 ATP molecules and 2 pyruvate molecules.

NAD+ is a hydrogen and an electron carrier and these are needed for the last stage of aerobic respiration.

Question 6

what is phosphorylation

Answer 6

adding a phosphate

Question 7

why is glucose phosphorylated?

Answer 7

makes it unstable and easier to split

• when adding phosphate to something = make unstable
• trying to extract energy to make more ATP

Question 8

what is the net yield of glycolysis?

Answer 8

2 ATP

Question 9

if there is no oxygen, what does pyruvate become in humans?

Answer 9

lactic acid/lactate

Question 10

if there is no oxygen, what does pyruvate become in yeast?

Answer 10

ethanol + CO2

Question 11

describe how pyruvate becomes lactate in humans

Answer 11

pyruvate ←→lactate

H+ + NADH ←→NAD+

H+ + NADH = reduced NAD

Question 12

(when pyruvate becomes lactate) why does NAD+ need to be regenerated?

Answer 12

Needed to regenerate NAD+, so glycolysis can keep going without oxygen (anaerobic respiration can continue)

Question 13

why is it important that the electron carrier returns the electrons?

Answer 13

• without oxygen won’t move into mitochondria
• useless to keep them

Question 14

what is the problem of converting all NAD to reduced NADH?

Answer 14

• if deplete all NAD+, but not using it
• it stops the process at G3P → can’t get 4ATP → losing (2) ATP

Question 15

describe the process of pyruvate becoming ethanol

Answer 15

intermediate = ethanal

• already get CO2 here
• converted into ethanol using reduced NAD → gave away electrons and hydrogen to ethanal and turned it into ethanol

reduced NAD giving the hydrogens and electrons to ethanal to form ethanol

Question 16

give a brief overview of the process of link reaction

Answer 16

1 glucose → 2 x pyruvate → 2 x acetyl CoA

Question 17

where does link reaction occur?

Answer 17

in the matrix of mitochondria

Question 18

what is coenzyme in link reaction?

Answer 18

• coenzyme: a carrier
  
  • non-protein that binds to enzyme to help catalyse reactions
    
    • there are only space for 2 carbons, one carbon from pyruvate needs to be removed, carbon turned into carbon dioxide, need oxygen bc one carbon needs to turn into CO2 by binding with oxygen

Question 19

describe the process of link reaction

Answer 19

Link reaction is the second stage of aerobic respiration. It takes place in the matrix of the mitochondria and requires oxygen.

Coenzyme A(a non-protein that binds to enzymes to help catalysing reactions)and oxygen will split the two molecules of pyruvate in a chemical reaction calledoxidative decarboxylation.

One 3-carbon containing pyruvate will react with oxygen and form one molecule of carbon dioxide, one molecule of Acetyl CoA and 1 NADH and H+. And since there are 2 pyruvate molecules from glycolysis, the net yield will be 2 carbon dioxide, 2 Acetyl CoA and 2 NADH and H+.

No ATP is formed here.

Question 20

explain cell respiration using fatty acids

Answer 20

CH3(CH2)nCOOH

• fatty acids have a long chain of carbon atoms
• glycolysis is not needed → comes in directly in link reaction
• CoA can oxidise this chain - break it down
• it makes Acetyl CoA with two carbons + break it off
• and carries them to the krebs cycle

Question 21

is glycolysis needed in cell respiration using fatty acids?

Answer 21

no, comes in directly in link reaction

Question 22

how long can cell respiration using fatty acids last?

Answer 22

can make it until all the carbon is used up

Question 23

what happens if there is an odd number of carbon during cell respiration using fatty acids?

Answer 23

if there is an odd number → the remaining carbon atom is released as carbon dioxide

Question 24

how many acetyl CoA molecules can be made from:

1 a fatty acid with 24 carbons

2 a fatty acid with 25 carbons

3 a fatty acid with 26 carbons

4 from stearic acid (C18H36O2)

5 this fatty acid: CH3(CH2)54COOH

Answer 24

1: 12
2: 12 + CO2
3: 13
4: 9
5: 28

Question 25

Outline the differences between lipids and carbohydrates as respiratory substrates

Answer 25

• both oxidised in respiration to release energy
• anaerobic respiration possible in carbohydrates but NOT in lipids (bc lipids can’t go through glycolysis)
• krebs cycle (both have??)
  - these stages only happen when oxygen is available → anaerobic respiration not possible with lipids

Question 26

is anaerobic respiration possible for carbohydrates and lipids?

Answer 26

• is anaerobic respiration possible?
  
  • carbohydrates: yes, glycolysis
    
    • 1st stage is glycolysis: generates some ATP, does not require oxygen
    • anaerobic respiration is therefore possible
    • pyruvate can be converted to acetyl groups by the link reaction and the acetyl groups can then be fed into the Krebs cycle → can only happen if oxygen is available
  • lipids: no
    
    • 1st stage: breakdown of fatty acids to acetyl groups in matrix of mitochondrion
    • acetyl groups are then fed into the

Question 27

describe the process of Kreb’s cycle

Answer 27

Kreb’s cycle (also known as citric acid cycle) is the third stage of aerobic respiration. It also takes place in the matrix of the mitochondria and requires oxygen.
Also bear in mind that 2 Acetyl CoA molecules will enter the Kreb’s cycle, so the cycle willrun twice!
1. Oxaloacetate (a 4 carbon molecule) will take the two carbon from one Acetyl CoA molecule to form citric acid (a 6 carbon molecule).
2. Citric acid/citrate will break down into a 5 carbon molecule inoxidative decarboxylation(1 carbon dioxide molecule will be released; 1 NAD+ will be reduced to become NADH and H+).
3. Then the 5 carbon molecule will break down into 4 carbon molecule in oxidative decarboxylation(1 carbon dioxide molecule will be released; 1 NAD+ will be reduced to become NADH and H+).
4. This 4 carbon molecule will rearrange itself to become the oxaloacetate mentioned in step 1 through a process calledsubstrate-level phosphorylation(1 ADP will be converted to ATP; one FAD will be reduced to FADH2; one NAD+ will be reduced to NADH and H+).
And remember, there were 2 Acetyl CoA to start with, hence the Kreb’s cycle will run twice and give you a net yield of:
2 ATP, 6NADH and H+, 2 FADH2 per glucose molecule.

Question 28

why is Kreb’s cycle considered a cycle?

Answer 28

after go back to oxaloacetate it will go through the whole process again

Question 29

what are the 2 types of electron carrier in respiration?

Answer 29

2 types of electron carrier: NADH + H+ (reduced NAD) & FADH2 (reduced FAD)

Question 30

Describe the process of electron transport chain and oxidative phosphorylation

Answer 30

• Electron transport chain is made of a number of integral proteins in the inner mitochondrial membrane
• Final stage of aerobic respiration occurs here
• All the NADH and the FADH2 molecules that were produced inglycolysis,link reactionand theKreb’s cyclewill be used here to release their hydrogen ions (H+) and electrons
• NADH and FADH2 will donate their electrons and hydrogen to the electron transport chain
• Hydrogen ions will pass through some ion channels on the inner mitochondrial membrane and move from the matrix to the inter-membrane space of the cristae
• After donating the electrons, the NADH and FADH2 will become NAD+ and FAD molecules again. They can now be used again in the earlier stages (link reaction or Kreb’s cycle)
• This will create a higher concentration of hydrogen ions in the inter-membrane space than the matrix, hence creating an electrochemical gradient. The hydrogen ions (also known as protons) cannot simply pass through the inner mitochondrial membrane even though there is an electrochemical gradient. The hydrogen ions can only pass through via ATP synthase, which is also an integral protein in the inner mitochondrial membrane. Diffusion of ions through a semi-permeable membrane and down an electrochemical gradient is known aschemiosmosis
• As the hydrogen ions pass through, ATP synthase will rotate and be able to phosphorylate ADP to ATP. As a result, 32 ATP molecules will be made. This process is known asoxidative phosphorylation. Sometimes, 34 ATP molecules will be made, this depends on how electrons were donated to the electron transport chain
• And to conclude the process, the excess hydrogen ions and the electrons from the electron transport chain will react with oxygen in order to form water as a byproduct. Hence oxygen is theterminal electron acceptor. If the excess electrons are not removed by oxygen, then the electric transport chain will stop receiving electrons from NADH, and hence NAD+ inside the mitochondrion will not be recycled, and the link reaction and Kreb’s cycle will stop. So oxygen is very important!!

Question 31

GLYCOLYSIS

1. where does it occur?
2. what is its purpose
3. what is the ATP yield?

Answer 31

1. cytoplasm
2. covert glucose (6C) to pyruvate (2x3C)
3. 2

Question 32

LINK REACTION

1. where does it occur?
2. what is its purpose
3. what is the ATP yield?

Answer 32

1. matrix of mitochondria
2. convert pyruvate to acetyl CoA
3. 0

Question 33

KREBS CYCLE (citric acid cycle)

1. where does it occur?
2. what is its purpose
3. what is the ATP yield?

Answer 33

1. matrix of mitochondria
2. release H+ to electron carriers (NADH and FADH2) for the electron transport chain
3. 2

Question 34

ELECTRON TRANSPORT CHAIN

1. where does it occur?
2. what is its purpose
3. what is the ATP yield?

Answer 34

1. Inner mitochondrial membrane
2. energy to pump H+ to intermembrane space to generate concentration gradient
3. 0

Question 35

OXIDATIVE PHOSPHORYLATION

1. where does it occur?
2. what is its purpose
3. what is the ATP yield?

Answer 35

1. Inner mitochondrial membrane
2. Uses flow of H+ ions through ATP Synthase to phosphorylation ADP to ATP
3. 32

Question 36

what is the total yield of ATP from aerobic respiration?

Answer 36

36 ATP

Question 37

what are the electron carriers in photosynthesis?

Answer 37

NAD+

FAD