Respiration

Question 1

What are the 4 stages of aerobic respiration?

Answer 1

1) Glycolysis
2) Link reaction
3) Krebs cycle
4) Oxidative phosphorylation

Question 2

Where does glycolysis occur?

Answer 2

In the cytoplasm

Question 3

What are the 3 steps of glycolysis?

Answer 3

1) Phosphorylation of glucose - glucose phosphate using ATP
2) Production of TP
3) Oxidation of TP into pyruvate with gain of ATP + NADH

Question 4

Describe phosphorylation of glucose

Answer 4

• 2 ATP are hydrolyzed to ADP and each releases a phosphate which attach at each end of the 6C glucose
• Glucose phosphate produced = very high energy

Question 5

Describe production of TP

Answer 5

• Since glucose phosphate is very high energy and highly reactive it will split into 2 3C TP

Question 6

Describe production of pyruvate

Answer 6

• Both TP will be oxidized
• The coenzyme NAD picks up a H from the TP = NAD is now reduced to NADH = TP oxidized
• This forms 2 pyruvate
• 2 ATP produced per pyruvate

Question 7

Why is there a net gain of only 2 ATP when 4 are produced?

Answer 7

• Since we use 2 ATP at the start of glycolysis
• 4 are produced but overall the net gain will be 2 excluding the 2 ATP used

Question 8

What are the products of glycolysis and what happens to them?

Answer 8

• 2 Pyruvate
• 2 NADH
• 2 net gain ATP
  The pyruvate and NADH are actively transported to the mitochondrial matrix

Question 9

Where does the link reaction take place?

Answer 9

In the mitochondrial matrix

Question 10

Describe the link reaction

Answer 10

• Pyruvate is oxidized into a 2C acetate
• The H that is released during oxidation is picked up by coenzyme NAD - NADH
• 1C is released as CO2
• Acetate is then converted into 2C acetylcoenzyme A
• Acetate + Coenzyme A = Acetylcoenzyme A

Question 11

What are the products of the link reaction for a glucose molecule?

Answer 11

• 2 Acetyl CoA
• 2 NADH
• 2 CO2

Question 12

Where does the krebs cycle take place?

Answer 12

In the mitochondrial matrix

Question 13

Describe the krebs cycle

Answer 13

• Acetyl CoA reacts with a 4C releasing CoA back to be recycled = 6C which enters cycle
• Decarboxylation to remove 2C as CO2
• Substrate level phosphorylation will form ATP from ADP + Pi
• A series of redox reactions that reduce 3 NAD and 1 FAD -> NADH + FADH

Question 14

What are the products of the krebs cycle per cycle?

Answer 14

• 3 NADH
• 1 FADH
• 1 ATP
• 2 CO2

Question 15

Where does oxidative phosphorylation take place?

Answer 15

In the mitochondrial cristae

Question 16

Describe oxidative phosphorylation

Answer 16

• NADH + FADH carry the H to the cristae
• The H will split into H+ and e-
• e- move down the ETC through the embedded proteins in the cristae
• As it moves from protein-protein it releases energy
• The H+ is pumped across from matrix to intermembrane space using the energy
• Results in an electrochemical gradient in the IMS
• Go down the concentration gradient via ATP synthase via facilitated diffusion
• Diffusion causes the catalysis and phosphorylation of ADP + Pi = ATP
• Oxygen is the final electron acceptor in the chain
• The O2 in the matrix will pick up e- from the of ETC + H+ that have come back via ATP synthase = H2O
• 1/2(O2) + (2H+)+ 2e- → H2O

Question 17

Why is aerobic respiration only 32% efficient?

Answer 17

• Proton leaks across mitochondrial membrane during oxidative phosphorylation
• ATP used to transport pyruvate and NADH to matrix
• Energy lost as heat

Question 18

What is anaerobic respiration?

Answer 18

-Respiration in the absence of oxygen
- Takes place only in the cytoplasm

Question 19

Describe anaerobic respiration for animals

Answer 19

• Incomplete breakdown of glucose
• Pyruvate is produced at the end of glycolysis and a net gain of 2 ATP
• Pyruvate is reduced by gaining a H+ from NADH which is oxidized to NAD
• Lactate is produced + H2O = Lactic acid which will denature enzymes = muscle fatigue = therefore anaerobic short term
• NAD can be reused in glycolysis and it can keep happening in absence of O2

Question 20

What happens to the lactate produced in anaerobic respiration

Answer 20

• Transported to liver via bloodstream
• Converted into pyruvate
• Can enter the link reaction in liver cells

Question 21

Describe anaerobic respiration for plants and microorganisms

Answer 21

• Incomplete breakdown of glucose
• Pyruvate is produced at the end of glycolysis and a net gain of 2 ATP
• Pyruvate is reduced by gaining a H+ from NADH which is oxidized to NAD
• Ethanol and CO2 is produced
• Ethanol = toxic = denature enzymes = only short term
• NAD can be reused in glycolysis and it can keep happening in absence of O2

Question 22

Compare the efficiency between both respirations

Answer 22

AEROBIC:
- Total yield from 1 glucose molecule is 38 ATP
- More efficient
ANAEROBIC:
- Total yield from 1 glucose molecule is 2 ATP
- Less efficient

Question 23

How do you investigate a variables effect on rate of respiration?

Answer 23

• Use a respirometer
• As the pressure changes in test tube as oxygen is taken in and CO2 is absorbed by NaOH
• Set a timer and see how far the colored liquid moves in a set period of time
• The volume decreases = pressure decreases
• Pressure is higher in the control tube = liquid moves towards experimental tube

Question 24

How do you calculate rate of respiration?

Answer 24

Volume of O2 consumed or CO2 produced/ time * mass of sample
- Volume = π r2 * distance moved by colored liquid

Question 25

Explain the benefit of the respirometer set up

Answer 25

AIR TIGHT: - To prevent air entering and exiting which would change the volume/pressure effecting the movement of colored liquid USE OF NaOH: - Absorbs the CO2 so there is a net decrease in pressure as O2 is consumed and so we can measure the O2 consumed

Question 26

What is the unit for respiration?

Answer 26

Unit volume per time per mass

Question 27

What are some alternative respiratory substrates?

Answer 27

- Proteins: Amino acids - Lipids: Fatty acid + glycerol

Question 28

How can lipids be used as an alternative?

Answer 28

1) Phosphorylation of glycerol = TP for glycolysis 2) Fatty acid = acetate for link reaction 3) H atoms produced for oxidative phosphorylation

Question 29

How can proteins be used as an alternative?

Answer 29

De-amination produces: 1) 3C compounds = pyruvate for link reaction 2) 4/5C compounds = used in Krebs cycle