TOPIC 5 - respiration

Question 1

name the 4 main stages of aerobic respiration + where they occur?

Answer 1

• glycolysis - cytoplasm
• link reaction - mitochondrial matrix
• Krebs cycle - mitochondrial matrix
• oxidative phosphorylation - via ETC : membrane of cristae

Question 2

outline stages of glycolysis?

Answer 2

• glucose is phosphorylated to glucose phosphate by 2x ATP
• glucose phosphate splits into 2x triose phosphate (TP)
• 2x TP is oxidised into 2x pyruvate
• net gain of 2x NADH and 2x ATP per glucose

Question 3

how does pyruvate from glycolysis enter the mitochondria?

Answer 3

via active transport

Question 4

what happens during the link reaction?

Answer 4

1. oxidation of pyruvate to acetate
2. pyruvate is decarboxylated = net gain 1x co2
   pyruvate is dehydrogenated = net gain 2x H to reduced NAD to NADH
3. acetate combined with Co enzyme A= acetyl CoA

Question 5

give summary equation for the link reaction.

Answer 5

pyruvate + NAD + CoA –> acetyl CoA + reduced NAD + Co2

Question 6

what is produced in the Krebs cycle?

Answer 6

series of redox reactions produces:
1. ATP by substrate level phosphorylation
2. reduced coenzymes
3. Co2 by decarboxylation

Question 7

outline the stages of Krebs cycle?

Answer 7

1. Acetyl CoA (2c) joins (4C) compound = (6C) citrate
   CoA is released in this reaction
2. (6C) citrate is decarboxylated releasing 2Co2
3. citrate is also dehydrogenated = releasing H atoms needed to reduce FAD and 3NAD
   4.Substrate-linked phosphorylation
   A phosphate is transferred from one of the intermediates to ADP, forming 1 ATP

products per cycle =
- 3 x NADH
- 1 x ATP
- 1 x FADH
- 2 x CO2

Question 8

what is electron transfer chain?

Answer 8

series of carrier proteins embedded in membrane of the cristae of mitochondria
produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration

Question 9

what happens in the electron transfer chain?

Answer 9

electrons released from reduced NAD and FAD
electrons pass along the ETC in a series of redox reactions
energy released is coupled to maintain proton gradient
energy released joins ADP + pi = ATP
oxygen is the final electron accpetor

Question 10

how is a proton gradient established during chemiosmosis in aerobic respiration?

Answer 10

• energy released from ETC is coupled to the active transport of H+ ions from the mitochondrial matrix to the inter-membrane space

Question 11

how does chemiosmosis produce ATP during aerobic respiration?

Answer 11

H+ ions move down their conc gradient from the inter membrane space into the mitochondrial matrix via channel proteins and ATP synthase
ATP synthase catalyses ADP + Pi —> ATP

Question 12

state the role of oxygen in aerobic respiration?

Answer 12

• final electron acceptor in ETC
• produces water as by porduct

Question 13

what is the benefit of ETC rather than a single reaction?

Answer 13

• releases heat gradually
• less energy is released as heat

Question 14

name two types of molecules that can be used as alternative respiratory substrates?

Answer 14

protein - amino acids
lipids - triglycerides

Question 15

how can lipids act as an alternative respiratory substrate?

Answer 15

lipid —-> glycerol + fatty acids
phosphorylation of glycerol –> TP for glycolysis
fatty acid —> acetate for link reaction
H atoms produced for oxidative phosphorylation

Question 16

how can amino acids act as an alternative respiratory substrate?

Answer 16

deamination produces:
- 3C compounds –> pyruvate for link reaction
- 4C/5C compounds —> intermediates in krebs cycle

Question 17

name the stages in respiration that produces ATP by substrate level phsphorylation?

Answer 17

glycolysis ( anaerobic)
krebs cycle (aerobic)

Question 18

what happens during anaerobic respiration in animals?

Answer 18

each pyruvate take up 2 H atoms from NADH to form lactate and NAD

Question 19

what happens to the lactate produced in anaerobic respiration?

Answer 19

transported to liver via bloodstream where it is converted to pyruvate

can enter link reaction or be converted to glycogen

Question 20

what happens during anaerobic respiration in plant and yeast cells?

Answer 20

pyruvate is decarboxylated to form ethanal

ethanal is reduced to ethanol using reduced NAD to produced oxidised NAD for further glycolysis

Question 21

what is the + for producing ethanol/lactate during anaerobic respiration?

Answer 21

converts reduced NAD back into NAD so glycolysis can continue

Question 22

what is the - of producing ethanol during anaerobic respiration?

Answer 22

cells die when ethanol conc is above 12%

ethanol dissolves cell membranes

Question 23

what is the - of produced lactate during anaerobic respiration?

Answer 23

acidic - reduced pH

results in muscle fatigue

Question 24

compare aerobic and anaerobic respiration?

Answer 24

• involve glycolysis
• require NAD
• produce ATP

Question 25

contrast aerobic and anaerobic respiration?

Answer 25

aerobic: - produces ATP by the substrate level phosphorylation and oxidative phosphorylation - produces much more ATP -does not produce lactate or ethanol Anaerobic: -produces ATP by substrate level phosphorylation only -fewer ATP produced -produces lactate and ethanol

Question 26

Suggest have a student could investigate the effect of a named variable on the rate of respiration of a single celled organism?

Answer 26

- use respirometer = pressure changes in boiling tube causes a drop of coloured liquid to move -use a dye as a terminal electron acceptor for the ETC

Question 27

What is the purpose of a sodium hydroxide solution in a respirometer set up to measure the rate of aerobic respiration?

Answer 27

Absorb carbon dioxide so that there is a decrease in pressure as oxygen is consumed

Question 28

How could the student calculate the rate of respiration using a respirometer?

Answer 28

Volume of oxygen produced or carbon dioxide consumed/ time x mass of sample volume = distance moved by coloured drop x ( 0.5 x capillary tube diameter)^2 x pi(3.142)