C18 - Respiration

Question 1

What is respiration

Answer 1

Breakdown of complex organic molecules linked to synthesis of ATP

Question 2

What is the first stage of anaerobic respiration?

Answer 2

Glycolysis (cytoplasm) - glucose split into two 3C pyruvate molecules
Anaerobic

Question 3

Explain glycolysis

Answer 3

1) Phosphorylation - 2 molecules of ATP, ATP releases 2 phosphates binding to glycose, form hexose bisphosphate (requires 2x ATP)
2) Lysis - destabilises molecule, splits into 2x triose phosphate
3) Phosphorylation -phosphate added to each triose phosphate, forms 2x triose bisphosphate
4) Dehydrogenation and formation of ATP - 2x triose bisphosphate are oxidised by removal of H atoms, form 2x pyruvate, NAD coenzymes accept removed H forming NADH, 4 ATP produced

Question 4

Why is glycolysis an example of substrate level phosphorylation

Answer 4

ATP formed without electron transport chain

Question 5

What is the net yield of ATP from glycolysis

Answer 5

2

Question 6

Structure of the mitochondria

Answer 6

Question 7

What is the link reaction

Answer 7

Oxidative decarboxylation (link reaction)
EUK - pyruvate enters mitochondrial matrix
1) CO2 removed from pyruvate and H removed from pyruvate (forming NADH), forming 2C acetyl group
2) Acetyl group bound by coenzymeA forming acetylcoenzymeA
3) Acetyl CoA delivers acetyl group to Krebs cycle, NADH used in oxidative phosphorylation
4) CO2 is a final product

Question 8

What is the Krebs cycle

Answer 8

Occur in mitochondrial matrix
1) Acetyl CoA delivers acetyl group to Krebs cycle, 2C acetyl group combines with 4C oxaloacetate to form 6C citrate
2) Citrate undergoes decarboxylation and dehydrogenation producing reduced 1x NAD and CO2, 5C carbon compound formed
3) 5C compound undergoes decarboxylation and dehydrogenation, eventually regenerating oxaloacetate
OVERALL: 2 CO2, 3 reduced NAD, 1 ATP, 1 reduced FADH

Question 9

What is the similarities and differences of coenzymes is respiration

Answer 9

NAD and FAD are coenzymes that accept protons and electrons during the breakdown of glucose in respiration

NAD takes part in all stages, FAD only involved in Krebs cycle
NAD accepts of H, FAD accepts 2 H
Reduced NAD oxidised at start of electron transport chain releasing protons and electrons, FAD oxidised further along
Reduced NAD produces 3 ATP molecules, reduced FAD produced 2 ATP molecules

Question 10

What is oxidative phosphorylation

Answer 10

1) Hydrogen atoms collected by reduced NAD and FAD are delivered to electron transport chain in membranes of cristae of mitochondria
2) H atoms dissociate into H ions and electrons
3) High energy electrons used in synthesis of ATP by chemiosmosis
4) Energy released in redox reactions as electrons reduce and oxidise electron carriers
5) Energy used to create proton gradient leading to diffusion of protons thru ATP synthase resulting in synthesis of ATP
6) At end of ETC, electrons combine with H ions and oxygen to form water, oxygen in final electron acceptor (aerobic)

Question 11

What is substrate level phosphorylatiom

Answer 11

Production of ATP involving transfer of phosphate group from an intermediate

Question 12

How many molecules of ATP does aerobic respiration produce per glucose molecule?

Answer 12

38

Question 13

How many molecules of ATP does fermentation produce per glucose molecule?

Answer 13

2

Question 14

What is fermentation

Answer 14

Process by which complex organic compounds are broken down into simpler inorganic compounds without the use of oxygen or the involvement of an electron transport chain

Question 15

Why does fermentation produced less ATP?

Answer 15

Glucose not fully broken down
Small quantity of ATP only synthesised by substrate level phosphorylation

Question 16

What are the end products of fermentation

Answer 16

Plant root cells and yeast undergo alcoholic fermentation - produced ethanol and CO2
Animal cells lactate fermentation - produced lactate

Question 17

What does the removal of oxygen inhibit in respiration

Answer 17

Cannot act as final electron acceptor in electron transport chain, flow of electron stops
Synthesis of ATP by chemiosmosis stops
Reduced NAD and FAD not oxidised as nowhere for electrons to go
NAD and FAD cannot be regenerated for Krebs cycle so it stops
Glycolysis stops as there is lack of NAD (but instead anaerobic respiration occurs)

Question 18

Describe lactate fermentation in mammals

Answer 18

1) Pyruvate acts ad hydrogen acceptor taking hydrogen from NAD catalysed by lactate dehydrogenase
2) Pyruvate converted to lactate and NAD regenerated
3) Lactic acid converted to glucose in liver but O2 needed, oxygen debt

Question 19

Describe alcoholic fermentation in yeasts/plants

Answer 19

Not reversible

1) Pyruvate converted to ethanal catalysed by pyruvate decarboxylase
2) Ethanal accepts H atom from reduced NAD becoming ethanol
3) Regenerated NAD continues to act as coenzyme allowing glycolysis to continue
4) Ethanol is toxic waste product and are unable to survive at conc above 15%

Question 20

Why can lactate fermentation not occur indefinitely

Answer 20

Reduced quantity of ATP produced is not enough to maintain vital processes over long periods of time

Accumulation of lactic acid causes fall in pH leading to proteins denaturing, respiratory enzymes and muscle filaments denature

Question 21

What is a respiratory substrate

Answer 21

Organic molecules broken down in respiration

Question 22

Describe relative energy of different organic molecules

Answer 22

lipids > alcohol > carbs + protein

Question 23

Describe how triglycerides act as respiratory substrate

Answer 23

-hydrolysed into fatty acids, enter Krebs cycle via CoA and glycerol
-glycerol converted to pyruvate and undergoes oxidative decarboxylation producing acetyl group
-acetyl group bound to CoA forming acetyl CoA
-form as many as 50 acetyl CoA, synthesis of 500 ATP molecules

Question 24

Describe how protein acts as respiratory substrate

Answer 24

-hydrolysed to amino acids
-amino acids are deaminated
-enter pathway via pyruvate
require ATP, reducing net production of ATP

Question 25

What is RQ

Answer 25

Respiratory quotient of a substrate is calculated by dividing the volume of CO2 released by the volume of O2 taken in during respiration of particular substrate Measured using respirometer RQ = CO2 produced / O2 consumed

Question 26

respirometer

Answer 26

Used to investigate effect of XXX on rate of respiration KOH solution absorbs CO2 Changes in volume of air is due to O2 uptake Read different coloured fluid values

Question 27

What is the RQ of

Answer 27

Carbohydrates: 1.0 Protein: 0.9 Lipids: 0.7