Respiration

Question 1

Outline Glycolysis

Answer 1

1. Glucose phosphorylated (substrate level phosphorylation) with 2 Pi to hexose bisphosphate
   (2ATP–>2ADP)
2. Hexose bisphosphate rearranged by isomerase enzymes to 2 x triose phosphate
3. 2 triose phosphate converted to 2 pyruvate by: dehydrogenation & dephosphorylation
   (2NAD—>2NADH, 4ADP + 4Pi –> 4ATP)

Question 2

where does glycolysis occur

Answer 2

cytoplasm of cell

Question 3

where does link reaction occur

Answer 3

mitochondrial matrix

Question 4

where does Krebs cycle occur

Answer 4

mitochondrial matrix

Question 5

where does oxidative phosphorylation occur

Answer 5

inner mitochondrial membrane

Question 6

outline the link reaction

Answer 6

1. pyruvate decarboxylase decarboxylates (removes CO2 from) pyruvate(3C)
   & pyruvate dehydrogenase dehydrogenates pyruvate

= forms ACETATE (2C) & (NAD+H) NAD & CO2

2. acetate combines with CoA to form Acetyl Coa

Question 7

state the order of events in respiration

Answer 7

glycolysis, link reaction, Krebs cycle, oxidative phosphorylation

Question 8

outline Krebs cycle

Answer 8

Acetyl CoA (2c) + Oxaloacetate (4c) –> Citrate & CoA released for reuse

Citrate decarboxylated & dehydrogenated to a 5C compound (NADH and CO2 formed)

the 5c compound is then decarboxylated, 2xdehydrogenated, dephosphorylated, & dehydrogenated again
(FORMS CO2, 2NADH, ATP, FADH)

Question 9

outline oxidative phosphorylation

Answer 9

H atoms released from NADH & FADH split into e- & H+

e- enter ETC; where O2 is final acceptor

H+ protons pumped into inter membrane space using energy released by ETC

H+ diffuses down electrochemical gradient, back into the matrix via ATP synthase (facilitated diffusion)

CHEMIOSMOSIS: the movement of H+ through ATP synthase drives synthesis of ATP from ADP + Pi

H+ combines with the O2 & e- to form H2O

Question 10

products of glycolysis per glucose mol

Answer 10

2 ATP, 2 pyruvate, 2 NADH

Question 11

products of link reaction per glucose mol

Answer 11

2 acetyl CoA, 2 CO2, 2 NADH

Question 12

products of Krebs cycle per glucose mol

Answer 12

2ATP, 6NADH, 2FADH, 4CO2

Question 13

3 products of oxidative phosphorylation

Answer 13

ATP, NAD, FAD

Question 14

how the structure of mitochondria aids respiration

Answer 14

• matrix contains the enzymes needed (dehydrogenases, decarboxylases)
• matrix contains, FAD, NAD, Oxaloacetate
• outer membrane contins transport proteins for pyruvate
• inner membrane is folded (cristae) to maximise surface area for ETC and ATP synthase proteins

FOR LOCALISED PROTEIN SYNTHESIS: (can meet demand for enzymes quicker than if transporting from outside mitochondria)

• DNA in mitochondria codes for these enzymes
• mitochondrial ribosomes (similar to those prokaryotes) for those enzymes to be synthesised

Question 15

substrate level phosphorylation and when does it occur during respiration?

Answer 15

formation of ATP by the direct transfer of a phosphate group to ADP from another phosphorylated compound, eg. in glycolysis

Question 16

why can’t aerobic respiration continue for long time periods?

Answer 16

ethanol and lactate build up is toxic; lactate lowers blood pH

Question 17

why do we need anaerobic respiration? why wouldn’t respiration continue to produce enough ATP if O2 wasn’t present?

Answer 17

if no O2, no final acceptor of ETC so H+ conc. gradient across inner mitochondrial membrane reduces

reduces chemiosmosis so OP ceases

NADH & FADH can’t be deoxidised so Krebs cycle stops, therefore link reaction stops, and glycolysis couldn’t continue

we need something to accept H from NADH FADH to allow glycolysis to continue producing ATP to survive

Question 18

anaerobic respiration in fungi such as yeast

Answer 18

ETHANOL FERMENTATION PATHWAY

1. Pyruvate decarboxylated to ETHANAL via pyruvate decarboxylase
2. ETHANAL accept 2H from 2NADH to form ETHANOL catalysed by ethanol dehydrogenase

Question 19

anaerobic respiration in mammals such as humans

Answer 19

LACTATE FERMENTATION PATHWAY

1. Pyruvate accepts the H (reduced) from NADH to form lactate, catalysed by lactate dehydrogenase

Question 20

when would anaerobic respiration be appropriate in humans?

Answer 20

when O2 isn’t sufficient to meet short term demand, eg short burst of highly VIGOROUS exercise

Question 21

what is the fate of lactate?

Answer 21

once O2 becomes sufficient again

Lactate either converted back to pyruvate to enter Krebs cycle OR recycled to glucose & glycogen

Question 22

why does aerobic respiration have a much higher yield than anaerobic?

Answer 22

in aerobic: Oxidative phosphorylation produces 28 ATP per glucose mol, Krebs produces 2

BUT anaerobic only involves glycolysis so only produces 2ATP per glucose mole

Question 23

define:

1. respiratory substrate

2. Respiratory quotient

Answer 23

1. an organic molecule that can be oxidised by respiration to release energy, used to make ATP
2. the efficiency of a substrate: CO2 produced/O2 used

Question 24

state the different respiratory quotients of the 3 main respiratory substrates

Answer 24

Carbohydrates = 1
Fatty Acids = 0.7
proteins (amino/Keto acids) = 0.9

Question 25

Lipids have the highest energy value per mol, then proteins, then carbohydrates. why is this? and why do we mainly use glucose if this is the case?

Answer 25

lipids have a greater proportion of H, so more ATP produced via chemiosmosis BUT RQ is lower as more O2 is needed to accept these H's so Carbohydrates are more O2 efficient

Question 26

what does an RQ above 1 indicate

Answer 26

some anaerobic respiratory is occurring as more CO2 produced than O2 consumed (decarboxylation occurring but oxidative phosphorylation not occurring)