A2 respiration (topic 5)

Question 1

cellular respiration (how is atp made)

Answer 1

ATP made from the hydrolysis of glucose

Question 2

how many ATP molecules are made in aerobic respiration

Answer 2

38

Question 3

3 ways oxidation can occur

Answer 3

adding O2
removing H2
losing e-

Question 4

step 1 - glycolysis (site and steps)

Answer 4

in cytoplasm (both pro and eukaryotic)

=> phosphorylated glucose: add 2 Pi from 2 ATPs to make it more reactive P - 000000 - P
=> then split: into 2x 3-carbon molecules called triose phosphate P - 000 and 000 - P
=> oxidation: H removed from each triose phosphate molecule and transferred to a hydrogen carrier (NAD)
==> 2 reduced NAD
=> enzyme controlled reactions convert each TP into another 3-carbon molecule (pyruvate)

2 molecules of ATP are regenerated from ADP from each triose phosphate molecule

Question 5

step 2 - link reaction (site and steps)

Answer 5

occurs in matrix of mitochondria to oxidise pyruvate

=> active transport: pyruvate from cytoplasm to matrix
=> 2 reduced NAD / each 3C pyruvate loses H2 (<= accepted by NAD+ to form NADH and H+)
=> 1 CO2 made (decarboxylation)
=> the now 2C acetate combines with coenzymeA to produce acetylcoenzyme A

pyruvate + NAD + CoA => acetylCoA + reduced NAD + CO2

Question 6

step 3 - krebs cycle 

Answer 6

occurs in mitochondria matrix

=> CoA drops off and (2C) acetate combines with (4C) molecule to produce a (6C) molecule citrate
=> 4 CO2 produced as carbons drop off per glucose (2 per cycle)
=> 6 NAD reduced per glucose (3 per cycle)
=> 2 FAD reduced per glucose (1 per cycle)
=> 4C molecule ready to accept another acetate

=> 2 ATP per glucose (1 per cycle)

Question 7

why is krebs important

Answer 7

breaks down macromolecules into smaller ones (pyruvate => CO2)
produces H atoms carried by NAD to the electron transfer chain, provides energy for oxidative phosphorylation

Question 8

oxidative phosphorylation ATP maths

Answer 8

we have 2 reduced FAD => can make 4 ATP (2 per molecule)

we have 10 reduced NAD => can make 30 ATP (3 per molecule)

= 34
+ 4 we made already in glycolysis and krebs
= 38 ATP

Question 9

step 4 - oxidative phosphorylation

Answer 9

reduced NAD (NADH) arrives at cristae inner membrane.
=> loses H and splits it into a p+ and e-
=> e- binds to electron carrier and reduces it
=> e- moves along the electron carriers due to their affinity to e- (reducing next carrier, oxidising previous)
=> this produces energy which allows p+ to move into intermembranal space via active transport (against conc g)
=> final e- acceptor is oxygen. e - combines with a proton to form H, and then with oxygen => water
=> the p+ pumping creates proton gradient. they move along gradient through ATP synthase. this provides energy for ATP synthase to produce ATP

Question 10

anaerobic respiration equation

Answer 10

glucose -> ethanol + co2 + energy

Question 11

steps of anaerobic respiration

Answer 11

glycolysis
fermentation => each pyruvate loses a carbon (2 co2 made)
- forms acetylaldehyde which is reduced and gains 2 hydrogens to form ethanol
- NAD goes in a loop, gets reduced then oxidised so it can be used again in glycolysis as this is the only place ATP is made

in animals: pyruvate doesn’t lose a carbon, only oxidation of NAD by reduction of pyruvate forming lactate