Respiration Flashcards
where does link reaction occur in?
mitochondrial matrix
what is the process of link reaction?
- pyruvate enters the mitochondrial matrix by active process via transport protein
- pyruvate will undergo oxidative decarboxylation & oxidative dehydrogenation to form acetyl coenzyme A (acetyl coA).
- it will combine with 2C intermediate compound
- 2 Pyruvate + 2NAD+ -> 2 Acetyl CoA + 2CO2 + 2NADH
what is the process of Krebs cycle?
- acetyl coA (2C) combine with oxaloacetate (4C) to form citrate (6C)
- citrate will undergo dehydrogenation and decarboxylation to form alpha-keto glutamate (5C)
- each decarboxylation step will produce 1CO2
- regeneration of oxaloacetate involves 3 dehydrogenation steps and 1 decarboxylation step
- overall eqn (1 glucose): 2ADP + 6NAD+ 2FADH -> 6NADH + 2ATP + 2FADH2 + 4CO2
where does oxidative phosphorylation occur at?
mitochondrion membrane
what is the process of oxidative phosphorylation?
- In the presence of O2, NADH & FADH2 transfer their high energy electrons to electron carriers of ETC & get oxidized in the process.
- as electrons are passed down electron carriers of increasing electronegativity, energy released is coupled to H+ pumped from matrix to intermembrane space, generating a proton gradient
- H+ protons diffuses through ATP synthase back into matrix, down the gradient by facilitated diffusion.
- ADP is phosphorylated to form ATP via chemiosmosis
- oxidation of NADH & FADH2 allows the regeneration of NAD+ and FAD, allowing them to pick up more electrons from KC, LR & glycolysis -> for these reactions to continue
- O2 act as final e- acceptor at the end of ETC, combining w/ e- and h+ to form H2O
- equation for 1 glucose: 10NADH x 2.5 + 2FADH2 x 1.5 = 28ATP
comparison points of anaerobic respiration in human and yeast [5] (RLPPF)
[similarity]
reason for anaerobic + aerobic:
1. high DD for ATP due higher muscle contractions -> rapid increase in glycolysis -> rapidly deplete (limited) NAD+ -> oxidative phosphorylation is unable to regenerate NAD+ fast enough
2. aim: produce small amount of energy (2ATP) to at least cope w/ cellular processes & to regenerate NAD+ from NADH for glycolysis to continue
[differences]
location:
1. human: muscle cell cytosol
2. yeast: yeast cell cytosol
process:
1. human: pyruvate is reduced by e- from NADH, catalyzed by lactate dehydrogenase to lactate
(2 pyruvate -> 2 lactate + 2ATP)
2. yeast: pyruvate is converted to ethanol & CO2, which is catalyzed by pyruvate decarboxylase -> reduced by e- from NADH to ethanol catalyzed by alcohol dehydrogenase
(2 pyruvate -> ethanal + 2CO2 -> 2 ethanol + 2ATP)
impacts & fate of products:
1. human: lactic acid accumulates in the muscle cell faster than it is being removed -> cause muscle fatigue
lactate will be transported from muscle cells to liver by bloodstream -> convert back to private -> to enter link reaction + krebs cycle -> generate more atp
2. yeast: wine & beer fermentation
final e- acceptor:
1. human: pyruvate
2. yeast: ethanol
what is the process of glycolysis?
P- phosphorylation of glucose
- 2 ATP is invested to undergo phosphorylation and make glucose more reactive and committed to glycolysis
- 2ATP + C6H12O6 -> 2ADP + fructose 1,6-biphosphate
L- lysis
1. phosphorylated glucose lyses to form 2 glyceraldehyde-3-phosphate (G3P)
2. fructose 1,6-biphosphate -> 2G3P
O- oxidation by dehydrogenation
1. 1 G3P will oxidise by dehydrogenation and phosphorylation
2. G3P + Pi + NAD+ -> 1,3 biphosphoglycerate + NADH
S- substrate level phosphorylation
1. dephosphorylate to form ATP & glycerate phosphate
2. glycerate phosphate form pyruvate
3. 1,3 biphosphoglycerate + ADP -> GP+ATP; GP +ADP -> pyruvate + ATP
OVERALL: 1 glucose + 2ATP + 2ADP + 2NAD+ -> 2 pyruvate + 2ATP + 2NADH
Location of Glycolysis?
Location of Link Rxn
Location of Kreb’s Cycle?
Glycolysis: Cytosol
Link Rxn & Kreb’s Cycle: Mitochondrion Matrix (singular)
Describe the Kreb Cycle and its components [4]
Acetyl CoA (2C) formed through link reaction combines with oxaloacetate (4C) to form citrate (6C)
- Citrate is decarboxylated and dehydrogenated to form α-ketoglutarate (5C) & NADH
- Each decarboxylation step results in a loss of carbon as a CO2 molecule
- Regeneration of oxaloacetate (4C) involves 1 decarboxylation step and 3 dehydrogenation steps to
yield 2 NADH, 1 FADH2 1 CO2
What is the final electron acceptor in Ox Phos?
Oxygen
Where does Ox Phos happen?
Mitochondrion membrane
How does Ox Phos generate the proton gradient/p.m.f?
In presence of O2, NADH and FADH2 transfer their high energy electrons to electron carriers of electron
transport chain & get oxidised in the process
- As e- are passed down electron carriers of increasing electronegativity, energy released is coupled to pumping of H+ from matrix into intermembrane space* to generate a proton gradient
Describe the process of Ox Phos [5]
In presence of O2, NADH and FADH2 transfer their high energy electrons to electron carriers of electron
transport chain & get oxidised in the process
- As e- are passed down electron carriers of increasing electronegativity, energy released is coupled to pumping of H+ from matrix into intermembrane space* to generate a proton gradient
- As H+ diffuses through ATP synthase back into matrix* down the gradient by facilitated diffusion,
ADP phosphorylated to form ATP via chemiosmosis - *Oxidation of NADH and FADH2 allows regeneration of NAD+ and FAD, allowing them to pick up more
electrons from Krebs cycle, link reaction & glycolysis, so that these reactions can continue - O2 act as final e- acceptor at end of ETC, combining with e- and H+ to form H2O
When does anaerobic respiration happens?
Exceptionally high DD(ATP) due to higher muscle contractions → rapid increase in glycolysis →
rapidly depletes limited NAD+ as Oxidative Phosphorylation unable to regenerate NAD+ fast
enough
What’s the aim of anaerobic respiration?
Aim: to produce small amount of energy (2ATP) to at least cope with cellular processes & to
regenerate NAD+ from NADH for glycolysis to continue (by having respective final e- acceptor)
After running a 200m race, a man complains of painful thighs and soreness. Explain why [4]
Exceptionally high DD(ATP) due to higher muscle contractions → rapid increase in glycolysis →
rapidly depletes limited NAD+ as Oxidative Phosphorylation unable to regenerate NAD+ fast
enough
Hence, anaerobic respiration took place, to produce small amount of energy (2ATP) to at least cope with cellular processes & to
regenerate NAD+ from NADH for glycolysis to continue
Since Oxygen is absent/low, pyruvate acts as the final e- acceptor
resulting in lactic Acid production and accumulation in muscle faster than it is removed → muscle fatigue
What enzyme is involved in anaerobic respiration in humans and yeast respectively?
Lactate Dehydrogenase
Pyruvate Decarboxylase
Why does the lack of oxygen significantly reduce the ATP yield?
Anaerobic respiration took place in the absence of oxygen, Oxygen serves as the final electron
acceptor* in ETC. Without oxygen, Oxidative Phosphorylation, Link rxn & Krebs cycle stops, thus the bulk of the ATP is not produced
How does ATP get produced in the absence of oxygen?
As NAD cannot be regenerated from NADH in MC → Anaerobic respri takes place in the cytosol via
glycolysis & fermentation with a net of 2 ATP molecules produced glucose molecule via substrate-level phosphorylation during glycolysis
What is the function of NADH & FADH? [4]
When organic molecules get oxidised during glycolysis, link rxn & Krebs cycle, e- released by [o] are
transferred to coenzymes NAD & FAD to form NADH & FADH2 respectively
- They act as mobile e- carriers to carry high energy e- from the organic molecules to ETC on cristae
of mitochondria - High energy e- in NADH & FADH2 act as reducing power to reduce electron carriers on ETC, while
NADH & FADH2 gets oxidised in the process, regenerating NAD & FAD - Allowing them to pick up more e- from glycolysis, link rxn & Krebs cycle, so that these rxn can continue
For essay can elaborate on chemiosmosis, ETC e- flow, how many ATP yield per NAD/FAD
Function of Oxygen [4]
Oxygen is the final electron acceptor at the end of electron transport chain*,
- where it combines with electrons and protons to form water (2e- + 2H+ ½O2 → H2O)
- By removing electrons, oxygen re-oxidises electron transport chain so that NADH* and FADH2 can continue to donate electrons to the chain, thereby allowing oxidative phosphorylation to continue to
produce ATP - NAD & FAD are regenerated, allowing them to pick up more electrons from glycolysis, link rxn & Krebs cycle, so that these rxns can continue
Name the adaptions that mitochondria have to carry out its role well [5]
start with memorising the big header then details
- Compartmentalisation: double membrane of MC isolates Krebs Cycle & Oxidative Phosphorylation from rxns occurring in cytoplasm like glycolysis
–> Improves efficiency/rate as enzymes needed can be concentrated in
compartments & provide optimal conditions for each rxn. E.g Krebs cycle in matrix
- Inner membrane of MC highly folded into cristae → increasing surface area
–> embedding more Electron Carriers involved in ETC & ATP Synthase
- As phospholipid bilayer impermeable to charged ions e.g H+ no diffuse across
–> H+ ions can then accumulate in Intermembrane space as proton pumps pump H+ via active transport → creating a proton gradient across the inner membrane → allowing chemiosmosis
- selective permeability of membrane: allows O2 & Pyruvate from cytosol to diffuse across,
while CO2 can leave as by-product
–> As H+ diffuse across ATP synthase down proton gradient, ADP
phosphorylated to ATP via chemiosmosis → generating large amt of ATP via O.P
- Membrane allows for the localisation of proteins with related functions involved in O.P
→ facilitate sequential & ordered sequence of reactions → improves efficienc
factors affecting respiration?
- O2
- Temperature
- pH of cells
- substrates: glucose
recall they are all ENZYME based answers
How many
(i) NADH
(ii) FADH2
(iii) ATP
is yield from 1 kreb cycle?
1 FADH2
2 ATP
3 NADH
1,2,3
How many ATP is formed from 1 glucose?
34/28 ATP
Does link rxn produce CO2 and ATP?
CO2 evolved BUT NO FORMATION OF ATP
