Respiration Flashcards
Outline Glycolysis
- Glucose phosphorylated (substrate level phosphorylation) with 2 Pi to hexose bisphosphate
(2ATP–>2ADP) - Hexose bisphosphate rearranged by isomerase enzymes to 2 x triose phosphate
- 2 triose phosphate converted to 2 pyruvate by: dehydrogenation & dephosphorylation
(2NAD—>2NADH, 4ADP + 4Pi –> 4ATP)
where does glycolysis occur
cytoplasm of cell
where does link reaction occur
mitochondrial matrix
where does Krebs cycle occur
mitochondrial matrix
where does oxidative phosphorylation occur
inner mitochondrial membrane
outline the link reaction
- pyruvate decarboxylase decarboxylates (removes CO2 from) pyruvate(3C)
& pyruvate dehydrogenase dehydrogenates pyruvate
= forms ACETATE (2C) & (NAD+H) NAD & CO2
- acetate combines with CoA to form Acetyl Coa
state the order of events in respiration
glycolysis, link reaction, Krebs cycle, oxidative phosphorylation
outline Krebs cycle
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)
outline oxidative phosphorylation
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
products of glycolysis per glucose mol
2 ATP, 2 pyruvate, 2 NADH
products of link reaction per glucose mol
2 acetyl CoA, 2 CO2, 2 NADH
products of Krebs cycle per glucose mol
2ATP, 6NADH, 2FADH, 4CO2
3 products of oxidative phosphorylation
ATP, NAD, FAD
how the structure of mitochondria aids respiration
- 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
substrate level phosphorylation and when does it occur during respiration?
formation of ATP by the direct transfer of a phosphate group to ADP from another phosphorylated compound, eg. in glycolysis
why can’t aerobic respiration continue for long time periods?
ethanol and lactate build up is toxic; lactate lowers blood pH
why do we need anaerobic respiration? why wouldn’t respiration continue to produce enough ATP if O2 wasn’t present?
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
anaerobic respiration in fungi such as yeast
ETHANOL FERMENTATION PATHWAY
- Pyruvate decarboxylated to ETHANAL via pyruvate decarboxylase
- ETHANAL accept 2H from 2NADH to form ETHANOL catalysed by ethanol dehydrogenase
anaerobic respiration in mammals such as humans
LACTATE FERMENTATION PATHWAY
- Pyruvate accepts the H (reduced) from NADH to form lactate, catalysed by lactate dehydrogenase
when would anaerobic respiration be appropriate in humans?
when O2 isn’t sufficient to meet short term demand, eg short burst of highly VIGOROUS exercise
what is the fate of lactate?
once O2 becomes sufficient again
Lactate either converted back to pyruvate to enter Krebs cycle OR recycled to glucose & glycogen
why does aerobic respiration have a much higher yield than anaerobic?
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
define:
- respiratory substrate
2. Respiratory quotient
- an organic molecule that can be oxidised by respiration to release energy, used to make ATP
- the efficiency of a substrate: CO2 produced/O2 used
state the different respiratory quotients of the 3 main respiratory substrates
Carbohydrates = 1
Fatty Acids = 0.7
proteins (amino/Keto acids) = 0.9
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?
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
what does an RQ above 1 indicate
some anaerobic respiratory is occurring as more CO2 produced than O2 consumed (decarboxylation occurring but oxidative phosphorylation not occurring)
