respiration Flashcards
what is the equation for respiration
glucose + oxygen = carbon dioxide + water + light
where does glycolysis happen
cytoplasm
what are the steps of glycolysis
- phosphorylation of glucose by 2 ATP makes glucose more reactive, converting to glucose phosphate
- glucose phosphate is split into 2 3-carbon molecules known as triose phosphate
- oxidation of each triose phosphate occurs by removal of hydrogen, to form 2 molecules of pyruvate
- NAD accepts hydrogen and is reduced to NADH
- substrate level phosphorylation of 2x triose phosphate to 2x pyruvate produced 4x ATP
what is the net gain from glycolysis
2 ATP and 2 NADH
where does the link reaction happen
in the matrix of the mitochondria
what are the steps of the link reaction
- pyruvate is actively transported from cytoplasm to mitochondrial matrix
- pyruvate is oxidised to acetate
NAD is reduced to NADH / carbon dioxide released - acetate combines with coenzyme A to produce acetyl coenzyme A
how many times does the link reaction happen per glucose
twice
what is a coenzyme
a molecule that helps an enzyme carry out its function but is not used in the reaction itself → consists of a vitamin and a nucleoside
where does the krebs cycle happen
matrix of the mitochondria
what are the steps of the krebs cycle
- acetyl coenzyme A reacts with a 4C compound producing a 6C compound → coenzyme A is released to be reused
- 6C molecule reverted to 4C molecule in a series of redox reactions
hydrogen atoms removed in oxidation reactions reduce 3x NAD to NADH and 1x FAD to FADH
2 molecules of CO2 released
1x ATP produced by substrate level phosphorylation
the 4C compound enters the cycle again
what is the net gain of the krebs cycle
2 ATP, 6 NADH, 2 FADH, 4 CO2
where does oxidative phosphorylation happen
inner membrane of the mitochondria
what are the steps of oxidative phosphorylation
- reduced NAD and FAD release hydrogen, which become proton and electron
2H -> 2H+ + 2e-
- electron is passed along the electron transport chain in a series of redox reactions, releasing energy
→ the energy is used to pump protons into the inter membrane space
- chemiosmosis → protons diffuse back into matrix through ATP synthase
→ energy released by protons combines ADP + Pi to form ATP
- oxygen acts as the terminal electron acceptor, combining with the electron and proton to form water
→ oxygen is essential to make 34 molecules of ATP by oxidative phosphorylation
how many molecules of ATP do NADH and FADH produce respectively and why
3 and 2 because FADH enters later long the electron transport chain
what is the net total of ATP in respiration
38
how are lipids used as an alternative respiratory substrate
lipids → glycerol + fatty acids
triose phosphate enters glycolysis
2 carbon fragments → acetyl coenzyme A (krebs cycle)
hydrogen atoms → oxidative phosphorylation
when are lipids used
provide 2x more ATP than carbohydrates per gram / used in prolonged exercise / fasting when glucose levels are low
how and when are proteins used as an alternative respiratory substrate
- hydrolysed into constituent amino acids
- amino group removed, entering respiratory pathway at different points depending on number of carbon atoms
→ carbon skeleton converted into 3C → pyruvate (glycolysis) → 4/5C → intermediates in krebs cycle
as a last resort
what happens in the anaerobic respiration of animal cells
- pyruvate reduced to lactate via lactate dehydrogenase, using hydrogen from NADH
- NADH oxidised to NAD
- small amounts of energy produced
(continuation leads to build up of lactic acid (toxic) → reduces pH of cells affecting enzyme activity → causes fatigue and cramp → lactate transported to liver in cori cycle)
what happens in the anaerobic respiration of plant cells
- pyruvate reduced to ethanol and CO2 via pyruvate decarboxylase, using hydrogen from NADH
- NADH oxidised to NAD
(ethanol fermentation used in brewery and baking and is irreversible)
what is the respiratory quotient
RQ = volume of CO2 produced / volume O2 used
gives information on respiratory substrate used / type of respiration
