Respiration Flashcards
what are the four stages of respiration
- glycolysis
- link reaction
- krebs cycle
- oxidative phosphorylation
what happens in glycolysis
- glucose is phosphorylated by adding 2 phosphates from 2 ATP molecules
- creates 1 molecule of biphosphate and 2 ADP molecules
- hexose biphosphate is split into 2 TP
- TP is oxidised forming 2 molecules of pyruvate
- NAD collects hydrogen ion forming 2 NADH
- 4 ATP produced but 2 are used , net gain of 2 ATP molecules
what are the products of glycolysis
- 2 molecules of NADH go to oxidative phosphorylation
- 2 pyruvate molecules actively transported into the matrix for the link reaction
what happens in the link reaction
- pyruvate is decarboxylated
- NAD is reduced to NADH - collects hydrogen from pyruvate
- pyruvate is changed into acetate
- acetate is combined with coenzyme A to form acetyl coenzyme A
- no ATP produced
how many times does the link reaction need to occur for a glucose molecule
- 2 pyruvate are made for every glucose
- link reaction and Krebs cycle happen twice
- two molecules of acetyl coenzyme A go into the Krebs cycle
- 2 CO2 molecules are released as a waste product
- 2 NADH molecules go into oxidative phosphorylation
what happens in the Krebs cycle
- acetyl group combined with oxaloacetate to form citrate catalysed by citrate synthase
- Coenzyme A goes back to the link reaction
- 6C citrate molecule is converted to 5C
- decarboxylation occurs
- dehydrogenation occurs
- hydrogen used to produce NADH from NAD
- 5C molecule converted to 4C
- decarboxylation and dehydrogenation occur again producing 1 FAD and 2 NADH
- ATP produced through ADP and Pi - substrate level phosphorylation
- citrate converted to oxaloacetate
what are the products of the Krebs cycle
1 Coenzyme A = reused in link reaction
Oxaloacetate = regenerated for Krebs
2 CO2 = released as waste
1 ATP = used for energy
3 NADH = oxidative phosphorylation
1 FADH = oxidative phosphorylation
what happens in oxidative phosphorylation
- energy carried by electrons from reduced coenzymes makes ATP
- takes place in inner mitochondrial membrane
how does oxidative phosphorylation work
- hydrogen released from reduced coenzymes
- electrons move along ETC losing energy at each carrier
- energy used by electrons to pump protons from mitochondrial matrix into intermembrane space
- concentration of protons is higher in intermembrane space than matrix = electrochemical gradient
- protons move down electrochemical gradient into matrix via ATP synthase
- at end of ETC protons, electrons and O2 combine to form water
- oxygen is final electron acceptor
how many ATP molecules can be made from 1glucose molecule
-32
what are the types of anaerobic respiration
- lactate fermentation
- alcoholic fermentation
how does lactate fermentation work
- NADH transfers hydrogen to pyruvate to form lactate and NAD
- NAD used in glycolysis
- production of lactate regenerates NAD
- glycolysis can continue if there isn’t lots of oxygen, small amount of ATP still produced
- cells can tolerate a high lactate level
- too much lactate is toxic and removed from cells into the bloodstream
how does alcoholic fermentation work
- CO2 removed from pyruvate to ethanal
- NADH from glycolysis transfers hydrogen to ethanal to form ethanol and NAD
- NAD reused in glycolysis
what is the respiratory quotient
volume of carbon dioxide produced when the substrate is respired / volume of oxygen consumed in a set period of time
what is the respiratory quotient for some substances
Lipids = 0.7
Proteins / amino acids = 0.9
Carbohydrates = 1
- higher than 1 = anaerobic respiration
