Respiration (12) Flashcards
What are the 4 stages of aerobic respiration?
1) glycolysis
2) link reaction
3) krebs cycle
4) oxidative phosphorylation
Where does glycolysis occur?
cytoplasm
Where does the link reaction occur?
mitochondrial matrix
Where does the krebs cycle occur?
membrane of cristae
What is not required for glycolysis?
oxygen
What is glycolysis?
breakdown of hexose sugar into pyruvate
What are the 3 stages of glycolysis?
activation
splitting
oxidation
What happens during activation in glycolysis?
glucose is phosphorylated to glucose phosphate by the conversion of 2 ATP into 2 ADP, making the glucose more reactive (activating it)
What happens during splitting in glycolysis?
glucose phosphate (6C) is split into 2 triose phosphate
How many carbons is glucose phosphate?
6
How many carbons is pyruvate?
3
What happens during oxidation in glycolysis?
- 2 pairs of hydrogen atoms are removed and collected by 2 NAD
- 2 phosphate ions are removed from each triose phosphate and combine with 4 ADP, forming 4 ATP
- therefore, 2 triose phosphate are oxidised to 2 pyruvate
Draw the diagram showing glycolysis
Look at notes
Draw the diagram showing the link reaction
Look at notes
What happens to pyruvate formed during glycolysis?
enters the mitochondria via active transport for the link reaction
What is the purpose of the link reaction?
connects glycolysis to krebs cycle
What does the link reaction need?
requires presence of oxygen but does not use it
What are the 3 steps of the link reaction?
1) oxidation of pyruvate to acetate releases carbon dioxide
2) pyruvate dehydrogenase removes 2 hydrogen atoms from pyruvate, forming 1 NADH
3) acetate combines with coenzyme A (CoA) to form acetyl coenzyme A
What is the equation summarising the link reaction?
2 pyruvate + 2NAD + 2CoA > 2CO2 + 2NADH + 2 acetyl coenzyme A
What is the krebs cycle?
oxidation of acetate to carbon dioxide using a series of redox reactions
What does the krebs cycle need?
requires presence of oxygen but does not use it
For each acetate produced, what other 3 substances are produced during the krebs cycle and how?
- 2 carbon dioxide from decarboxylation
- 1 ATP by substrate-level phosphorylation
- coenzymes > 3 NADH and 1 FADH
Why is acetyl CoA able to bind to citrate?
oxaloacetate changes shape of active site so it is now complementary
Draw the diagram showing the krebs cycle.
Look at notes
What are the 8 stages of the krebs cycle?
1) CoA releases acetate which joins to oxaloacetate and makes citrate
2) decarboxylation of citrate produces 1 CO2 and 1 5C compound
3) oxidation of citrate means H atoms are removed by dehydrogenase and accepted by NAD
4) decarboxylation of 5C compound produces 1 CO2 and 1 4C compound
5) oxidation of 5C compound
6) substrate-level phosphorylation means phosphate is taken from glucose and added to ADP to form ATP
7) oxidation of 4C compounds - this time the hydrogen atoms removed by dehydrogenase are accepted by FAD not NAD
8) oxidation of another 4C compound
How many carbons is acetate?
2
How many carbons is oxaloacetate?
4
How many carbons is citrate?
6
What happens in decarboxylation?
carboxyl group is removed
What is the electron transfer chain?
series of carrier proteins embedded in membrane of mitochondrial cristae
What is the purpose of the electron transfer chain?
produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration
How is the electron transfer chain used in chemiosmosis during oxidative phosphorylation?
1) electrons released from NADH and FADH undergo successive redox reactions
2) energy released is coupled to maintaining proton gradient or released as heat
3) oxygen act as final electron acceptor in aerobic respiration, producing water as a byproduct
What does oxidative phosphorylation involve?
electron transport chain
chemiosmosis
What are the 6 steps of oxidative phosphorylation?
1) NADH + FADH becomes NAD + FAD + hydrogen + electron
2) electron passes down electron transfer chain
3) electron energy pumps hydrogen ions from matrix to intermembrane space
4) proton gradient established
5) chemiosmosis uses ATP synthase to produce ATP from ADP and Pi
6) oxygen + electron + hydrogen ion produces water
How is the proton concentration gradient established?
some energy released from electron transfer chain is coupled to the active transport of H+ (protons) from the mitochondrial matrix into the intermembrane space
How does chemiosmosis produce ATP?
H+ move down their concentration gradient from the intermembrane space into the mitochondrial matrix via the channel protein ATP synthase
What are 2 benefits of using an electron transfer chain rather than a single reaction?
- energy is released gradually
- less energy is released as heat
What can be used as alternative respiratory substances?
- amino acids from proteins
- glycerol + fatty acids from lipids
What can aa from proteins and glycerol + fatty acids from lipids be used as?
alternative respiratory substances
How can glycerol be used as an alternative respiratory substance?
phosphorylation of glycerol to triose phosphate for glycolysis
How can fatty acids be used as an alternative respiratory substance?
used as acetate
How can amino acids be used as an alternative respiratory substance?
deamination produces pyruvate for link reaction and the 4C/5C compounds for the krebs cycle
What is the only process used by anaerobic respiration?
glycolysis
What is the process of anaerobic respiration in animals?
NADH + pyruvate produces oxidised NAD + lactate
What happens to lactate once it is produced?
transported to the liver via bloodstream where it is oxidised to pyruvate so it can either enter the link reaction in liver cells or be converted into glycogen
What is the process of anaerobic respiration in yeast and some plant cells?
pyruvate is decarboxylated to form ethanal, which is then reduced to ethanol using NADH to produce oxidised NAD
What can the process of yeast/plant anaerobic respiration be referred too as?
alcoholic fermentation
What can the process of animal anaerobic respiration be referred too as?
lactate fermentation
Draw diagram for anaerobic respiration in yeast/some plant cells?
Look at notes
Why do ethanol and lactate convert NADH back into NAD?
so glycolysis can continue
What are 2 disadvantages of ethanol being produced?
- cells die when ethanol concentration is above 12%
- ethanol dissolves cell membranes
What are 2 disadvantages of lactate being produced?
- acidic so decreases pH
- results in muscle fatigue
What are 3 similarities between aerobic and anaerobic respiration?
- both involve glycolysis
- both require NAD
- both produce ATP
What are 3 differences between aerobic and anaerobic respiration?
- aerobic produces ATP by substrate-level phosphorylation and oxidative phosphorylation, anaerobic only uses substrate-level phosphorylation
- aerobic produces a lot of ATP, anaerobic produces fewer ATP
- aerobic does not produce ethanol or lactate, anaerobic produces ethanol and lactate
What are the 2 steps on how you can investigate the effect of a named variable on the rate of respiration of a single-celled organism?
1) use respirometer (pressure changes in boiling tube cause a drop of coloured liquid to move)
2) use a dye as the terminal electron acceptor for the ETC
Why is sodium hydroxide solution put in a respirometer to measure rate of aerobic respiration?
absorbs CO2 so that there is a net decrease in pressure as oxygen is consumed
How do you calculate the rate of respiration using a respirometer?
volume of oxygen produced or CO2 consumed
___________________ x mass of sample
time
with volume being:
distance moved by coloured drop x (0.5 x capillary tube diameter) x pie
