Respiration Flashcards
Aerobic respiration
- breakdown of organic compounds like carbohydrate, in a series of enzyme catalysed reactions using oxygen to produce ATP. ATP breakdown releases energy
Anaerobic respiration
- breakdown of organic compounds like carbohydrate, in a series of enzyme catalysed reactions without oxygen to produced ATP
First step of glycolysis
- activation of glucose by phosphorylation to form glucose phosphate. This requires 2 ATP to be used
Second step of glycolysis
- splitting of glucose phosphate into 2 molecules of triose phosphate (an extra phosphate group is added to each molecule)
Third step of glycolysis
- oxidation of triose phosphate, NAD reduced
Forth step of glycolysis
- each glycerate 3 phosphate (G3P) gives away 2 phosphates forming pyruvate. 4 ATP formed (net gain of ATP)
What is the net gain of glycolysis?
- 2 ATP, 2 pyruvate, 2 NADH
Substrate level phosphorylation
- when a phosphate group is transferred from a substrate molecule to ADP in order to produce ATP
- does not use ATP synthase
Link reaction/oxidative decarboxylation
- pyruvate oxidised to acetate, producing reduced NAD and releasing carbon dioxide
- acetate combines with coenzyme A to produce acetyl coenzyme A
Net gain of link reaction/ oxidative decarboxylation
- 1 NADH, 1 CO2, 1 acetyl-coenzyme A (doubled)
Krebs cycle/ citric acid cycle
- acetylcoenzyme A reacts with a four-carbon molecule, releasing coenzyme A and producing a six-carbon molecule that enters the Krebs cycle
- in a series of oxidation-reduction reactions, the Krebs cycle generates reduced coenzymes and ATP by substrate-level phosphorylation, and carbon dioxide is lost
Products of krebs/citric acid cycle per cycle
- 3 NADH, 1 reduced FAD, 1 ATP, 2 CO2 (doubled if per glucose molecule)
First step of oxidative phosphorylation
- If oxygen present, NADH and FADH2 move from cytoplasm into the matrix, where there are oxidised releasing protons and high energy electrons.
Electrons are passed to electron transport chain (ETC).
Second step of oxidative phosphorylation
- Passage of electrons from one carrier to the next releases energy - this is used to actively pump H+ ions into the intermembrane space from the matrix (against their electrochemical gradient); the energy gradient that exists allows for its gradual release, so less is loss as heat.
Third step of oxidative phosphorylation
- The electrons, along with protons, are used to reduce oxygen to water. Oxygen is therefore final electron acceptor of the ‘ETC’ of oxidative phosphorylation.
Forth step of oxidative phosphorylation
- Hydrogen (by facilitated diffusion) moves back into matrix along a concentration gradient, releasing energy (chemiosmosis) …this allows ATP synthase change its tertiary structure, to phosphorylate ADP to make ATP – approx. 28 made in total
Anaerobic respiration
- ethanol and carbon dioxide (in yeast and some bacteria) (and NAD)
- lactate (in humans and some bacteria) (and NAD)
Explain anaerobic respiration
- Oxygen is the terminal electron acceptor. If there is no oxygen, the ETC comes to a halt, and NADH accumulates. NAD is needed in glycolysis, so the whole process stops
- pyruvate accepts hydrogen from the NADH to become reduced and the NAD is renewed
- pyruvate + NADH -> ethanol +CO2 + NAD
- pyruvate + NADH -> lactate + NAD
When might plants and fungi encounter anaerobic conditions?
- when plant roots in waterlogged soils, when fungi living deep inside rotting fruit, in biotechnology processes that use ethanol fermentation
What does anaerobic respiration cause in animals?
- buildup of lactate leading to muscle fatigue as it causes drop in pH, inhibiting enzymes
Respiring protein
- protein hydrolysed into amino acids
- remove amino groups (deamination)
- products enter respiratory pathway based on number of carbon atoms
Respiratory pathways based on carbon atoms
- 3C compounds converted to pyruvate
- 4C and 5C compounds enter at various places in krebs
Respiring lipid
- hydrolyse triglycerides into glycerol and fatty acids
- phosphorylase the glycerol to triose phosphate - this enters glycolysis/krebs
- break down fatty acids into acetate, which in turn get converted to acetyl coenzyme A - this can now enter krebs
- lipids have higher ratio of C-H bonds to C atoms than carbohydrates, potentially forming more reduced NAD/FAD per molecule
- lipids yield two times more energy than carbohydrates when aerobically respired
What substances move into a mitochondrion?
- pyruvate (Actively pumped into matrix for link reaction), oxygen (inhaled and circulating in the blood then enters cells and diffuse into mitochondria), reduced NAD (from glycolysis), ADP and Pi (for synthesis of ATP via transport protein)
What substances move out of the mitochondrion?
- carbon dioxide (diffuses back into the blood and exhaled), NAD (from electron transport chain for glycolysis), ATP (to be used in cell processes)
Compare and contrast structure of chloroplast and mitochondrion
Similarities: double membrane, circular DNA, ribosomes
Differences: thylakoids vs cristae, stroma vs matrix, chlorophyll vs no chlorophyll, starch grains vs no starch grains
What is respirometer used for?
- tool used to measure how fast an organism breathes or its respiration rate
What does a respirometer measure?
- the volume of oxygen an organism takes in over a set period of time
How does respirometer work?
- absorbs carbon dioxide produced so change in gas volume is due to organism removing oxygen through respiration
What happens if rate of respiration is higher?
- the more the coloured liquid in the respirometer will move
Steps of respirometer respiration
- organism respires using up oxygen
- sodium hydroxide absorbs carbon dioxide produced
- as volume of gas inside the tube changes, oil droplet moves towards the organism as the volume of gas inside the test tube decreased and so did the pressure
What units is respiration measured in?
- mm^3 g-1 hour-1
How can syringe be used to check for leaks in complex respirometer?
- syringe is pressed down changing the level of coloured oil. If there are leaks present, the oil will gradually return to the original level
How is the syringe used to rest the oil droplet to allow readings over a longer time period?
- if 3 way tap, open tap and then use syringe to reset the level of fluid in a manometer
Why does respiration of yeast cause methylene blue to go colourless?
- able to accept electrons and hydrogen ions and when it does, it becomes reduced and goes from blue to colourless as respiration of yeast produces lots of reduced coenzymes due to the activity of many dehydrogenase enzymes
Why is NAD needed in glycolysis?
- NAD reduced to NADH, when each triose phosphate molecule donates a hydrogen and in itself is oxidised
- Without NADH, glycolysis would no longer continue
What is activation energy?
- minimum energy needed for successful collisions where atoms within the reactants rearrange to form products
In what circumstances would the ability for ATP to inhibit enzymes involved in production of glucose phosphate be advantageous?
- When there is limited supply of glucose and cell would not benefit from depleting it all in respiration or when there is already sufficient cellular levels of ATP
Why is it important form plants to product ATP during respiration in addition to photosynthesis?
- in the dark there is no ATP production in photosynthesis, some tissues unable to photosynthesise, ATP cannot be moved from cell to cell, plant uses more ATP than produced in photosynthesis, ATP required for active transport
