17: Respiration Flashcards
What are the 4 stages of respiration?
- glycolysis
- link reaction
- krebs cycle
- oxidative phosphorylation
Describe the Glycolysis Reation:
Where does it take place?
- occurs in the cytoplasm of cell
- phosphorylation of glucose by ATP (2) makes glucose (6C) more reactive converting it to glucose phosphate (6C)
- glucose phosphate (6C) is split into 2 (3C) molecules called triose phosphate
- triose phosphate is oxidised into 2 molecules of pyruvate (3C), via the removal of a Hydrogen
- NAD (coenzyme) accepts the hydrogen and becomes reduced NAD (a coenzyme)
- 2 molecules of ATP are formed via substrate level phosphorylation for each pyruvate formed
What is the NET product of ATP in glycolysis?
Why can Glycolysis happen in anaerobic conditons?
- 2 (4 produced - 2 removed)
- there is absence of oxygen in this reaction
Describe the Link Reaction:
Where does it take place?
- pyruvate produced in glycolysis moves from the cytoplasm into the matrix of the mitochondria
- this is to maximise the number of pyruvate molecules in the matrix
- molecules of Pyruvate (3C) is oxidised to 2-carbon acetate
- hydrogen released is used to reduce NAD to reduced NAD
- CO2 molecule also released
- Therefore (2C) acetate combines with coenzyme A to form acetyl-coenzyme A
- acetyl-coenzyme A enters the Krebs Cycle
Describe the Krebs Cycle:
- Acetyl Coenzyme A (2C) reacts with 4 carbon compound to produce a 6 carbon molecule.
- coenzyme A is released to be reused in the link reaction
- via a series of oxidation reactions, the 4 carbon compound is reproduced from the 6 carbon compound
- 2 molecules of Carbon Dioxide are produced (2C)
- hydrogen atoms removed in oxidation reactions are used to reduce NAD + FAD into reduced NAD + reduced FAD
- as well as a single molecule of ATP being produced by substrate level phosphorylation
- the 4C compound reproduced via oxidation reactions is used to combine with acetyl-coenzyme A to begin the cycle again
in krebs cycle
How many molecules of ATP, reduced NAD & reduced FAD are produced per 1 molecule of glucose?
ATP: 2
Reduced NAD: 6 (3 per acetate)
Reduced FAD: 2 (1 per acetate)
Where does Oxidative Phosphorylation occur?
Describe Oxidative Phosphorylation:
- occurs on the inner mitochondrial membrane which folds to form cristae
- reduced coenzyme releases its hydrogen forming a proton + electron:
2H -> 2H+ + 2e- - the coenzyme returns to the matrix to pick up more hydrogen in the link reaction/krebs cycle
- this electron is passed along the electron transport chain in the inner mitochondrial membrane, in a series of redox reactions, releasing energy as it passes from one electron carrier to the next
- this energy is used to pump protons into the inter-membrane space
- the protons diffuse back into the matrix using ATP synthase enzymes
- energy released by the protons is used to combine ADP + Pi -> ATP (chemiomosis)
- Oxygen acts as the terminal electron acceptor in the electron transport chain, combining with an electron and a proton to make water
- Oxygen is essential to allow ATP to be produced by the electron transport chain and chemiosmosis, so the ATP is made by oxidative phosphorylation
What is the main function Anaerobic Respiration?
- the main function of anaerobic respiration is to regenerate NAD so that glycolysis can continue
- this allows small amount of ATP to be made in the absence of oxygen
Describe Animal Cell Anaerobic Respiration:
- glucose split into 2 x triose phosphate
- oxidised into 2 x pyruvate, Hydrogen released to reduce NAD -> reduced NAD
- pyruvate then converted to lactate
Why must Lactic Acid be removed?
- lactic acid produced is toxic
- reduced pH of cells + therefore affects enzyme activity
- in muscle cells it can cause fatigue and cramp
Describe Anaerobic Respiration in Plant Cells:
- glucose split into 2 x triose phosphate
- oxidised into 2 x pyruvate, Hydrogen released to reduce NAD -> reduced NAD
- pyruvate is reduced into ethanol and co2
How much ATP in anaerobic and aerobic respiration?
Anaerobic: 2
Aerobic: 38
How many reduced NAD, reduced FAD and ATP produced per molecule of glucose in aerobic respiration?
reduced NAD: 10
reduced FAD: 2
ATP: 38
How many ATP molecules can reduced FAD + reduced NAD form?
reduced FAD: 2
reduced NAD: 3
Why is there a difference in the number of ATP molecules produced in oxidative phosphorylation?
- reduced NAD releases its hydrogen earlier in the electron transport chain than reduced FAD
- some more energy is released per transport to each protein in comparison
- therefore, more protons are pumped through electron transport chain, and diffuse back through ATP synthase, so therefore more ATP molecules produced
