Topic 14 - Respiration Flashcards
What is glycolysis?
First stage of aerobic respiration and anaerobic respiration.
Doesn’t need oxygen - anaerobic.
Occurs in cytoplasm of all living cells.
What is the summary of glycolysis?
Begins with activation of main respiratory substance - glucose.
The activation involves addition of 2 phosphate groups provided by 2 ATP.
Produces phosphorylated glucose, undergoes hydrolysis to produce 2x triose phosphate.
Molecules oxidised, oxygen removed transferred to NAD.
Production of 2x pyruvate, which also forms 4 ATP, so a net gain of 2 ATP.
What is the link reaction?
- Pyruvate produced in glycolysis oxidised to acetate.
- One of the three carbon atoms forms one molecule of CO2.
- Involved reduction of NAD to reduced NAD.
- Acetate combines with coenzyme A to form acetylcoenzyme A.
- This then enters the Krebs cycle.
What is the Krebs Cycle?
Acetylcoenzyme A produced by link reaction combines with oxaloacetate, releasing acetylcoA.
Produces citrate which enters Krebs Cycle.
In a series of oxidation-reduction reactions, the citrate is converted back to oxaloacetate.
What is the electron transport chain?
- Formation of ATP here is by oxidative phosphorylation.
- In presence of oxygen, energy is released to allow phosphorylation of ADP.
- Hydrogen atoms split into protons and electrons.
- ETC requires reduced NAD and reduced FAD, electron carriers, and oxygen to accept the electrons and protons at the end.
- Most energy is ultimately used to synthesise ATP, but some is ‘lost’ as heat.
1 molecule of reduced NAD produces 3 ATPs
1 molecule of reduced FAD produces 2 ATPs
How do you measure respiration?
Measure rate of exchange of oxygen and/or carbon dioxide.
1) Oxygen is taken up
2) Carbon dioxide is absorbed by potassium hydroxide.
3) Decrease in pressure in the capillary tubing.
4) Drop of coloured liquid moves towards organism.
Why is there a strip of filter paper in the potassium hydroxide solution?
Increases surface area for absorption of CO2.
Why is oxygen required in the electron transport chain and what molecule is it converted into?
- Terminal electron acceptor
- Converted into water
How does anaerobic respiration occur in plants and some microorganisms?
1) Pyruvate loses 1 CO2
2) Reduced NAD is oxidised.
3) One hydrogen is passed to pyruvate (reduced pyruvate).
4) Produces ethanol
Why do animals respire anaerobically?
Strenuous exercise leads to both aerobic and anaerobic respiration.
Respiration rate increases and we are unable to supply sufficient oxygen to respiring tissues.
This is because there is insufficient time for oxygen to reach respiring tissues.
Oxygen debt occurs.
How do animals respire anaerobically?
1) Glucose only partly broken down.
2) Reduced NAD is oxidised.
3) Each pyruvate receives 2 hydrogen atoms, so becomes lactate.
4) Lactate concentration increases.
5) NAD now available again to accept hydrogen, so glycolysis continues.
What are the consequences of anaerobic respiration for animals?
1) Lactate concentration increases.
2) Lowers pH, more acidic.
3) Proteins denature.
4) Requires much more glucose to provide same quantity of ATP so rate of glycolysis increases.
