Paper 2 - Respiration Flashcards
Structure of a mitochondria
Outer membrane
DNA
Ribosomes
Crista (fold in inner membrane)
Stalked particles (ATP synthase)
Matrix
Where does glycolysis occur?
In the cytoplasm -. Glucose is too big to cross mitochondrial membrane.
Stages of glycolysis
Phosphorylation - Glucose is phosphorylated using an ATP producing 2 x triose phosphate molecule
Oxidation - TP is oxidised and becomes 2 x pyrurate molecules
Hydrogen is released from TP is used to reduce NAD → NADH is formed
4 ATP is produced by substrate level phosphorylation (net gain = 2 x ATP)
Aerobic respiration - Kreb’s cycle
- Oxaloacetate binds with acetyl from acetyl CoA → citrate is formed
- Coenzyme A returns to link reaction
- Citrate is decarboxylated and oxidised → producing a 5C compound, CO2 and NADH
- The 5C compound is further decarboxylated and oxidised so oxaloacetate is reformed → CO2, NADH and FADH is produced
- ATP is produced by substrate - level phosphorylation.
Aerobic respiration - oxidative phosphorylation
- NADH or FADH release hydrogen splits into protons and electrons
- Electrons passed along ETC releasing energy
- Energy used to create proton gradient across inner mitochondrial membrane
- Protons move down electrochemical gradient back into the matrix via ATP synthase enzyme, providing energy for ADP + Pi → ATP
- Oxygen is the final electron acceptor - it combines with protons and electrons to form water
Anaerobic Respiration - Animal Cells
- Pyruvate produced from glycolysis is reducing using NADH
- NAD is regenerated and produces lactate = muscle fatigue
Anaerobic Respiration - Plant and Yeast cells
- Pyruvate produced from glycolysis is decarboxylated using CO2 and ethanal.
- Ethanal is reduced using NADH
- NAD is regenerated and produces ethanol.
- Ethanol and CO2 is produced - used in fermentation to produce beer
Required Practical 9 : The effect of a variable on the rate of respiration of cultures of a single - celled organism
METHOD
- Set up a water bath at 35 degrees
- Add 5cm3 of the yeast and glucose solution to 3 test tubes. Then place test tubes in the water bath, leaving the solution to equilibrate for 10 minutes.
- Add 2cm3 of methylene blue to test tubes and start the timer. Share for 10 seconds and place test tubes back in water bath.
- Record how long it takes for methylene blue to turn colourless for each test tube.
- Repeat the experiment using temperatures of 40 - 70 degrees range.
- Find the mean for each temperature and use to calculate the average rate of respiration
Required Practical 9 : The effect of a variable on the rate of respiration of cultures of a single - celled organism
CONTROL VARIABLE
The yeast and glucose solution should be buffered to maintain a constant pH
Required Practical 9 : The effect of a variable on the rate of respiration of cultures of a single - celled organism
HOW TO CALCULATE RATE OF RESPIRATION
Rate of respiration = 1/ mean time
Required Practical 9 : The effect of a variable on the rate of respiration of cultures of a single - celled organism
HAZARDS
DCPIP, biohazard, broken glass, hot liquids - similar to RP 8
Required Practical 9 : The effect of a variable on the rate of respiration of cultures of a single - celled organism
CONCLUSION
As the temperature moves away from the optimum for yeast, the rate of reaction will decrease as enzyme action decreases. At high temperatures denaturation may occur.
Rate of respiration also decreases meaning the methylene blue will take longer to turn colourless when the temperature is further from the optimum.
Aerobic respiration - The Link Cycle
- Pyruvate is actively transported into the matrix of the mitochondria
- Pyruvate is oxidised to acetate
- The hydrogens are used to form NADH
- Pyruvate is decarboxylated - loses CO2 molecule
- Acetate combines with coenzyme A to produce acetylcoenzyme A
