| Consequences of not enough O2 available for respiration | - No final acceptor of electrons from the ETC
- ETC stops functioning
- No more ATP is produced via OP
- NADH + FADH2 aren’t oxidised by an electron carrier
- No oxidised NAD + FAD are available for dehydrogenation in the KC
- The KC stops
- But still a way for cells to produce some ATP in low O2 conditions through anaerobic respiration |
| Anaerobic pathways | - Some cells are able to oxidise the NADH2 produced during glycolysis so it can be used for further H transport
- So glycolysis can continue + small amounts of ATP still produced
- Different cells use different pathways to achieve this
- Yeast + microorganisms use ethanol fermentation, pyruvate converted to ethanol + CO2
- Other microorganisms + mammalian muscle cells use lactate fermentation, pyruvate converted to lactate |
| Ethanol fermentation and lactate fermentation | - Pyruvate can be converted to ethanol or lactate using reduced NAD
- The oxidised NAD produced in this way can be used in further glycolysis |
| Ethanol fermentation word equation | pyruvate + reduced NAD ------> ethanol + CO2 + oxidised NAD |
| Metabolisation of lactate | After lactate is produced two things can happen:
- Oxidised back to pyruvate then channelled into the KC for ATP production
- It can be converted into glycogen for storage in the liver
- Oxidation of lactate back to pyruvate needs extra oxygen
- This extra oxygen is referred to as an oxygen debt
- It explains why animals breathe deeper and faster after exercise |
| Lactate fermentation word equation | pyruvate + reduced NAD -----> lactate + oxidised NAD |
| Energy yields from anaerobic respiration | - Pyruvate is converted to either ethanol or lactate
- Consequently it is not available for the KC, so neither the KC or the ETC can take place
- The only ATP that can be produced by anaerobic respiration is therefore formed by glycolysis |
| Investigating factors affecting respiration in single-celled organisms | - Yeast are single-celled organisms that can be grown in culture
- Can respire aerobically when plenty of O2 is available + anaerobically when O2 isn't available
- Both aero + ana resp. produce CO2 so the rate of CO2 production gives an indication of the yeasts respiration rate
- Measured using gas syringe |
| Investigating the effects of temperature on yeast respiration (aerobic respiration) (1) | - Put known vol. + conc. of substrate solution in test tube
- Add known vol. of buffer solution
- Place test tube in water bath
- Set 1 of the temps. being investigated
- Leave for 10 mins
- Add known mass of dried yeast, stir
- After yeast has dissolved, put bung with a tube attached to a gas syringe in the top of test tube |
| Investigating the effects of temperature on yeast respiration (aerobic respiration) (2) | - Gas syringe set at 0
- Start timer as soon as the bung has been put on tube
- As yeast respires, CO2 formed will travel up tube into gas syr.
- At regular time intervals, record vol. of CO2 in gas syringe
- A control experiment set up at each temp. where no yeast present, no CO2 should form without yeast
- Repeat experiment 3 times, calculate mean rate of CO2 production at each temp. |
| Investigating the effects of temperature on yeast respiration (anaerobic respiration) (1) | - Put known vol. + conc. of substrate solution in test tube
- Add known vol. of buffer solution
- Place test tube in water bath
- Set 1 of the temps. being investigated
- Leave for 10 mins
- Add known mass of dried yeast, stir
- After yest has dissolved, add liquid paraffin
- This will stop O2 getting in, forces yeast to respire anaerobically
- Put bung, with tube attached to a gas syringe, in the top of tube |
| Investigating the effects of temperature on yeast respiration (anaerobic respiration) (2) | - Gas syringe set at 0
- Start timer as soon as the bung has been put on tube
- As yeast respires, CO2 formed will travel up tube into gas syr.
- At regular time intervals, record vol. of CO2 in gas syringe
- A control experiment set up at each temp. where no yeast present, no CO2 should form without yeast
- Repeat experiment 3 times, calculate mean rate of CO2 production at each temp. |
| The rate of O2 consumption can be measured using a Respirometer | - Indicates rate of aerobic respiration by measuring amount of O2 consumed by an organism over a period of time |
| Investigation on the rate of O2 consumption using a Respirometer (1) | - Apparatus set up
- Partially submerged in water bath at 15 degrees to provide optimum temp. for woodlice (for enzymes)
- Control tube is set up in exactly the same way
- Except woodlice are replaced with glass beads of same mass |
| Investigation on the rate of O2 consumption using a Respirometer (2) | - For 10 mins, the tap is left open, syringe is removed to allow apparatus to equilibrate
- The respiration rate of the woodlice to stabilize in new environment
- After the 10 mins, tap is closed, syringe attached
- Syringe is used to reset the manometer
- Record vol. scale on the syringe
- As respiration occurs, air vol. of woodlice tube will decrease, due to O2 consumed in respiration |
| Investigation on the rate of O2 consumption using a Respirometer (3) | - This reduce the pressure in tube, causing colored fluid in the capillary tube of the manometer to move towards it
- Syringe used to reset manometer
- Record vol. scale on the syringe
- Difference between this figure + the other is the O2 consumed for this time period, used to cal. rate of respiration
- Repeat, cal. mean |
