Cellular Respiration

2.8 Cell Respiration

Essential Idea:

Cell respiration supplies energy for the functions of life.

--> Cellular respiration is the gradual and controlled release of energy by breaking down organic compounds to produce ATP


Cell respiration is the controlled release of energy from organic compounds to produce ATP

==> Adenosine Triphosphate:


ATP from cell respiration is immediately available as a source of energy in the cell

What do we need energy for?

Parts of respiration:

1) Glycolysis

2) Krebs cycle

3) Electron transport chain & oxidative phosphorylation

Cellular respiration involves enzymes that control the process to ensure that energy is produced when it is required.


Two main ways of respiration:

Cell respiration can take place with or without the presence of oxygen. This leads to these two types:

1) Anaerobic respiration = no oxygen

2) Aerobic respiration = oxygen


Anaerobic cell respiration gives a small yield of ATP from glucose.

==> Yeast respires anaerobically to produce ethanol and CO2 when fermenting raw ingredients
==> CO2 produced by yeast is used to make bread rise, while the ethanol is evaporated away during baking
==> Also used to produce Bioethanol 

Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose


Glucose + Oxygen --> Carbon Dioxide + Water +Energy 


Respiration in sports:



A respirometer is a simple apparatus that can measure the rate of respiration. Cellular respiration uses oxygen and produces carbon dioxide and water. We can measure the consumption of oxygen as an indication of the respiration rate.

In Tube A, the organism to be tested (or germinating seed) is positioned, and the tap is closed. The organism starts respiring, consuming O2 and producing CO2 and H2O. The alkaline solution at the bottom of Tube A will absorb the CO2. Tube B is the control where no O2 is used or CO2 produced because no living organism is present. The capillary connecting the two tubes is a manometer.

The reduction in oxygen in Tube A will reduce the pressure in Tube A and will move the coloured liquid in the manometer in the direction of Tube A, providing an indirect measurement of the oxygen consumed, allowing the rate (amount of oxygen consumed per time unit) to be calculated.

Examples of investigations with respirometer: Compare the respiration rate of different organisms; The effect of temperature on respiration rate; Respiration rates could be compared in active and inactive organisms…


Continuation in 8.2


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