1. Living Cells
Respiration
Mr G Davidson

2. Energy in Food Food is a source of energy for all organisms.
This energy is measured in Joules (J) or kilojoules (kJ). (1000J = 1kJ)
We can measure the amount of energy in a foodstuff by using it as an energy source to heat a known volume of water and measuring the rise in temperature.
Monday, February 25, 2019
Mr G Davidson

3. Energy in Food Thermometer We need to know the starting temperature
of the water and the
finishing temperature
of the water. This allows
us to calculate the rise
in temperature. We also
need to know the mass
of the food we are burning.
Known volume
of water
Burning Food
Monday, February 25, 2019
Mr G Davidson

4. Energy in Food
Once we have carried out the experiment, we should be able to fit the results into the following equation.
M= mass of water (g)
T= rise in temperature (oC)
Energy (kJ) = 4.2 x M x T
1000
Monday, February 25, 2019
Mr G Davidson

5. Energy in Food
The 4.2 comes from:- it takes 4.2 kJ to raise 1kg of water by 1oC, e.g.
If using a peanut weighing 2g to heat 50g water from 20oC to 58oC, we would enter the following.
M=50
T= 58-20= 38
So: 4.2 x 50 x 38 = 7.98
1000
Monday, February 25, 2019
Mr G Davidson

6. Energy in Food We must remember that this number is for 2g of peanut.
Therefore, if 2g releases 7.98kJ of energy, then 1g of peanut releases 3.99kJ of energy.
These figures can be worked out more accurately using a food calorimeter.
The energy values are often displayed on the side of food packets.
Monday, February 25, 2019
Mr G Davidson

7. Respiration
Respiration is the chemical process in cells which releases energy from food.
Glucose is the main source of energy in cells and releases 17kJ per gram.
During respiration, glucose is broken down by enzymes in a series of biochemical reactions.
Monday, February 25, 2019
Mr G Davidson

8. Respiration During this process energy is released.
Some of this energy is transferred to other chemicals and some of this energy is lost as heat.
In some organisms, this heat energy is essential if the organism is to maintain a constant temperature.
Monday, February 25, 2019
Mr G Davidson

9. Adenosine Tri-phosphate (ATP)
An adenosine tri-phosphate molecule consists of adenosine attached to three inorganic phosphate molecules. Pi Pi Pi
ADENOSINE
Monday, February 25, 2019
Mr G Davidson

10. Adenosine Tri-phosphate (ATP)
ATP is made using adenosine diphosphate (ADP), which contains two inorganic phosphates, and adding another inorganic phosphate.
ADENOSINE Pi Pi
Adenosine diphosphate
Inorganic phosphate
Monday, February 25, 2019
Mr G Davidson

11. ATP
When the energy is released from glucose, some of it is used to join the inorganic phosphate to the ADP to make ATP.
High energy bond
ADENOSINE Pi Pi
Inorganic phosphate
Adenosine diphosphate
Monday, February 25, 2019
Mr G Davidson

12. ATP
The energy used to join the phosphate to the ADP is stored in a high energy bond.
This energy is now available for a quick release as and when the cell needs it.
The high energy bond is broken and the stored energy is released.
Monday, February 25, 2019
Mr G Davidson

13. ATP
When energy once again becomes available to the cell the ADP and P are put back together to make ATP.
This build up of ATP is called PHOSPHORYLATION.
Energy released
ATP
ADP + Pi
Energy used up
High
energy
compound
Low
energy
compound
Monday, February 25, 2019
Mr G Davidson

14. Chemistry of Respiration
Respiration is the process which releases chemical energy from glucose.
Respiration occurs in ALL living cells.
When there is an ample supply of oxygen it is called aerobic respiration.
Respiration builds up ATP molecules.
Monday, February 25, 2019
Mr G Davidson

15. Glycolysis
A 6-carbon glucose molecule is broken down by a series of enzyme controlled reactions into two 3-carbon molecules of pyruvic acid.
This process is called glycolysis and does not require oxygen.
It also releases enough energy to regenerate 2 molecules of ATP.
Monday, February 25, 2019
Mr G Davidson

16. Glycolysis Pyruvic acid Glucose Pyruvic acid 2 ADP + Pi 2 ATP
Monday, February 25, 2019
Mr G Davidson

17. Chemistry of Respiration
Pyruvic acid still contains a lot of energy and is now broken down even further by enzymes in the presence of oxygen.
Each pyruvic acid is broken down to carbon dioxide and water, and this releases enough energy to make 18 molecules of ATP.
Monday, February 25, 2019
Mr G Davidson

18. Chemistry of Respiration
This means a total of 36 ATP molecules are produced from the two pyruvic acid molecules.
If this is added to the 2 molecules of ATP produced in glycolysis it means that one molecules of glucose can release enough energy to regenerate a total of 38 ATP molecules.
Monday, February 25, 2019
Mr G Davidson

19. Chemistry of Respiration
18ADP + Pi
18ATP
Carbon dioxide
+ Water
Pyruvic acid
Glucose
2 ADP + Pi
+ OXYGEN
2 ATP
Carbon dioxide
+ Water
18ADP + Pi
18ATP
Monday, February 25, 2019
Mr G Davidson

20. Anaerobic Respiration
Anaerobic respiration occurs when there is no oxygen.
It involves the partial breakdown of glucose.
Glycolysis occurs as normal, releasing its 2 ATP molecules.
Monday, February 25, 2019
Mr G Davidson

21. Anaerobic Respiration
However, the pyruvic acid is converted to other molecules depending on whether the organism is a plant or an animal.
In animals pyruvic acid is converted into lactic acid.
Monday, February 25, 2019
Mr G Davidson

22. Anaerobic Respiration
This lactic acid can be converted back to pyruvic acid when oxygen becomes available.
Lactic acid results in muscle fatigue which reduces the efficiency of the muscle cells, and eventually leads to cramp.
Monday, February 25, 2019
Mr G Davidson

23. Anaerobic Respiration
During periods of anaerobic respiration an oxygen debt builds up, and this oxygen must be repaid to convert the lactic acid back to pyruvic acid.
This makes anaerobic respiration in animals a reversible process.
Monday, February 25, 2019
Mr G Davidson

24. Anaerobic Respiration in Animals
Glucose
2 ADP + Pi
2 ATP
Pyruvic acid
Recovery
period
Vigorous
exercise
+ OXYGEN
Lactic acid
Monday, February 25, 2019
Mr G Davidson

25. Anaerobic Respiration in Plants
Anaerobic respiration in plants and yeast results in pyruvic acid being converted to ethanol and carbon dioxide.
The carbon dioxide is released as a waste product, and this makes anaerobic respiration in plants an irreversible process.
Monday, February 25, 2019
Mr G Davidson

26. Anaerobic Respiration in Plants
Glucose
2 ADP + Pi
2 ATP
Pyruvic acid
Ethanol +
Carbon dioxide
Monday, February 25, 2019
Mr G Davidson