1. Metabolism and Sources of Energy

2. Metabolism When we speak about metabolism what do we mean?
What kind of chemical reactions do you think take place in our bodies?
Growth (making proteins)
Response (nerve reactions)
Movement (energy needed from respiration)

3. Metabolism describes all the chemical reactions in our bodies
The way our metabolism functions is extremely important as our bodies need to have constant and stable conditions
The maintainance of stable conditions in our bodies is called homeostasis

4. What do you think would happen if…
There were no reactions to break down sugar in our blood
There were no reactions to build new tissues when we get damaged
There were no reactions to send signals to your brain that you are touching something hot

5. Learning check What is meant by metabolism?
Can you name some example of metabolism in the human body
What word describes the maintainance of reactions in our body?

6. Reactions that involve breaking big molecules into smaller molecules release energy and are called catabolic
Eg. Respiration
Reactions that involve making bigger molecules out of smaller ones molecules use up energy and are called Anabolic
Eg. Photosynthesis

7. Most reactions take place in a number of steps which need to be carefully controlled if the cell is to function properly
Enzymes are the most important controllers of cellular reactions

8. Learning check What does the term catabolic reaction mean?
What does the term Anabolic reaction mean?
Can you give an example of each type?
What molecules re responsible for controlling reactions in our body?

9. Sources of energy The main source of energy for all life is the sun
Certain pigments such as chlorophyll can absorb light

10. When they absorb light they use it to form the chemical bonds in bio molecules such as carbohydrates
Remember photosynthesis is the way plants make their own food (glucose-which is a carbohydrate)

12. Cellular Energy This is the energy released by the reactions in a cell
When bio molecules such as carbohydrates are broken down the bonds are broken and energy is released
Some of this energy is used by the cell and the rest is lost as heat

13. In Summary
Photosynthesis in Plants builds up molecules with energy rich bonds (glucose)
Respiration breaks down glucose and releases this energy from the bonds
This is how plants provide energy from the sun for everything else on earth!

14. Learning check What is the source of all energy on earth?
In cells where is this energy found?

15. Syllabus
You should be able to do the following for Ordinary level Cell Metabolism:
Define the term: metabolism.
State that solar energy is source of energy on Earth.
State that cellular energy sourced from chemical energy in ATP