What is Metabolism?
The thousands of chemical reactions that occur constantly in each living cell is called cellular metabolism.
A biochemical pathway is a series of chemical reactions that take place in the normal operation of living things.
Metabolic reactions are controlled and regulated to:
- The rate of metabolism (metabolic rate) varies greatly among organisms.
A biochemical pathway is a series of chemical reactions that take place in the normal operation of living things.
Metabolic reactions are controlled and regulated to:
- maintain cell functions
- meet the energy needs of the cell.
How is metabolism controlled?
INTERNAL MEMBRANES
ENZYMES
There are many different enzymes that control metabolic reactions. Each has a specific job.
Definitions:
Types of enzymes:
- Compartmentalising a cell by having membrane-bound organelles creates specialised environments for specific functions.
- A large number of activities can occur at the same time in a very limited space and under different conditions e.g. plant can photosynthesise and respire.
- Chemical reactions in lysosomes break down compounds brought into the cell by using strong digestive enzymes in an acidic environment.
- Enclosing them in a membrane prevents them destroying the cell.
ENZYMES
There are many different enzymes that control metabolic reactions. Each has a specific job.
Definitions:
- Enzymes: proteins that act as catalysts within living things.
- Catalyst: a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.
Types of enzymes:
Catabolic enzymes: break substances down into smaller parts and release energy.
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Anabolic enzymes: build smaller substances into larger ones and use energy.
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Locations of Enzymes:
Intracellular enzymes occur inside cells. They speed up and control metabolic reactions.
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Extracellular enzymes are produced by cells They work outside the cell, e.g. digestive enzymes break down food in the small intestines
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Biochemical Pathways, Activation Energy & Enzymes
- Each step in biochemical processes is controlled by an enzyme.
- Without enzymes, the reactions in living things would happen so slowly that life would be maintained and the organism would die.
- Activation energy: the energy required to start a reaction.
- Enzymes bind to a molecule, or substrate, to modify it and thus lower the activation energy required to make it react.
You Should Now Complete:
Question Set 10.1 on p. 311.
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