A Level Biology Revision Notes

Comprehensive A Level Biology revision notes providing information and assistance for all UK examination boards (AQA, OCR, Edexcel) as well as international curriculum (CIE).

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Lipids are biological macromolecules made up of carbon, hydrogen and oxygen atoms. Lipids are also made up of a large group of heterogeneous compounds such as fats, oils, waxes, phospholipids and the derived lipids such as steroids. All these compounds are insoluble in water, but they dissolve in the nonpolar solvents such as benzene and carbon tetrachloride.

A cell is the basic fundamental unit of all life on Earth. It contains numerous important structures and components that function together, with all the parts interacting with each other. The cytoplasm is the intracellular space within the cell containing all these structures and components.

Biochemical reactions necessary for growth, repairing damaged tissues, and obtaining energy take place in all living organisms’ bodies. These reactions are called metabolism and they continue in all living organisms. If they stop working, this leads to death of the organism.

All the reactions occurring in living organisms require high activation energy to take place. To reduce the cell consumption to more energy, there should be a catalyst to be sure that the chemical reaction occurs rapidly throughout reducing the activation energy. This catalyst is the enzymes.

You know that the structure of living organisms comes in gradual levels. These levels begin with the systems, organs, tissues, cells and finally come the organelles. If we follow up this structural sequence of living organisms, we will find that the cells of any living organism are made up of organic and inorganic molecules and each of these molecules is made up of atoms as well.