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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Protein Structure

Proteins represent the structural composition of all living organisms. All living organisms from the hugest animal to the extremely microscopic one are mainly made up of proteins. Proteins contribute to the biochemical processes preserving the life.


In cellular biology, osmosis refers to the collection of mechanisms that regulate the passage of solutes such as ions and small molecules through biological membranes, which are lipid bilayers that contain proteins embedded in them.


Carbohydrates are biological macromolecules made up of smaller molecules called monomers. Carbohydrates include sugars, starches and fibers. They are symbolized by the formula (CH2O)n. According to this formula, carbohydrates are made up of carbon (C), hydrogen (H) and oxygen (O) atoms in the ratio 1:2:1.

Calculating Magnification and Size

The progression of biology is thoroughly based upon the development of the technologies used in the science field related to the cell science (Cytology). This development has leaded to increase the ability of scientists to observe and analyze.

Lipids Structure and Function

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.

Fluid Mosaic Model

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.

Factors Affecting Enzyme Activity

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.

Enzyme Inhibitors

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.

Biological Molecules

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.