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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Cell Signaling

In order to respond to changes in their immediate environment, cells must be able to receive and process signals that originate outside their borders. Individual cells often receive many signals simultaneously, and they then integrate this into a unified action plan. But cells aren’t just targets.: they also send out messages to other cells both …

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Carbohydrate Polymers

Summary If we follow the 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. Inorganic molecules in living organisms, such as water and salts, often do not contain carbon atoms. Organic …

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Structure of Collagen

Collagen is a member of a family of naturally occurring proteins. It is one of the most plentiful proteins present in mammals and it is responsible for performing a variety of important biological functions. It is most well-known for the structural role it plays in the body. It is present in large quantities in connective tissue and provides tendons and ligaments with tensile strength and skin with elasticity. It often works in conjunction with other important proteins such as keratin and elastin.

Organelle Structure and Function

The cell is the functional and building unit in all living organisms. These cells are characterized by their ability to grow, reproduce, respond to external stimuli and perform the different metabolic processes.

Nucleotides

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.

The Circulatory System

The circulatory system consists of the heart and the blood vessels through which the blood passes. These vessels form a complete circuit. (A closed circulatory system).

Amino Acids

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.

Structure of the Heart

The heart is a hollow muscular organ which lies in the middle of the chest cavity. It is enclosed in the pericardium that protects the heart and facilitates its pumping action. It is divided into four chambers.

Structure of DNA

By the early 1950’s there was strong evidence that DNA carries a cell’s genetic information of the cell and many people were trying to work out the structure of the DNA molecule and make a model of it.

Specialised Cells

Most living organisms are composed of several cells. But, are these cells irregular or disordered? Does each of them work separately from the other?