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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Photosynthesis

Photosynthesis Chloroplasts are large organelles, usually in a biconvex shape, and about 4-10μm long and 2-3μm wide. Within plants most chloroplasts are found in the mesophyll cells of leaves. The stages of photosynthesis take place within the chloroplast, stage 1 within the granum and stage 2 within the stroma. Stage 1 – Light Dependent Photosynthesis …

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Plant Reproduction System

When it comes to the plant reproduction system, the plant kingdom showcases an astonishing diversity of reproductive strategies, each finely tuned to ensure the survival and proliferation of species. Unlike animals, plants are rooted in place, and as such, their reproduction has evolved to conquer the challenges of terrestrial life. From the simplicity of asexual …

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Phloem – Plant Tissue

Made up of 4 different parts: The sieve tubes and companion cells are both involved with the mass flow hypothesis. Sieve Tubes With the end of the sieve wall broken down, it allows inter-cellular movement. Translocation from Source (e.g. sugar in leaves) to Sink (roots) Osmotic Pressure The movement of solutes from a high hydrostatic …

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The Five Kingdoms Classification System

All living things can be grouped into five categories. This is called the five-kingdom proposal and was introduced by Robert Whittaker in 1968 as a way to categorise all organisms. Living organisms are divided into the five kingdoms: Prokaryotae Protoctista Fungi Plantae Animalia The vertebrate subsection of the animalia kingdom can be split again into …

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The Digestive System

The digestive system is a complex network of organs and tissues that work together to break down food into small molecules, absorb nutrients, and eliminate waste, and is essential for providing energy and nutrients to the body. Digestion is the breaking down of chemicals in the body to a form that can be absorbed and …

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Respiration

Respiration is a set of metabolic reactions and processes that take place within the cells of organisms. It stores biochemical energy within adenosine triphosphate (ATP) molecules. There are two types of respiration, aerobic and anaerobic. Respiration is also the process of making ATP rather than breaking it down. ATP (Adenosine triphosphate) ATP is the main …

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Biological Compounds

Introduction Carbohydrates are made up of monosaccharides – which are with relatively small molecules used as building blocks. As well as monosaccarides other monomers like amino acids and nucleotides are also used as building-blocks for the larger polymer structures. Polymers are the larger structures, built from monomers, and include carbohydrates, proteins and nucleic acids. The …

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Transport Methods – Movement across cell membranes

For more information on the cell membrane itself try the Cell Structure page. Diffusion Diffusion is the transport of molecules from a region of high concentration to a region of lower concentration. The rate of diffusion depends upon: Concentration Gradient – the higher the concentration gradient between the two regions the faster the rate of movement. Distance …

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Cell Structure – Plant & Animal Cell

Plasma Membrane The plasma membrane is a thin, permeable membrane which surrounds the cell. It controls any exchange in or out of the cell. The fluid mosaic model was suggested by S. J. Singer and G. L. Nicolson in 1972. They believed that the plasma membrane around cells was made up from a phospholipid bilayer. …

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Disease – Bacterial, Viral & Protoctistan

Bacterial Diseases Salmonella Salmonella is a type of bacteria usually found within poultry eggs, unprocessed milk, meat and water. It is a rod-shaped gram-negative enterobacteria that causes typhoid fever. It was discovered by an American scientist named Dr. Daniel Salmon. It can cause: Every year approximately 40,000 cases of salmonella are reported. It can be …

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