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Biological Molecules    Cell Structure    Cell Transport    Immunology    Exchange    Mass Transport    DNA, Genes & Protein Synthesis    Genetic Diversity    Biodiversity    Photosynthesis    Respiration    Energy & Ecosystems    Stimuli and Response    Nervous Coordination & Muscles    Homeostasis    Inheritance    Populations & Evolution    Ecosystems    Gene Expression    Recombinant DNA Technology   


Carbohydrate is a polymer made from monomers (building blocks) called monosaccharides. Dissacharides and polysaccharides are formed from monosaccharides through condensation reactions, in which the reverse is hydrolysis. Examples of polysaccharides include starch, glycogen and cellulose.

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Fats are lipids, which are split into two groups: Triglycerides and phospholipids. Triglycerides are mainly used for enegry storage and contains 3 fatty acids with a glycerol molecule. On the other hand, phospholipids have one of the fatty acids replaced by a phosphate group. Phospholipids are crucial due to them forming the sturcture of cell membranes. Its hydrophobic nature of its tails creates a phospholipid bilayer - the main structure of the membrane.

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Proteins are crucial for the body's muscle recovery, metabolism, enzymatic reactions and immune response. It is composed of monomers (building blocks) called amino acids. Amino acids join together under condensation reactions to form dipeptides and polypeptides, in which its reverse process is named hydrolysis. Protein's primary, secondary, tertiary and quaternary sturctures help form its overall 3D shape which correlates to its function. Bonds like hydrogen, ionic, covalent and disulfide bridges help contribute to the overall folding process of the protein.

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Enzymes are biological catalysts that speed up reactions without being used up. Throughout the years, the lock and key model for enzyme action has been adapted, however, recently, the induced fit model is more accurate. Within in the induced fit model, we describe enzymes' active site as being flexible and will adapt and change shape to allow substrate to bind to the enzyme. This is due to bonds within the active site breaking and reforming in order to form an ezzyme-substrate complex.

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Factors Affecting Enzymes

There are various factos the affect and change enzyme catalysation rate: Temperature, pH level, substrate concentration and enzyme concentration. In addition, enzyme inhibitors are molecules that directly or indirectly change the shape of the active site of the enzyme to prevent the enzyme functioning as normal.

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DNA stores genetic information needed for growth and protein synthesis, in which RNA contributes to this process by copying genetic information from the DNA in the nucleus to the ribosomes for translation. DNA and RNA are polymers of nucleotides, which contains a phosphate group, a pentose sugar and one of 4 bases: Adenine, Thymine, Cytosine and Guanine (thymine is replaced by uracil in RNA).

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DNA Replication

DNA Replication is a part of the cell cycle as DNA must be replicated before the nucleus divides. The enzyme DNA helicase breaks the hydrogen bonds causing the double helix to unwind. Complimentary free nucleotides are then binded and the new strands of the nucleotides are joined together by enzyme DNA polymerase. Finally, each new DNA molecule contains one strand from the original and one from the new strand.

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ATP stands for adenosine triphosphate. It is crucial as it is a product of respiration and releases energy from glucose for many biological processes to occur. Under the enzyme ATP hydrolase, ATP is broken down into ADP and inorganic phosphate. The broken phosphate bond then releases energy. On the other hand, the reverse process is known as ATP Synthesis and is catalysed by the enzyme ATP synthase.

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Water is an essential biological molecule for making up cells, being a metabolite, a solvent and a habitat for many organisms. The polar nature of water (due to having a slightly negative charge on one side and positive on the other due to electron configurations) causes water to be a great solvent. Water's high latent heat of vaporisation and heat capcity also allows them to be great at temperature control. The cohesive nature of water (high attraction between individual water molecules) makes water flow and supports columns in xylem cells of plants.

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Inorganic Ions

Many inorganic ions contribute to metabolic processes within the body. For example, calcium ions are used in the transmission of action potentials and sodium ions are used to carry glucose or amino acids into the epithelium of the ileum along a carrier protein.

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Biochemical Tests

Tests are carried out to test for the presence of biological molecules. The biuret test is used to test for proteins; the Benedict's test is used to test for carbohydrates; anhydrous cobalt(II) chloride paper is used to test for water; the emulsion test is used to test for lipids.

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