DNA: DNA is a type of nucleic acid called deoxyribonucleic acid. It is a long chain molecule made up of nucleotides. One nucleotide is made up of: A 5 carbon sugar A phosphate group An organic base Nucleotides link together by condensation reactions between the sugar...
Genetic Screening: Genetic screening is used to: Identify carriers: heterozygotes with normal phenotypes. This can be followed up with counselling to help potential parents make a decision. Embryo testing: a sample of cells from a developing foetus can be analysed....
Movement across the plasma membrane: Osmosis: the movement of water molecules from high concentration to low concentration through a partially permeable membrane. Diffusion: the movement of molecules or ions from an area of their high concentration to an area of their...
Proteins: Structure of an amino acid: The amino acid monomers join together in a condensation reaction to form peptide bonds. The polymer formed is called a polypeptide. How do they form? Primary structure: the sequence of amino acids in the polypeptide chain. Amino...
Enzymes: Are globular proteins which act as catalysts. They speed up chemical reactions by lowering the activation energy, and remain unchanged at the end of the reaction. They provide an alternate reaction pathway, which requires less energy to start. Part of the...
Heart and Circulation: In small unicellular organisms, substances move around slowly by diffusion. Diffusion is too slow to move substances round the larger bodies of multicellular organisms. Thus has a circulatory system: substances are carried in blood pumped by a...
Cell Membrane: Cell membrane is made up of a phospholipid bilayer. The phosphate head of the phospholipid is a polar molecule and attracts water – it is hydrophilic. The fatty acid tails are non-polar and hydrophobic. In the cell membrane, the hydrophobic tails face...
Carbohydrates: They have a general formula: Cx(H2O)n Saccharides are made from sugar molecules that are made from combinations of the elements carbon, hydrogen, and oxygen only. They are used for: Fuels for respiration (glucose). Energy storage molecules (starch and...
Lipids: Triglycerides are either fats or oils. They are made from the elements carbon, hydrogen, and oxygen only. They are insoluble in water. Triglycerides are used for: Long term energy storage molecules Insulation Protection (pericardium) Buoyancy Synthesis of...
Water: Water molecules are non-linear and polar molecules because the H and O atoms are different in size and electronegativity. They form hydrogen bonds with other water molecules. Some properties include… Property Explanation Excellent solvent...