life science

• Organic compounds


  Contain the elements carbon (C), hydrogen (H) and often oxygen (O)
• Important organic compounds in living organisms


  • Carbohydrates
  • Proteins
  • Lipids (fats)
  • Nucleic acids
  • Enzymes
• Inorganic compounds


  Compounds that can contain any combination of elements, but they rarely contain hydrogen and carbon together
• Water


  The most important inorganic compound in living organisms
• Carbohydrates


  Main role is to provide energy in living organisms, also form structural components such as cell walls in plants
• Monosaccharides


  The simplest carbohydrates, for example glucose and fructose
• Disaccharides


  Form when two monosaccharides combine, for example sucrose
• Polysaccharides


  Formed by a large number of monosaccharides, for example starch and cellulose
• Lipids or fats


  Made up of three fatty acids and a glycerol molecule, supply energy to living organisms and also form structural components such as cell membranes
• Proteins


  Made up of large chains of amino acids, important in cell structure, such as cell membranes and cell functions, such as transport of substances and regulation of body processes
• Enzymes


  Specialised proteins that speed up chemical reactions, sensitive to temperature and pH
• Lock-and-key model


  Explains how enzymes work
• Nucleic acids


  Found in all cells, DNA is found in the nucleus, RNA occurs in the nucleolus, cytoplasm and on the ribosomes, play an important role in controlling a cell's structure and functions
• Vitamins


  Organic compounds required by animals in very small quantities to maintain healthy body functioning
• Shortages of vitamins in the diet


  Can lead to deficiency diseases, for example rickets is caused by a lack of vitamin D
• Water (H₂O)


  Makes up a large portion (60-70%) of the mass of cells and is required for many metabolic processes in plants and animals
• Minerals


  Inorganic compounds required by living things for normal growth, development and functioning
• Types of minerals


  • Macro-elements (needed in relatively large quantities by plants and animals)
  • Micro-elements (needed in relatively small quantities by plants and animals)
• Animals obtain minerals


  From the food they eat
• Plants absorb minerals


  From the soil through their roots
• Overuse of artificial inorganic fertilisers


  Breaks down the soil structure and can lead to eutrophication of water bodies
• All living organisms are made of cells
• Cells


  Very small, need to use magnifying instruments like lenses and microscopes to view them
• Light microscope


  Uses a beam of light focused by glass lenses
• Electron microscope


  Has a much higher magnifying power than light microscopes, uses a beam of electrons focused by electromagnets to magnify objects instead of light rays and lenses
• Robert Hooke used a light microscope to examine non-living cork cells


  1665
• Antonie van Leeuwenhoek was the first person to observe living cells using a microscope</b>
• Cell theory


  Developed from microscope studies of cells
• Cell structure


  Cells are surrounded by a cell membrane (and also a cell wall in plant cells), and they contain cytoplasm and organelles
• Cell membrane


  Made of proteins and phospholipids, controls which substances move in and out of the cell
• Fluid mosaic model


  Explains the structure of cell membranes
• Nucleus


  Consists of a nuclear membrane with nucleopores, chromatin material and the nucleolus, controls all the activities of the cell
• Mitochondrion


  Releases energy for the cell during respiration
• Ribosomes


  Important in protein production
• Cytoplasm


  Stores and circulates materials
• Endoplasmic reticulum


  Transports substances from one part of the cell to another
• Golgi body


  Secretes, packages and distributes materials around and between cells
• Vacuoles


  Used mainly for storage, plant cell vacuoles are large, animal cell vacuoles are small
• Lysosomes


  Found only in animal cells, their function is to destroy damaged, dead and foreign cells
• Cell walls


  Found only in plant cells, made mainly of cellulose, give cells their shape, and support and protect cells