Nat 5 Biology - Unit 1

• Cell Wall


  Maintains cell shape, made of cellulose in plant cells, bacteria and fungal cells have a different structure.
• Cell membrane


  Is selectively permeable. It is made of proteins and phospholipids. It controls the entry and exit of substances in and out of the cell.
• Nucleus


  Controls all of cell activities. It contains chromosomes which carry the genetic information.
• Cytoplasm


  The site of chemical reactions. Contains enzymes.
• Vacuole


  Membrane bound organelle containing cell sap.
• Mitochondria


  Membrane bound organelle found in all cells except bacteria. They are the site of aerobic respiration and produce ATP. Cells with a high energy demand have more of these eg. muscle cell and sperm
• Chloroplast

  Membrane bound organelle found in plant cells. Contain chlorophyll. The site of photosynthesis.
• Ribosome


  Small almost spherical structure found in the cytoplasm of all cells. Site of protein synthesis.
• Concentration gradient


  Different concentration of substances exciting between cells and their environment.
• Passive transport


  The movement of substances along the concentration gradient, from an area of high concentration to an area of low concentration without using energy eg. Diffusion
• Osmosis


  The movement of water molecules from an area of high concentration to an area of low concentration across a selectively permeable membrane.
• Active transport


  The movement of substances from an area of low concentration to an an of high concentration. Requires energy.
• Cell division


  Essential for growth and repair. The parent cell divides to produce two genetically identical cells. If becomes uncontrolled it can cause cancer.
• Mitosis


  The division of the nucleus.
• Chromosomes


  Thread-like structures found in the nucleus. Contain genetic information which controls cell activities. Made of DNA
• DNA


  Made of two backbones to which bases are attached. The bases are A, C, T, G. The bases fit together in a particular way; A to T and C to G. This is called complementary base pairing. These strands twist and form a double-stranded helix.
• mRNA


  Made in the nucleus by copying the genetic code for a gene and carries this copy to a ribosome.
• Protein


  Made from amino acids. Joined together by polypeptide chains. Have a complex shape. The shape determines it's function.
• Enzymes


  Biological catalysts which speed up vital chemical reactions.
• Hormones


  Chemical messengers which help control the body's systems eg. Insulin
• Structural proteins


  The building blocks which form cells, organs and tissues eg. Keratin.
• Antibodies


  Produced by white blood cells to defend the body against viruses and unwanted bacteria.
• Receptors


  Found in membranes of cells. Receive signals from molecules outside the cell and pass them across the membrane into the cell.
• Degradation reaction


  Large substrate broken down into smaller product.
• Synthesis reaction


  Small substrate built up to make a larger product.
• Genetic engineering


  A technology that allows scientists to transfer DNA from one organism to another.
• Photosynthesis


  A series of enzyme controlled reactions using the raw products, carbon dioxide and water to form glucose and oxygen. Green plants use this process to make their own food.
• Respiration


  Chemical energy released by all cells through a series of enzyme controlled reactions. Glucose and oxygen to form carbon dioxide, water and ATP