Biology

• Mitochondria


  Provides energy for respiration
• Stomata


  Pores in the epidermis of leaves that allow gas exchange
• Specialised cells and their functions

  • Ciliated cells - movement of mucus in the trachea and bronchi
  • Root hair cells - absorption
  • Palisade mesophyll cells - photosynthesis
  • Neurones - conduction of electrical impulses
  • Red blood cells - transport of oxygen
  • Sperm and egg cells (gametes) - reproduction
• Cell


  Smallest unit of life
• Tissue

  Group of cells with similar structure and function
• Organ


  Structure made up of different tissues working together
• Organ system

  Group of organs working together to perform a specific function
• Organism


  Living thing
• Calculating magnification

  Magnification = image size ÷ actual size
• Converting measurements

  Millimetres (mm) to micrometres (μm), value has to be multiplied by 1000
• Diffusion

  Net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient, due to random movement
• The energy for diffusion comes from the kinetic energy of random movement of molecules and ions
• Some substances move into and out of cells by diffusion through the cell membrane
• Importance of diffusion

  • Diffusion of gases and solutes in living organisms
• Factors influencing diffusion

  1. Surface area

  2. Temperature

  3. Concentration gradient

  4. Distance
• Osmosis

  Net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane
• Water diffuses through partially permeable membranes by osmosis
• Water moves into and out of cells by osmosis through the cell membrane
• Investigating osmosis


  Using materials such as dialysis tubing
• Investigating effects of solutions on plant tissues

  Immersing them in solutions of different concentrations
• Plants are supported by the pressure of water inside the cells pressing outwards on the cell wall
• Turgid, turgor pressure, plasmolysis, flaccid

  Effects on plant cells of immersing them in solutions of different concentrations
• Importance of water potential and osmosis

  • Uptake and loss of water by organisms
• Active transport


  Movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration, against a concentration gradient, using energy from respiration
• Importance of active transport


  • Movement of molecules or ions across membranes, including ion uptake by root hairs
• Protein carriers move molecules or ions across a membrane during active transport
• Chemical elements in biological molecules

  • Carbohydrates
  • Fats
  • Proteins
• Monomers and polymers

  Glucose to starch, glycogen and cellulose

  Amino acids to proteins

  Fatty acids and glycerol to fats and oils
• Tests for biological molecules

  Iodine solution for starch

  Benedict's solution for reducing sugars

  Biuret test for proteins

  Ethanol emulsion test for fats and oils

  DCPIP test for vitamin C
• DNA structure

  Two strands coiled together to form a double helix

  Each strand contains bases that pair up in a specific way: A with T, C with G
• Catalyst


  Substance that increases the rate of a chemical reaction without being changed by the reaction
• Enzymes

  Proteins that function as biological catalysts in all metabolic reactions
• Importance of enzymes


  • Reaction rate necessary to sustain life
• Enzyme action

  Active site of enzyme is complementary to its substrate, forming an enzyme-substrate complex that produces products
• Investigating effect of temperature and pH on enzyme activity

  Optimum temperature and denaturation
• Enzyme specificity

  Complementary shape and fit of active site with substrate
• Effect of temperature on enzyme activity

  Kinetic energy, shape and fit, frequency of effective collisions, denaturation
• Effect of pH on enzyme activity

  Shape and fit, denaturation
• Photosynthesis


  Process by which plants synthesise carbohydrates from raw materials using energy from light
• Word equation for photosynthesis


  Carbon dioxide + water → glucose + oxygen