INTEGRATED SCIENCE

• Cell organelle


  Structures found within cells that perform specific functions
• Cell organelles found in

  • Plant
  • Animal
• Plant cells have a very large vacuole
• Functions of the nucleus and the mitochondrion

  The nucleus controls cell activities

  The mitochondrion is the powerhouse of the cell where energy is produced during respiration
• Cytoplasm


  Jelly-like mass in which cell organelles are embedded, where most of the cell's chemical reactions take place
• Cells that do a lot of work

  Have a lot more mitochondria, for example muscle cells
• Nucleus


  Contains genetic material called chromosomes (Chromosomes consist of DNA which gives the organism its specific characteristics)
• Mitochondrion


  Described as the powerhouse of the cell because it is the site where energy is produced during respiration
• Cell wall


  Mainly made up of cellulose, gives the plant a fixed and relatively sturdy structure, prevents the plant cell from bursting
• Cell membrane


  Partially permeable barrier which controls the exchange of materials (for example, food or waste) between the cell and its environment
• Chloroplast


  Site where photosynthesis takes place, contains the pigment chlorophyll which gives plants their green colour
• Vacuole


  Site where water and other substances (including food or waste) are stored
• Ribosome


  The site where protein synthesis takes place, either attached to the endoplasmic reticulum or freely floating in the cytoplasm
• Differences between plant and animal cells

  • Plant cells have a rigid cell wall so little variation in cell shape, usually have chloroplasts, have a large central vacuole, and food is stored as starch

  Animal cells have no cell wall so more variation of cell shape according to function, have no chloroplasts, usually have small vacuoles or none at all, and food is stored as glycogen
• States of matter


  • Solid
  • Liquid
  • Gas
  • Plasma
• Plasma


  A hot, ionised gas that contains charged particles
• Plasma was identified by William Crookes in 1879
• Natural forms of plasma

  • Aurora Borealis (Northern lights)
  • Lightning
• Man-made forms of plasma

  • Fluorescent lights
  • Neon lights
• Plasma is not a state of matter that is commonly spoken about
• After a spacecraft has left the Earth's orbit it can travel on a very long journey using plasma (ion propulsion)
• Solid


  • Closely packed and arranged in a regular way
  • Keeps its own shape and volume
  • Strong interparticle force
  • Particles vibrate in a fixed position
• Liquid


  • Close together with random arrangement of the particles, may occur in clusters
  • Takes the shape of its container but keeps its volume
  • Moderately strong interparticle force
  • Particles can flow past each other
• Gas


  • Individual particles are far apart and randomly distributed
  • Takes the shape and volume of its container
  • Weak interparticle force
  • Particles move quickly and randomly
• Substances can exist in different forms of matter


  According to the amount of energy the particles possess
• Water can exist in all three states of matter at the same time
• Changing states of water


  1. Heating ice to liquid water

  2. Heating liquid water to steam (gas)

  3. Cooling steam to liquid water
• Changes which involve the process of melting or evaporation require an increase in heat energy, while the removal of heat is necessary for condensation and freezing to take place
• Sublimation


  When a solid changes directly to a gas, without passing through the liquid state
• Deposition


  The change from a gas directly to a solid
• Iodine and dry ice (solid carbon dioxide) are examples of solids that sublime
• Physical changes only involve changes in state, the end product looks the same as the original
• Chemical changes involve the rearrangement of atoms to form new substances with different properties
• Diffusion


  The net movement of particles from a region of high concentration (where there are relatively many particles) to a region of lower concentration (where there are relatively fewer or no particles) until they are evenly distributed
• Diffusion


  • Happens in gases and liquids
• Diffusion in gases


  • Using a coloured gas in a gas jar
• Diffusion in liquids


  • Placing coloured dye at the bottom of a beaker of water
• Concentration gradient


  A difference in concentration of particles across a barrier or membrane
• Diffusion across a cell membrane

  1. Particles diffuse from a region of higher concentration to a region of lower concentration

  2. Diffusion slows down or stops once the particles are evenly distributed

  3. Further movement of particles is facilitated by active transport
• As long as a concentration gradient is present, diffusion will take place