biology paper 1

• Nucleus


  Stores DNA and directs all cellular activities
• Cell membrane


  Holds the cell together and controls what goes in and out
• Mitochondria


  Powerhouse of the cell where aerobic respiration takes place
• Ribosomes


  Site of protein synthesis
• Cell wall


  Found on the outside of plant cells, it is made of cellulose and strengthens the cell
• Permanent vacuole


  Found in plant cells, it helps support the cell
• Chloroplasts


  Site of photosynthesis
• Not all plant cells have chloroplasts
• Types of cells


  • Prokaryotic
  • Eukaryotic
• Prokaryotic cells


  • Smaller, do not contain a nucleus, genetic material is in a single DNA loop, contain small rings called plasmids
• Eukaryotic cells


  • Plant, animal and fungal cells
• Bacterial cell


  Cytoplasm which takes over job of mitochondria and chloroplasts, may have a flagella, plasmids are present
• There are 1,000,000 micrometers in a meter
• Light microscope


  Microscope that uses a series of glass lenses and visible light to magnify an image, magnifies up to 1,000 times
• Electron microscope


  Microscope with high magnification and resolution, employing electron beams instead of light and using electron lenses
• Magnification


  Formula: Magnification = image size / real size
• Cell division


  Process by which a cell divides into two new daughter cells
• Chromosomes


  Found in the nucleus of a cell
• Humans have 46 chromosomes (23 pairs)
• Before cell division, the cell copies all of its DNA
• Stem cells


  Undifferentiated cells
• Embryonic stem cells


  Stem cells from early human embryos
• Plant stem cells


  Found in meristems
• People are concerned about using stem cells from cloned embryos due to viral infection and religious/ethical objections
• Diffusion


  The movement of particles from an area of high concentration to an area of low concentration
• Diffusion happens because the particles move randomly and spread out
• Factors affecting rate of diffusion

  • Concentration gradient
  • Thickness of exchange surface
  • Surface area
  • Temperature
• Osmosis


  Diffusion of water across a partially permeable membrane
• Active transport


  Movement of substances against a concentration gradient from a low area to a high area of concentration
• Processes allowing molecule movement

  • Diffusion
  • Osmosis
  • Active transport
• Processes involving movement down a concentration gradient

  • Diffusion
  • Osmosis
• Processes involving movement of water

  • Osmosis
• Processes needing energy from respiration


  • Active transport
• Specialised cells


  Cells that carry out a specific function
• As a cell differentiates, it may change shape and different sub-cellular structures develop to let it carry out a specific function
• Organ


  Tissues working together to perform a specific job
• Organ system


  A group of organs that work together to do a particular job
• Enzymes


  Biological catalysts that speed up reactions in living organisms
• Lock and key theory

  An enzyme and corresponding active site are exactly complementary
• Digestive enzymes


  • Amylase and lipase