Cell Biology

• Prokaryotic cells -

  • have no nucleus
  • bacteria cells
• Eukaryotic cells -

  • have a nucleus
  • animal and plant cells
• magnification = image size / actual size
• Differentiation is the process by which a cell changes to become specialised for its job
• Examples of specialised cells -

  • Sperm cell - reproduction
  • Nerve cells - rapid signalling
  • Muscle cells - contraction
  • Root Hair cells - absorbing water and minerals
  • Phloem and Xylem - transporting substances
• Mitosis is the process of cell division that results in two identical daughter cells.
• mitosis -

  • DNA is spread out
  • before it divides the cell grows
  • the cell then duplicates
  • the two arms of each chromosome go to opposite ends of the cell
  • membranes form around each set of chromosomes, forming a nuclei
  • then the cytoplasm and membrane divide
  • two genetically identical daughter cells are produced
• diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration
• Osmosis is the movement of water molecules across a partially permeable membrane from an area of higher water concentration to an area of lower water concentration
• active transport is the net movement of particles from an area of low concentration to an area of high concentration
• organisms exchange substances with their environment, for example cells can use diffusion to take in substances they need and get rid of waste products
• Gas exchange in the lungs -

  • the lungs need to transfer Oxygen to the blood, and get rid of Carbon Dioxide
  • the lungs contain sacs called Alveoli
  • the Alveoli are specialised to maximise the diffusion of oxygen and carbon dioxide
• How the alveoli are specialised -

  • large surface area
  • thin walls
  • good blood supply
• Villi (inside the small intestine) have a large surface area to increase the rate of diffusion