Cell biology

• Eukaryotic cells


  Complex and include all plant and animal cells
• Prokaryotic cells


  Smaller and simpler cell e.g. bacteria

  Single celled organisms
• Plant cells


  Include a cell wall, vacuole, chloroplasts, nucleus, cytoplasm, cell membrane, mitochondria and ribosomes
• Animal cells


  Nucleus, cell membrane, cytoplasm, mitochondria and ribosomes
• Cell membrane


  holds cell together and controls what goes in and out
• Nucleus


  Contains genetic material
• Cytoplasm


  gel like substance where most chemical reactions happen
• Mitochondria


  Where most of reactions for aerobic respiration takes place
• Ribosomes


  where proteins are made in a cell
• Cell wall


  Supports and strengthens the cell
• Vacuole


  contains cell sap
• Chloroplasts


  where photosynthesis occurs
• Bacterial cell


  Contains a cell membrane, cytoplasm, cell wall, plasmids(small rings of DNA) and a circular strand of DNA
• Microscopy


  magnification= image size/real size
• Light microscopes


  Let us see individual cells and large subcellular structures

  Uses light and lenses
• Electron microscopes 


  Have a higher magnification, and higher resolution

  Uses electrons instead of light to form an image
• Microscopy RP

  1. Add a drop of water on the middle of a slide
  2. Use tweezers to peel off some epidermal tissue of an onion and place it into the water
  3. Add a drop of iodine solution to stain them
  4. Place a cover slip over it
• Cell differentiation


  When an object changes to become specialised for its job
• Sperm cells


  Gets male DNA to female DNA

  Has a long tail and a streamlined head to help it reach the egg

  Lots of mitochondria to provide energy
• Nerve cells


  Carry electrical signals from one part of the body to the other

  Long to cover more distance and have branched connections at their ends to connect to other nerve cells and form a network
• Muscle cells


  Contract quickly

  Long so have space to contract

  Lots of mitochondria to generate energy
• Root hair cells 


  Grow long hairs to give the plant a big surface area for absorbing water and mineral ions from the soil
• Phloem and xylem cells


  Transport substances like food and water around plants

  Long and joined end to end

  Xylem cells are hollow and phloem cells have few subcellular structures so things can flow through them
• Growth and DNA replication

  1. Grows and increases the amount of subcellular structures such as mitochondria and ribosomes
  2. It then duplicates its DNA and forms X-shaped chromosomes
• Mitosis

  1. Chromosomes line up at the centre and cell fibres pull them apart. The two arms go to opposite sides of the cell
  2. Membranes form around each of the sets of chromosomes- the nucleus has divided
  3. The cytoplasm and cell membrane divide The cell has now produced two new identical daughter cells
• Stem cells


  Embryonic stem cells can turn into any type of cell

  Can be used to replace faulty cells
• Stem cells in plants

  Found in meristems

  Creates clones of whole plants cheaply and quickly

  Grow more rare species

  Grow more desired features in plants
• Diffusion 


  The spreading out of particles from an area of high concentration to an area of low concentration
• Osmosis


  The movement of water particles across a partially permeable membrane from an area of high concentration to an area of low concentration
• Osmosis RP

  1. Cut a potato into identical cylinders and get beakers with different sugar solutions (one being pure water)
  2. Measure the mass of the cylinders and leave them for 24h in one of the beakers
  3. Take them out to dry with a paper towel and measure the mass again
• Active transport 


  When the diffusion of particles goes against the concentration gradient

  This happens in root hair cells and in our gut
• Exchange substances

  1. The job of the lungs is to transfer oxygen to the blood and remove waste carbon dioxide
  2. Contains millions of little air sacs called alveoli where gas exchange takes place
  3. Specialised to maximise the diffusion of oxygen and carbon dioxide (large surface area, moist lining for dissolving gases, very thin walls and a good blood supply)
• The villi

  1. Provide a big surface area so digested food is absorbed much quicker into the blood
  2. They have a single layer of surface cells and a very good blood supply to assist quick absorption