CELLS + MICROSCOPES

• animal cell


  contains: nucleus, cell membrane, cytoplasm, mitochondria, ribosomes

  
• plant cell


  contains: cell membrane, cell wall, nucleus, mitochondria, ribosomes, cytoplasm, vacuole, chloroplast

  
• nucleus


  controls the cell
• cell membrane


  control the substances that leave and enter the cell
• cytoplasm


  chemical reaction and cell activity takes place here
• mitochondria


  site of aerobic respiration and respiration, releases energy
• ribosomes

  produces proteins
• chloroplast


  contains chlorophyll and site of photosynthesis
• cell wall


  maintains shape of cell, supports it
• vacuole


  contains cell sap
• eukaryotic cells


  conatins cell membrane, Dna in nucleus, more complex

  e.g. yeast, animal and plant
• prokaryotes


  usually unicellular, no nucleus - single loop of dna, small rings of dna - plasmids, smaller than eukaryotes
• resolution


  the degree to which it is possible to distinguish between two objects that are very close together
• high resolution


  sharp, clear image
• low resolution


  blurry, unclear image
• light microscope


  has a limited resolution, lower magnification, relatively cheap, uses light to form images
• electron microscope


  much higher magnification, higher resolution, can be used to study cells in much finer detail, uses a beam of electrons to form images, allow you to see subcellular structures
• magnification =


  size of image/ size of actual image
• mitosis


  a form of cell division which produces new body cells
• mitosis process


  1. replication of dna to form two copies of each chromosome and synthesis of new sub-cellular structures (e.g. mitochondria and ribosomes)
  2. nucleus divides
  3. cell divide in two

  
• sperm cell


  • fertilise the ovum (egg)
  • flagellum (tail) whips side to side to help move the sperm through water
  • the middle section full of mitochondria, transfer the energy needed for the tail to work
  • acrosome stores digestive enzymes for breaking down the layers of the ovum
  • a large nucleus contains the genetic material to be passed on

  
• muscle cell

  • contract and relax to allow movement
  • contain special proteins that slide over each other making the fibres contract
  • many mitochondria to transfer the energy needed for the cells to contract and relax

  
• nerve cell

  • carry electrical impulses around the body
  • have a long fibre so they can carry messages up and down the body over long distances

  
• red blood cell

  • transports oxygen around the whole body
  • contains no nucleus so it has more space to carry oxygen

  
• root hair cell


  • absorb mineral ions and water from the soil
  • have a large surface area to increase the rate of absorption
  • have a large vacuole that speeds up osmosis between the soil and root hair cell
  • many mitochondria that transfer the energy needed for the absorption

  
• palisade cell

  • enable photosynthesis in the leaf
  • it has a lot of chloroplasts to help trap light and make food

  
• stem cell


  an undifferentiated cell which is capable of becoming any type of specialised cell
• use of stem cells in animals


  treatment of diseases and conditions
• use of stem cells in plants

  produce clones of plants quickly

  
  

  rare species can be clones to protect from extinction
• diffusion

  the random movement of molecules from an area of high concentration to an area of low concentration

  
  

  particles move down the concentration gradient

  
  

  doesn't require energy
• osmosis


  osmosis is the movement is the diffusion of water molecules from low solute concentration of water to high solute concentration of water through a partially permeable membrane

  
  

  doesn't require energy
• dilute solutions


  have a higher concentration of water molecules
• concentrated solutions


  have a low concentration of water molecules
• partially permeable membrane


  has holes in it that permit water molecules through but are too small to allow larger molecules through

  
• pure, dilute, concentrated

  
• osmosis in animal cells

  • in dilute solutions, osmosis can cause cells (red blood) to swell up and burst (lysis)
  • in concentrated solutions, osmosis can cause red blood cells to shrink due to loss of water (crenation)
• isotonic solution


  any solution that has the same solute concentration and

  water concentration compared to body fluids. In an isotonic solution, no net movement of water will take place.
• hypotonic solution


  any solution that has a low solute concentration

  and high water concentration compared to body fluids. In hypotonic solutions, there is a net movement of water from the solution into the cells.
• hypertonic solution

  any solution that has a high solute concentration and

  low water concentration compared to body fluids. In a hypertonic solution, the net movement of water will be out of the cells and into the solution.
• active transport


  the movement of molecules against a concentration gradient, from an area of low concentration to an area of high concentration.

  The process requires energy (ATP).