cells and movement between membranes

• Nucleus


  Stores DNA & controls cell activities
• Cytoplasm


  Site of cell reactions
• Cell membrane


  Controls entry and exit of substances
• Mitochondria


  Carry out respiration to release energy
• Eye piece lens


  Fixed magnification (zoom)
• Objective lenses


  Different magnifications (x4, x10, x40)
• Coarse focus


  Roughly focuses the image
• Fine focus


  Make the image as focused as possible
• Slide


  Glass which holds the specimen to view
• Stage


  Where the slide is placed
• Cell wall


  Supports the cell
• Chloroplasts


  Carry out photosynthesis
• Vacuole


  Maintains cell shape
• Method to view cheek cells

  1. Put methylene blue onto glass slide

  2. Gently rub inside of cheek with cotton bud & spread onto the methylene blue, then place the used cotton bud in disinfectant

  3. Gently lower coverslip on top of the slide using a mounted needle

  4. View using x10 objective lens & then x40 objective lens on a light microscope
• Method to view onion cells

  1. Pull a thin layer off an onion using forceps (tweezers) & spread onto a glass slide

  2. Add iodine

  3. Gently lower coverslip on top of the slide using a mounted needle

  4. View using x10 objective lens & then x40 objective lens using a light microscope
• Light microscopes have limited magnification (don't zoom in very much). Electron microscopes can have much higher magnifications.
• Electron microscopes have some disadvantages though: Can only view dead cells
• Differentiation


  The specialisation of a cell into a specific type of cell
• Specialised cells


  Cells which have features that suit their function
• example of specialised cells are Red blood cells

  • No nucleus - more space for haemoglobin
  • Biconcave shape- increasing surface area to transport more oxygen
• example of specialised cells are Root hair cells

  • Many mitochondria for active transport of minerals
  • Large surface area to absorb more water via osmosis
• Light microscopes have limited magnification. Electron microscopes can have much higher magnifications.
• cytoplasm 


  site of cell reactions
• nucleus 


  control cell activities and store DNA
• magnification of drawing 


  drawing size / irl size
• Levels of biological organisation

  • Cell
  • Tissue
  • Organ
  • Organ system
  • Organism
• Tissue


  groups of similar cells with a similar function
• Organ


  several tissues performing specific functions
• Organ system


  Group of organs working together to carry out specific functions, e.g. digestive system, respiratory system
• Organism


  The whole living thing, made of multiple organ systems, e.g. human, ant, oak tree
• Enzymes


  Small proteins made by cells & are catalysts (speed up reactions, without being used up) & can break down or build up substrates
• Lock & key model

  Substrate fits into an enzymes' specifically shaped active site to form an enzyme substrate complex & the substrate gets changed into products
• Increasing temperature effect on enzymes


  Increases kinetic energy, more enzyme substrate complexes → more product formed more quickly
• Optimum temperature

  Highest rate of enzyme reaction
• If too hot enzymes will ...

  The enzyme denatures (active site changes shape) & the substrate can't fit into the active site → no enzyme substrate complexes → no product formed
• Optimum pH

  Highest rate of enzyme reaction
• If pH too acidic or too alkali, enzyme will .. 


  The enzyme denatures (active site changes shape) & the substrate can't fit into the active site → no enzyme-substrate complexes → no product formed
• Diffusion

  Passive, movement of particles from a high concentration to a low concentration
• Factors that increase diffusion

  • Large concentration gradients
  • High temperature
  • High pressure
• Osmosis


  Passive, movement of water particles from a high concentration to a low concentration, across a semi-permeable membrane