Biology Year 10 GCSE

• Plant cells

  • Cell wall present
  • Chloroplast present
  • Large permanent vacuole present
• Animal cells

  • No cell wall
  • No chloroplasts
  • No permanent vacuole
• Parts of a cell

  • Cell membrane
  • Cytoplasm
  • Nucleus
  • Cell wall
  • Mitochondrion
  • Chloroplast
  • Vacuole
• Cell membrane

  Controls substances entering and leaving the cell
• Cytoplasm

  Where most chemical reactions take place
• Nucleus

  Contains chromosomes which carry genetic information and controls the activities of the cell
• Cell wall

  Contains cellulose; it supports the plant's structure
• Chloroplast

  Absorb light for photosynthesis
• Vacuole

  Space filled with cell sap (a dilute solution of sugars and mineral salts)
• Mitochondria

  Site of aerobic respiration
• Examination of cheek cells using a light microscope

  1. Put a drop of methylene blue on a glass slide

  2. Gently rub the inside of your cheek with a cotton bud

  3. Wipe the end of the cotton bud in the drop of methylene blue on the glass slide

  4. Place the cotton bud in a beaker of disinfectant

  5. Use a mounted needle to gently lower a coverslip onto the glass slide

  6. Use a light microscope to examine the slide
• Examination of onion cells using a light microscope

  1. Using forceps, peel a thin layer of epidermis from the inside of a freshly cut piece of onion

  2. Lay the epidermis onto a glass slide

  3. Add a drop of iodine solution to the onion epidermis on the glass slide

  4. Use a mounted needle to gently lower a coverslip onto the glass slide

  5. Use a light microscope to examine the slide
• Magnification


  Calculated by dividing the length of an object on the picture by its real length
• Light microscopes allow you to see the image because light passes through it
• It is impossible to magnify an image by more than x1000 with a light microscope
• Electron microscope

  • Uses a beam of electrons instead of light
  • Can achieve much larger magnifications, up to x50,000,000
  • The image is displayed on a monitor
  • Can only study dead cells
• Iodine solution

  Makes the nucleus more obvious and stains any starch present
• Methylene blue

  Stains acidic parts of the cell blue and makes the nucleus more obvious
• Magnifying power of microscopes

  • Low power: x10 eyepiece, x4 objective, total x40
  • High power: x10 eyepiece, x20 objective, total x200
• Unicellular organisms

  Simplest forms of living organisms made of only one cell
• Multicellular organisms

  Organisms that consist of many cells
• Human beings are made up of approximately 34 to 37 trillion cells
• Specialised cells

  Cells that differentiate to carry out specific functions more efficiently than non-specialised cells
• Levels of organisation within organisms

  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Organism
• X10

  Magnification
• X20

  Magnification
• X200

  Magnification
• Total magnification

  Multiplication of the power of the eyepiece lens by the power of the objective lens
• The simplest forms of living organisms are made of only one cell. They are called unicellular organisms.
• Organisms that consist of many cells are called multicellular.
• Scientists have recently estimated that human beings are made up of approximately 34 to 37 trillion cells.
• Not all cells are the same. Cells specialise to carry out specific functions more efficiently than non-specialised cells, e.g. red blood cells carry oxygen.
• Levels of organisation within organisms

  • Specialised cells
  • Tissues
  • Organ
  • Organ System
• Specialised cells

  Cells differentiate to cells with a specific function, e.g. muscle cells
• Tissues

  Groups of similar cells with a similar function, e.g. muscle cells contract and therefore shorten
• Organ

  Several tissues performing specific functions, e.g. the heart pumps blood
• Organ System

  A number of organs working together to carry out specific functions, e.g. the circulatory system carries substances around the body
• Diffusion


  Molecules diffuse from an area of high concentration to an area of low concentration. This process does not require energy.
• Factors affecting rate of diffusion

  • Concentration (the greater the difference in concentration, the faster the rate)
  • Temperature (as temperature increases, the rate increases)
  • Pressure (high pressure causes molecules to move from high to low pressure)
• Molecules are constantly moving and colliding against each other in liquids and gases, which we see in the process of diffusion.