8.2 cells

• Cells are so small that about 100 animal cells would fit across the width of this full stop
• There are different types of cells in your blood
• Most household dust is actually dead cells. These come from anything living in your house
• All living organisms are made of cells
• Cells are the building blocks of life
• Organisms such as bacteria can be formed from a single cell
• Millions of cells can join together to form a person, like you
• Cell


  The smallest unit found in an organism
• Robert Hooke


  • A scientist who first saw plant cells when looking at a thin slice of cork through a microscope
  • He called the structures he saw 'cells'
• Observation


  Looking carefully and in detail at an object
• Microscope


  • Magnifies the image using lenses
  • Object needs to be very thin so light can travel through it
  • Coloured dye may be needed to make the object easier to see
• Eyepiece


  Part of the microscope you look through
• Magnification


  The eyepiece lens and objective lens together magnify the object
• If the eyepiece lens has x10 magnification and the objective lens has x20 magnification, the total magnification is 200 times
• Steps to observe an object using a microscope


  1. Move stage to lowest position

  2. Place object on stage

  3. Select lowest magnification objective lens

  4. Look through eyepiece and turn coarse-focus knob until object is seen

  5. Turn fine-focus knob until object is in focus

  6. Repeat using higher magnification objective lens
• When recording microscope observations, you should note the magnification used
• Key components found in animal cells


  • Nucleus
  • Cell membrane
  • Cytoplasm
  • Mitochondria
• Nucleus


  Controls the cell and contains genetic material
• Additional components found in plant cells


  • Cell wall
  • Vacuole
  • Chloroplasts
• Cell wall


  Strengthens the cell and provides support, made of cellulose
• Vacuole


  Contains a watery liquid called cell sap, keeps the cell firm
• Chloroplasts


  Where photosynthesis happens, contain chlorophyll
• The prefix 'chloro-' means 'green'
• Prefixes and their meanings


  • Bio- = life
  • Photo- = light
  • Micro- = small
• Specialised cells have different features that are suited to their function
• Specialised cell


  A cell that has changed to carry out a particular job
• Nerve cell


  • Long and thin with connections at each end to transmit messages
  • Function is to carry electrical impulses around the body
• Red blood cell


  • Disk-like shape to increase surface area for carrying oxygen
  • Contains haemoglobin but no nucleus
• Sperm cell


  • Streamlined head and long tail to allow movement through liquid
  • Contains many mitochondria to provide energy for swimming
• Leaf cell


  • Long and thin, packed with chloroplasts to absorb sunlight for photosynthesis
  • Has a cell wall and chloroplasts, unlike animal cells
• Root hair cell


  • Long and thin to increase surface area for absorbing water and minerals from the soil
• Sperm cell


  • Contains lots of mitochondria to transfer energy
  • Tail allows the sperm cell to swim
  • Head of the sperm burrows into the egg cell
• Not all plant cells are the same. Cells in different parts of a plant are specialised to perform their job
• Leaf cell


  Contains cytoplasm that stores chloroplasts and a large vacuole
• Leaf cell from the top of a leaf


  • Its scientific name is a palisade cell
  • Carries out photosynthesis
  • Long and thin shape
  • Packed with chloroplasts
  • Large surface area for absorbing energy from the Sun
• Root hair cell


  • Absorbs water and nutrients from soil
  • Creates a large surface area for absorbing water and nutrients
  • No chloroplasts as there is no light underground, so no photosynthesis
• Substances move from an area where they are in a high concentration to an area where they are in a low concentration. This process is called diffusion
• Uni-cellular organism


  Made up of just one cell, not a plant or animal
• Uni-cellular organisms are adapted to carry out functions that in multi-cellular organisms are done by different types of cell
• Amoeba


  • Has no fixed shape
  • Found in fresh water, salt water, wet soil, and inside animals
  • Consists of a cell membrane filled with cytoplasm, with a nucleus that controls growth and reproduction
  • Moves by changing the shape of its body