Topic 1 - Cell Biology

• Cells


  The basic unit of all human life
• Eukaryotic cells

  • Plants
  • Animals
• Eukaryotic cells always have:

  • Cell membrane
  • Cytoplasm
  • Nucleus
• Nucleus


  Contains the DNA for the cell.
• Prokaryotic cells have

  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Single large loop of DNA
  • Plasmids (sometimes)
  • Flagella (sometimes)
• Prokaryotic cells store their DNA in

  • Single large loop of DNA
  • Plasmids
• Eukaryotic cells store their DNA in

  Nucleus
• Cytoplasm


  Liquid substance where chemical reactions occur
• Cell membrane


  Controls what enters and leaves the cell
• Mitochondria

  Where aerobic respiration occurs - which provides energy for the cell
• Ribosomes

  Where protein synthesis occurs
• Most animal cells have

  • Nucleus
  • cytoplasm
  • cell membrane
  • mitochondria
  • ribosomes
• Plant cells have (animal cells don't)

  • Chloroplast
  • Permanent vacuole
  • Cell wall
• Chloroplasts

  • Where photosynthesis takes place which provides food for the plant.
  • Contains chlorophyll which attracts sunlight and makes the cell green
• Permanent vacuole

  • Contains cell sap.
  • Improves cells rigidity.
• Cell wall

  • Made from cellulose (in eukaryotic cell)
  • Made from peptidoglycan (in prokaryotic cells)
  • Provides strength to the cell
• Plasmids

  Small rings of DNA
• Single large loop of DNA

  where DNA is stored in prokaryotic cells since they have no nucleus.
• Orders of magnitude

  1. Kilometre (km)
  2. Metre (m)
  3. Centimetre (cm)
  4. Millimetre (mm)
  5. Micrometre (μm)
  6. Nanometre (nm)
• Specialised cells


  Cells which have a specific shape or structure as well as specific number of organelles in order to do a specific role.
• Differentiation


  The process by which cells change to become specialised.
• Specialised cells

  • Sperm cell
  • Red blood cell
  • Muscle cell
  • Nerve cell
  • Root hair cell
  • Xylem cell
• Sperm cell


  Its role is to fertilize an egg. It's adapted to do this by:

  • having a flagellum (tail) to swim to the egg and fertilize it.
  • Having lots of mitochondria to release lots of energy so the cell can swim
  • Having digestive enzymes on the top of its head to break down the outer layers of membrane on the egg.
• Red blood cell


  Its role is to transport oxygen around the body. Its adapted to do this by:

  • Having no nucleus so more room to carry oxygen
  • Containing a red pigment called haemoglobin which binds to oxygen
  • Having a flat bi-concave shape to increase surface area to volume ratio.
• Muscle cell


  Its role is to contract and relax for movement. Its adapted to do this by:

  • Containing protein fibres which can contract to make cells shorter
  • Contains lots of mitochondria to release energy from respiration allowing muscles to contract.
• Nerve cell


  Its role is to carry electrical impulses around the body. Its adapted to do this by:

  • Having branched endings called dendrites to make connections.
  • Axon is long enabling the impulses to be carried long distances.
  • Nerve endings have many mitochondria which supply energy.
• Root hair cell


  Its role is to absorb mineral ions and water. It's adapted to do this by:

  • Have a large surface area meaning more water can come in.
  • Large permanent vacuole affects the speed of water coming in.
  • Lots of mitochondria provides energy for active transport.
• Xylem cells


  Its role is to transport water and mineral ions from the roots. Its adapted to do this by:

  • They are hollow which means the water and mineral ions can move through.
  • Lignin is deposited in spirals which helps to withstand pressure.
• Stem cells


  Stem cells can divide by mitosis to form more cells in order to differentiate into specialised cells.
• Embryonic stem cells


  cells in an embryo which can differentiate to form specialised cells. For example nerve cell or red blood cell
• Adult stem cell


  Stem cells in an adult body which can differentiate into specific specialised cells. For example bone marrow can differentiate into platelets or red or white blood cells
• How a baby is made

  1. Sperm fertilises an egg
  2. Form a single cell called a zygote
  3. This divides by mitosis to form a ball of cells called an embryo
  4. The embryo contains embryonic stem cells
  5. These cells differentiate into any type of cell
• Meristems


  Where plant stem cells are found. Areas of the plant which are continually growing. Found in the tips of shoots and roots of the plant.
• Light microscope

  • Uses light to form images
  • Living samples can be viewed
  • Relatively cheap
  • Low magnification
  • Low resolution
• Electron microscope

  • Uses a beam of electrons to form images
  • Samples cannot be living
  • Expensive
  • High magnification
  • High resolution
  • Used to see sub cellular structures.
• Magnification calculation

  Magnification = Image size ÷ Actual size
• What is the pathway of light through a microscope?

  Light source ➔ stage ➔ microscope slide ➔ object ➔ objective lens ➔ body tube ➔ eyepiece lens ➔ eye
• Parts of a microscope

  • Eyepiece lens
  • Objective lens
  • Stage
  • Microscope slide
  • Base
  • Light
• Magnification


  How many times larger the image is than the object.
• Resolution


  A measure of how detailed the image is. The higher resolution the more detail.