B1

• Eukaryote cells have a nucleus (e.g. animal and plant cells)
• Prokaryote cells don't have a nucleus (e.g. bacteria cells)
• What is microscopy?


  Using microscopes to magnify samples that cannot be seen with the naked eye.
• Ribosomes are found in the cytoplasm of a cell and are where protein synthesis occurs.
• Organisms can either be prokaryote or eukaryote cells.
• A prokaryote is a single-celled organism.
• Sub-cellular: Smaller than a cell.
• Mitochondria are found in the cytoplasm of a cell and are where respiration occurs.
• Eukaryotes are any organisms or cells that have their genetic information stored as DNA in a sub-cellular structure called a nucleus.
• Prokaryotes are any organisms or cells that have their genetic information found in a single DNA loop in a sub-cellular structure called plasmids.
• All living organisms are made from cells.
• How can you categorise the two diffrerent types of cells?

  Based on where the genetic material is found.
• The nucleus contains genetic material and controls the activity of the cell.
• Cytoplasm is where most of the chemical reactions happen. It contains enzymes which control these chemical reactions.
• Cell wall is made of cellulose and keeps the shape of the cell. (Plant cell)
• Cell membrane controls the movements of what goes in and out of the cell.
• Permanent vacuole stores the cell sap. (Plant cell)
• Chloroplast contains chlorophyll and is where photosynthesis occurs. (Plant cell)
• Plasmid is where the genetic information is found. (Bacteria cell)
• Flagella allow the bacteria to move, however, not every bacteria cell has this.
• • One centimetre = 0.01 m = 1 x 10−2m 
  • One millimetre = 0.001 m = 1 x 10−3m
  • One micrometre = 0.000001 m = 1 x 10−6m
  • One nanometre = 0.000000001 m 1 x 10−9m
• Cells are too small to be viewed with the naked eye, so we use microscopes to look at cells in detail.
• Light microscopes use light and lenses to form an image of a specimen.
• Electron microscopes use electrons to form an image or a specimen.
• Electron microscopes have a much higher magnification and resolution than light microscopes.
• Magnification = eye piece x objective lens
• Size of object = size of image / magnification
• Magnification = image size / real size
• Differentiation is the process by which a cell changes to become specialised for its job.
• In animal cells:

  • Most differentiate at an early stage
  • Cell division only happens for repair and replacement.
• In plant cells:

  • Remain able to differentiate throughout life.
• Sperm cells are specialised for reproduction.
• Nerve cells are specialised for rapid signalling.
• Root hair cells are specialised for absorbing water and minerals.
• Phloem and xylem cells are specialised for transporting substances.
• Undifferentiated cells are called stem cells.
• Magnification is how much bigger the microscope can make an object appear.
• Resolution is the detail that can be seen from the microscope.
• Body cells in multicellular organisms divide to produce new cells as part of a series of stages called the cell cycle.
• When a cell divides, it is known as mitosis.