Chapter 3

• What are the two methods of studying cells?

  Microscopes

  Cell Fractionation
• What are the two types of microscopes?

  Light and Electron
• What does a light microscope do?


  Uses light, produces a 2D colour image, and it smaller and easier to maintain.
• What is resolution?

  the minimum distance apart that two objects can be in order for them to appear as separate items
• What is magnification?


  How many times bigger the image is compared to the object
• How does an electron microscope have a greater resolution than a light microscope?

  Uses beams of electron which have a shorter wavelength and therefore a higher resolution
• What are the two types of electron microscopes?

  Transmission and Scanning
• Describe how to carry out cell fractionation:

  1. Place cells in a buffered, isotonic and ice cold solution
  2. Homogenise the solution
  3. Filter to remove whole cells and cell debris
  4. Spin in a centrifuge at a relatively low speed
  5. Remove the supernatant into another test tube and spin at a higher speed to separate smaller organelles
  6. Remove pellet once reached desired organelle
• Why must the solution be buffered?

  Stops bonds breaking due to pH
• Why must the solution be isotonic?

  stops osmosis
• Why must the solution be ice cold?

  slows enzyme controlled reactions so organelles are not hydrolysed
• How does a TEM work?

  Electron beams are focused using electromagnets

  0.17nm resolution

  x50 million magnification

  Forms a photomicrograph

  2D image

  Grey Scale
• What is the preparation for a TEM microscope?

  thin cross sections

  fixed and dehydrated

  osmium used

  Skilful and complex process
• How does a SEM work?

  electromagnetic

  1nm resolution

  x1 million magnification

  3D image

  grey-scale
• What is needed for SEM preparation?

  Sample is fixed

  Dehydrated

  Mounted onto a stub

  Difficult proccess
• Disadvantages of electron microscopes?

  only dead specimens

  need experience

  expensive to run

  complex staining techniques
• Prokaryotic Cells

  Much smaller than eukaryotic

  No membrane bound organelles
• Bacterial Cell:

  Plasmid - circular DNA

  Genetic Material - Large DNA circle folded

  Cell surface membrane

  Ribosomes - smaller, 70s

  Cell Wall - thick murein wall

  Cytoplasm - jelly like and contains enzymes where reactions take place

  Capsule: a mucilaginous layer of slime
• Virus Cell:

  Attachment proteins

  Genetic material

  Reverse Transcriptase

  Matrix

  Capsid

  Lipid envelope
• Viruses are...?

  acellular

  non-living
• Stages of mitosis?

  IPMATC:

  Prophase

  Metaphase

  Anaphase

  Telophase

  Cytokinesis
• What happens in prophase?

  Chromosomes condense and become visible, the nuclear membrane breaks down, and the spindle fibres form.
• What happens in metaphase?

  Chromosomes align in the middle of the cell.
• What happens in anaphase?

  Chromosomes separate and move to opposite poles of the cell.
• What happens in telophase?

  Chromosomes reach poles and become indistinct and nuclear envelopes reform.
• What happens in cytokinesis?

  Cell division
• How do you measure cells using a eyepiece graticule and a stage micrometre?

  Calibrate

  Align stage micrometre and eyepiece graticule

  Know that 1 occular unit = 25um
• Eukaryotic Cell Structure:

  cell membrane

  nuclear pore

  nucleolus

  nuclear envelope

  smooth ER

  rough ER

  mitochondria

  Golgi apparatus

  ribosomes

  centriole

  chloroplast
• Cell membrane function?

  controls entry and exit of substances in and out of the cell.
• Nuclear pore function?

  allows entrance and exit
• Nucleolus function?

  makes ribosomal RNA
• nuclear envelope function?


  Separates nucleus from cytoplasm.
• Smooth endoplasmic reticulum function?

  synthesises, stores and transports lipids and carbohydrates
• Rough endoplasmic reticulum function?

  Protein synthesis and modification.
• Mitochondria function?

  aerobic respiration for energy
• Golgi apparatus function?

  forms lysosomes, secrete carbs, enzymes and modifies molecules.
• Ribosome function?

  Protein synthesis
• Centriole function?

  Spindle fibres
• Chloroplast function?

  Photosynthesis
• Cell speciation and organisation?

  Organelles, Cells, Tissues, Organs, Organ Systems, Organisms