cell structure

• there are 3 types of microscope:

  • light/optical microscope
  • electron microscope
  • laser scanning confocal microscope (LSCM)
• differential staining:

  • different parts of a specimen can be made to stand out by covering them in different stains
• iodine:

  • stain cellulose and starch in plant cells
• eosin:

  • stains the cytoplasm
• sudan red stains lipids
• acetic orecin stains DNA dark red
• leishman's stain : differentiate between blood cells
• methylene blue: allows parts of an animal cell to stand out
• radiation of light microscope: light
• radiation of electron microscope: electrons
• light microscopes focused by: lenses
• electron microscope focused by : electromagnets
• max magnification for light: 1500-2000x
• max magnification for SEM : 250,000
• max magnification for TEM: 2,000,000
• specimens for light : living/dead
• specimens for electron: dead
• slide preparation for light microscope:

  • differential staining, thinly sliced
• slide preparation for electron:

  • SEM- covered in a layer of heavy metal eg gold
• max resolution for light: 200nm
• max resolution for electron:

  • TEM = 0.5nm
  • SEM= 3-10nm
• resolution: is the ability to distinguish between 2 separate point
• magnification = image/actual
• SER: no ribosomes, synthesis of lipids and steroids eg cholestrol and transport
• RER: membrane covered with ribosomes, responsible for protein synthesis and transport
• ribosomes:

  • composed of RNA and proteins
  • protein synthesis
• Golgi apparatus: stack of flattened sacs produced by SER , end form Golgi vesicles which transport glycoproteins and carbohydrates to other parts of the cell

  function: modify proteins, joining carbohydrates and proteins to form glycoproteins and the secretion of carbohydrates
• lysosome: spherical sacs containing hydrolytic enzymes

  function: responsible for digestion for old organelles, whole cells and bacteria during infection

  • sperm cells contain a special type to allow the breakdown of acrosome surrounding ovum
• mitochondria: surrounded by a double membrane the inner one is highly folded to form cristae which project into the inner liquid matrix

  function: Krebs cycle and oxidative phosphorylation stages of aerobic respiration, producing ATP molecules
• plasma membrane: composed of phospholipids and various proteins

  functions: it is partially permeable membrane and controls the movement of solutes between the cell and its environment
• cilia/flagella: move in a wave like manner moving the cell if independent or moving the cell next to it if fixed
• chloroplast: site of photosynthesis
• nucleus: contains genetic material and controls cell activities, controls cell division, controls cell growth and development

  • surrounded by the nuclear envelope, a double membrane
• centrioles: form spindle fibres during cell division
• cytoskeleton: is an internal network of fibres and proteins structures which maintain the cells shape and structure
• fibres :

  1. microfilaments
  2. microtubules
  3. intermediates filaments
• microfilament: such as actin fibres move against each other and allow cell movement

  • phagocytosis in WBC
  • chromosomes in cell division
• microtubules: made of the protein tublin, they give the cell the structure and track for the movement of organelles

  • eg the movement of vesicles
• flagella: whip like tail enables cell to move (eg: sperm)
• cilia: shorter 'brush' like attachment waft surrounding liquid/objects