Module 1

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  • Created by: Sumera
  • Created on: 18-09-13 17:44

Microscopy

Magnification:

how many times LARGER the IMAGE is THAN THE ACTUAL IMAGE

Resolution:

the ability to see TWO DISTINCT POINTS SEPERATELY even when they're CLOSE TOGETHER

 

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Light Microscope

magnification: x1500

resolution: 200 nm

  • GLASS LENSES are used to focus and produce the image
  • STAINING the specimen is required (methylene, blue iodine)
  • dead and LIVING SPECIMEN can be examined
  • CONDENSER LENS focuses light onto the specimen
  • OBJECTIVE LENS magnifies and focuses the image
  • EYEPIECE magnifies the image as well

advantages: cheap, prep is quick and simple, living things can be examined

limitations: low res, low magnification, 2D image

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Electronic Microscopes

  • ELECTRONIC BEAM
    • wavelength SMALLER than light
      • so a HIGHER RESolution image
      • image is PROJECTED onto a SCREEN/photographic plate
      • BLACK AND WHITE image
  • ELECTROMAGNETS are used for focusing and magnifying
  • electrons are DEFLECTED by AIR particles
    • so sample needs to be DEAD
    • area needs to be VACUUMED

SEM: magnification: x100 000
  resolution: 0.2 nm
electrons DO NOT PASS through, electrons BOUNCE OFF the sample, elctrons are collected to produce a 3D image of the SURFACE

TEM: magnification: x500 000
  resolution: 0.2 nm
electrons
PASS THROUGH, pass through with difficulty in DENSER areas (causing CONTRAST), and a 2D image is produced 

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Calculating Magnification

CM -----------> MM
       X10  

MM -----------> IU 
      X1000 

IU ------------> NM
      X1000 


magnification = diagram size
                                                     

                                      real size    

 both SIZES have to be in the SAME UNITS  

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Movement and Stability in Cells

  • CYTOSKELETETONNETWORK of FIBRES (made of PROTEIN) to provide STABILITY, STRUCTURE and SHAPE
    • FINE ACTIN FILAMENTS (are like fibres in muscles cells)  move against each other to CHANGE the cell's shape
    • MICROTUBLES used to MOVE a microorganism or to WAFT a liquid PAST the cell
  • Undulipodia (flagella)
    • HAIR like exntensions- STICK out from the surface of the cell
    • made up of MICROTUBLES
    • help with MOVEMENT
  • CILLIA
    • HAIR like extensions- STICK out from the surface of the cell
    • BEAT to POWER cell MOVEMENT/wafting
  • PLANT CELL WALLS
    • made of CELLULOSE- SIEVE LIKE network of strands
      • makes the wall STRONG- held rigid by the PRESSURE of the fluid inside
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Membrane Bound Organelles

  • THE NUCLEUS: contains GENETIC MATERIAL
    • CHROMATIN contains DNA and the INSTRUCTIONS for making protein
    • NUCLEOLUS makes RIBOSOMES
  • ER: series of INTERCONNECTED membranes
    • RER: TRANSPORTS proteins (that were attached to the ribosomes)
    • SER: involved in making LIPIDS
  • GOLGI APPARATUS: STACK of sacks
    • protein: RECIEVES, MODIFIES (adding carbohydrate) & REPACKAGES (into vesicles)
  • MITOCHONDRIA: TWO membranes, inner membrane is FOLDED to form CRISTA
    • produces adenosine triphosphate (ATP) during RESPIRATION, provides ENERGY
  • CHLOROPLAST: TWO membranes, inner membrane filled with flattened sacs THYLAKOIDS
    • site of PHOTOSYNTHESIS 
  • LYSOSOMES: spherical
    • contains ENZYMES to BREAK down bacteria, water, and malfunctioning organelles
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Organelles without membranes

  • RIBOSOMES: tiny organelles
    • ASSEMBLE protein by TRANSLATING the mRNA code


  •  CENTRIOLES: small tubes of protein fibres, MICROTUBULES. TWO of them next to the nucleus in animal cells
    • cell DIVISON
    • form FIBRES (spindle) to MOVE the CHROMOSOMES during nuclear division 
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Division of Labour (Protein Synthesis)

Hormones are chemical MESSENGER molecules that help COORDINATE activites

  • The INSTRUCTIONS to make the hormone are in the DNA
    •  (specific instructions are known as the gene for that hormone)
      • (a gene is on a chromosome)
  • NUCLEUS COPIES the DNA onto a molecule called mRN
  • mRNA leaves through nucleur pore and ATTACHES itself to a RIBOSOME (or the RER depending on where the ribosomes are)
  • the ribosome READS the instructions and uses the codes to ASSEMBLE the hormone (protein)
  • the protein is TRANSPORTED via a VESICLE to the GOLGI APPARATUS
  • the golgi apparatus MODIFIES (by adding carbohydrate) the protein
  • protein is REPACKAGED into a vesicle and moved to the cell SURFACE to be SECRETED
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Prokaryotic Cells (bacteria)

  • NO NUCLUES
  • contain only ONE membrane
    • NO membrane bound organelles
  • surrounded by a CELL WALL- made up of PETIDOGLYCAN
    • sometime there is a slippery PROTECTIVE layer called the CAPSULE
  • ribosomes < eukaryotic ribosomes
  • single LOOP of DNA
    • not surrounded by a membrane
    • the area where the DNA is found is called the NUCLEOID
    • many contain SMALL LOOPS of DNA called PLASMIDS
  • ATP takes place in MESOSOMES (similar to mitochondria)
  • have hair like structures called PILLI (singular pillus)
    • sometimes have FLAGELLA but with a DIFFERENT internal STRUCTURE than the eukaryotic cells
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