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MICROSCOPES (&ETC.) (/82)

Isra Khan Biology AS - Level Englisch 45 Karten

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  1. 1what is an electron micrograph? [1]photograph of an image seen using an electron microscope
  2. 2MAGNIFICATION: definition [2]-no. of times larger an image appears compared to the original size of the object.
    -Produce linear magnification (x10 = x10 in width and length)
  3. 3what is a photomicrograph? [1]photograph of an image seen using an optical microscope
  4. 4triangle for calculating mag, actual image, & image ? [1]M = I / A
  5. 5RESOLUTION: definition [2]-(with relation to optical instruments) the clarity of an image - higher resolution, clearer image
    OR
    -the distance between each distinguishable point in the image
  6. 6what are organelles? [1]small structures within cells. each has a specific function.
  7. 7where are optical microscopes used? [4]-schools
    -colleges
    -hospitals
    -research laboratories
  8. 8good qualities of optical microscopes? [4]-relatively cheap
    -easy to use
    -portable and able to be used in field & laboratories
    -can be used to study whole living specimens
  9. 9what do optical microscopes rely on? include wavelengths & describe this in brief detail. [3]-lenses to focus a beam of light.
    -use visible light (part of emag spectrum). w/l 400-700nm.
    -structures closer than 200nm (0.2Mm appear as one object)
  10. 10OPTICAL microscopes - a) mag b) what this allows us to see c) comment on resolution [3]a) x1500, some x200
    b) see clearly some larger structures inside cells
    c) limited. cannot see higher than x1500/x2000 while giving clear image
  11. 11an example of an organism which cannot be seen with a light microscope? why? [1]ribosomes. they are 20nm so too small.
  12. 12describe (IN v DETAIL) how to use a light microscope [8]1 - specimen on slide on stage & clipped into place.
    2 - rotate nosepiece & place on lowest power/smallest objective lense over specimen (x4+x10 total x40).
    3 - adjust coarse focus knob while looking into eyepiece until clear focused image
    4 - adjust iris diaphragm for optimum light while viewing
    5 - object directly over hole in stage. rotate nosepiece & bring x10 objective (med) over spec. look down ocular tube & fine focus knob to focus imge.
    6 - repeat step 4&5 for x40 objective lense.
    EXAMPLE STRUCTURE - AWARD 6 MARKS IF INFO ALL CORRECT. EXTRA 2 MARKS FOR USING ALL TERMS
  13. 13where do modern digital microscopes display images? [1]on a computer screen
  14. 14what are Laser Scanning Microscopes (LSMs) also called? [1]Confocal Microscopes
  15. 15How do LSMs work? [1]use laser light to scan object pxp & assemble (via comp) pixel info -> 1 image. displayed on comp screen.
  16. 16what are LSM images like? [1]high resolution & high contrast
  17. 17What do LSMs have and what can they be used for? [2]-depth selectivity.
    -focus on diff structures at diff depths in specimen. can clearly observe /whole living specimens/ & cells
  18. 18where are LSMs used w/ an example? [3]-medical profession. swift diagnosis & earlier more effective treatment
    -e.g. observing fungal filaments in cornea of the eye of patient w fungal corneal infection (or another right example)
    -many branches of biological research
  19. 19ELECTRON MICROSCOPES - what do they use to function [1]-beam of fast-travelling electrong w/ w/l of about 0.004nm.
  20. 20where are these particles released from & describe briefly how they are focused? [2]-electrons fired from cathode
    -focused by magnets not glass lenses onto screen/photographic plate
  21. 21describe the images of EMs. why does the image differ from that of optical microscopes? [2]-clear and highly magified images
    -f-t electrons w/l of about 125,000x central part of visible light spectrum, so better resolution
  22. 22what are the two types of electron microscopes? [1]Transmission election microscopes and Scanning electron microscopes
  23. 23how do TEMs work? (a) describe the process but not the image [2]-specimen must be chemically fixed by being dehydrated and stained
    - beam of electrons passes through specimen which is stained by metal salts. some es pass and focus on screen/photographic plate
  24. 24how do TEMs work (b) describe the image [2]-es form 2D b&w/greyscale image. when photographed called an electron micrograph
    produce mag of up to x2mill. new gen in development for up to x50mill
  25. 25SEMs - when were they developed? [1]1960s
  26. 26SEMs - (a) how do they work (dont describe the image) [2]-specimen has to be placed in vaccuum & often coated w/ fine film of metal
    -electrons dont pass through (whole) specimen. cause 2ndary electrons to 'bounce off' specimen surface & be focused on a screen.
  27. 27SEMs how they work (b) - describe the image [2]-3D b&w/grayscale image w/ mag from x15-x200 000
    - comp software programmes can add false colour
  28. 28'negatives' of both TEMs and SEMs? [3]-large & v expensive. need a great deal of skill & training to use
    -specimens have to be dead (viewed in vaccuum)
    -metallic salt stains used for staining may be potentially hazardous to the user
  29. 29what is a /logarithmic/ scale? [1]one that goes up in steps
  30. 30name 2 cells which can be seen with either the human eye, a light microscope, or an electron microscope [2]an onion epidermis cell and an amoeba
  31. 31name 3 cells which can only be seen using an EM (not a LM or the human eye) [1]3 from:
    -atom
    -lipids
    -ribosome
    -protein
  32. 32these cells can be seen using either an EM or an LM but not the human eye: influenza virus cell / mitochondrion / chloroplast / human cheek cells / human ovum / bacterium which of these three are roughly the same size? [1]mitochondrion, chloroplast & bacterium
  33. 33suggest, with reference to a receptor cell, why the eyes of eagles and hawks have a higher limit of resolution than humans. [2]-(photosensitive cells) cones in eyes. eagles and hawks have more of these (we have 200 000 cones per mm^2 and they have around 1mill)
    INFORMATION IN BRACKETS IS NOT NEEDED TO AWARD THE MARKS. 2 marks for the above point.
  34. 34types of specimens you can view using an optical microscope (with examples)? [4]-living organisms (e.g. Paramecium and Amoeba)
    - smear preparations (e.g. human blood and cheek cells)
    - thin sections of animal, plant and fungal tissue (e.g. bone/muscle, leaf/root, or fungal hyphae) - 1 ex. needed for each 1 mark for 1. extra mark for all 3.
  35. 35non-stained ?...
  36. 36what is differential staining? [1]stains are coloured chemicals that bind to mols (in or on the specimen, making the specimen easy to see). some stains bind to specific cell structures, staining each structure differently so that they can be eaily ideintified in a single preparation (this is differential staining)
  37. 375 examples of stains: [5]-METHYLENE BLUE - all purpose
    -ACETIC ORCEIN - binds to DNA & stains chromosomes dark red
    -EOSIN - stains cytoplasm
    -SUDAN RED - stains lipids
    -IODIDE IN POTASSIUM IODIDE SOLUTION - stains cellulose in plant cell walls yellow, starch granules blue/black (violet under microscope)
  38. 38prepared & permanently fixed slides are made by experts in a laboratory. what are the three key steps of the method? [3]-dehydrating the specimens
    -embedding in wax to prevent distortion during slicing
    -using special instrument to make v thin slices (sections) - stained & mounted in special chem to preserve them
  39. 39what do you times 539mm by to know it's equivalent in Mm? [1]x1000
  40. 40Suggest 3 things to bear in mind when observing structures in a microscope. [3]-cells have a 3D structure and only looking at 2D section
    - depending on where in cell section cut, some structures may be absent from slide section
    - depending on certain structures orientation in cell, appear as different shapes. (mitochondria londitudinal sausage-shaped, transverse round, obliquely (slanting), elliptical)
  41. 41What is an eyepiece graticule? [2]- a measuring device placed in the eyepiece of a microscope. acts as a ruler when viewing an object under the microscope
    - transparent w/ a small ruler etched on it
  42. 42explain how the eyepiece graticule is used? [3]f
  43. 43what is a stage graticule? [1]./
  44. 44explain how to use the stage graticule to calibrate the eyepiece graticule. [9].
  45. 45EX? [2]?

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Beschreibung
MICROSCOPES / SLIDES & PHOTOMICROGRAPHS / MEASURING OBJECTS SEEN W/ A LIGHT MICROSCOPE
Erstellt von
Isra Khan
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