2.2 Basic Components of Living Systems (Spec)

Question 1

Light microscopy

Answer 1

Easily available
Relatively cheap
Used out in field
Beam of photons illuminate, pass through to form image
Living and dead specimens
0.2 micrometer res, 1500x mag

Question 2

Differential staining

Answer 2

Distinguish 2 organism types
Distinguish different organelles in cell (tissue sample)
Otherwise difficult to distinguish
Increases contrast

Question 3

Magnification

Answer 3

How many times larger the image size produced is than the actual size of the specimen
Magnification = Image/Actual

Question 4

Dry mount

Answer 4

Solid specimens
Placed on slide, coverslip flat
Hair, pollen, dust - whole
Muscle tissue/plants - sectioned

Question 5

Wet mount

Answer 5

Aquatic/living specimen
Specimen suspended in liquid (water/immersion oil)
Coverslip at angle

Question 6

Squash slide

Answer 6

Soft specimen
Wet mount
Gently press coverslip
Sample between 2 slides - prevent coverslip damage
Root tip squashes - cell division

Question 7

Smear slide

Answer 7

Liquid specimen
Edge of slide smear sample on another slide
Thin even coating

Question 8

Staining

Answer 8

Increase contrast between different cell components
Different degrees of stain adhesion
Contrast - visibility - identification

Question 9

Scientific drawing criteria

Answer 9

Title
Magnification
White, unlined paper
Sharp pencil
Smooth, continuous lines
Label lines parallel to top of page - ruler
Proportion correct
No arrowheads or crossing label lines

Question 10

Positive staining

Answer 10

Methylene blue/Crystal violet
Positive charge attracted to negative charge in cytoplasm
Staining of cell components

Question 11

Negative staining

Answer 11

Nigrosin/Congo red
Negative charge repelled by negative charge of cytoplasm
Unstained cell, contrast with stained background

Question 12

Resolution

Answer 12

Shortest distance between two objects, still seen as separate objects

Question 13

Gram stain technique

Answer 13

Crystal violet,
Gram's iodine,
Alcohol (gram-negative decolourisation)
Safranin (gram-negative colourisation)
gram-negative - pink (safranin)
gram-positive - purple (crystal violet)

Question 14

Acid-fast technique

Answer 14

Lipid solvent & carbolfuchsin dye
Dilute acid-alcohol solution
Methylene blue
Mycobacterium - red (carbolfuchsin)
Other bacteria - blue (methylene blue)

Question 15

Laser scanning confocal microscopy properties/workings

Answer 15

Focused light spot across specimen - point illumination
Fluorescence from components labelled w/ dye filtered through pinhole aperture
Light from and very close to focal plane
- detected
Light from other parts of specimen - not detected through pinhole aperture
Blurring, reduce resolution
Laser - high intensity, high illumination
Non-invasive

Question 16

Laser confocal microscopy uses

Answer 16

Eye disease diagnosis
Endoscopy
Drug development - molecule distribution in cells
Virtual biopsy - suspected skin cancer

Question 17

Electron microscopy

Answer 17

Electron wavelength <1nm
Magnification 500,000x - clear resolution
Ultrastructure visible - dead specimens
Expensive, controlled environment
Specimen damage - electron beam
- slide preparation (artefacts)

Question 18

TEM

Answer 18

Electron beam transmitted through specimen
Focused w/ electromagnets -> image
O.5nm resolution

Question 19

SEM

Answer 19

Electron beam transmitted across specimen surface

Reflected electrons collected -> 3D image