microscopes Flashcards
1
Q
describe compound light microscope
A
- objective lens : near specimen
- eyepiece lens : specimen is viewed through
- illumination by light underneath the sample
- eyepiece magnifies, objective magnifies again
- reduces chromatic aberration
2
Q
dry mount prep
A
- section solid specimen (cut/whole but thin)
- placed on centre of slide
- cover slip over
- e.g hair , dust / sectioned muscle
3
Q
wet mount prep
A
- specimen suspended in a liquid(water)
- cover slip over on an angle
- ## no air bubbles
4
Q
smear slides
A
- edge of slide smears the sample
- thin even coating
- E.G blood
- views cells
5
Q
use of staining
A
- increase contrast
- diff components of cells take up stain to diff degrees
- components more visible
- sample on slide is air dried
- heat fixed (passed through a flame)
- specimen adheres to slide
- will take up stains
- E.G crystal violet/methylene blue(DNA)
- Congo red = negative stain
- eosin (cytoplasm)
- in e- microscope stain = solution of heavy metals (lead) bc they scatter e- creating contrast.
6
Q
differential staining
A
- distinguishes between 2 type of organisms
- differentiate between diff organelles within a tissue sample
7
Q
magnification equation
A
magnification = image size (with ruler)/ actual size
8
Q
nm = micrometre micrometre = mm mm = m
A
- 1000nm = 1 micro
- 1000micro = 1mm
- 1000mm = 1m
9
Q
electron microscopes
A
- beam of e-
- shows cell ultrastructure
- over x500000 magnification
- expensive
- used inside controlled env
- specimen can be damaged by e- beam
10
Q
transmission e- microscope
A
- beam of e- transmitted through a specimen
- produces an image
11
Q
scanning e- microscope
A
- beam of e- across a surface
- collects reflected e-
- 3D image of surface
12
Q
light v electron microscope
- compare magnification/resolution
A
L : inexpensive E : expensive L : small + portable E : large + installed L: no vacuum E : requires vacuum L : living/dead specimen E : dead specimen
L : - R = 0.2micrometres - M = x1500 TEM: - R = 0.0002micrometres - M = more than x1000000 SEM: - R = 0.002 micrometres - M = less than 500000
13
Q
prokaryotes
A
- single celled
- simple structure
- cytoplasm : no membrane bound organelles
14
Q
eukaryotes
A
- multicellular
- complicated internal structure
- membrane bound nucleus
- cytoplasm : membrane bound components
15
Q
nucleus
A
- contain genetic info
- DNA directs protein synthesis
- control metabolic activities of the cell
- DNA contained in double membrane = nuclear envelope
- NE has nuclear pores (mol move in/out of nucleus)
- DNA combines with histones to form chromatin
- chromatin coils/condenses = chromosomes
16
Q
nucleolus
A
- in nucleus
- produces ribosomes
- composed of proteins + RNA
- RNA produces rRNA
- rRNA combines with proteins to form ribosomes
17
Q
mitochondria
A
- cellular respiration
- double membrane
- inner membrane is folded = cristae
- fluid interior = matrix
- membrane of cristae has enzyme used in aerobic resp
- ribosomes : produce own proteins
- reproduce themselves
18
Q
vesicles
A
- membranous sacs
- storage/transport roles
- single membrane with fluid inside
19
Q
lysosomes
A
- specialised forms of vesicles
- hydrolytic enzymes
- break down waste material in cells
- immune system : break down pathogens
- role in cell death
20
Q
cytoskeleton
A
- in cytoplasm
- network of fibres
- shape
- stability
- organelles held in place
- control cell movement
21
Q
components of cytoskeleton
A
microfilaments : - contractile fibres formed from actin(protein) - cell movement - cell contraction during cytokinesis - microtubules : - shape of the cell - tracks for cell movement - make spindle fibres
intermediate fibres:
- mechanical strength
- maintain their integrity
22
Q
flagella/cilia
A
- extensions
- flagella enable cells movement
- cilia = mobile or stationary
- cilia : surface of sensory organs (nose)
- cilia : move in rhythmic manner to move mucus
23
Q
endoplasmic reticulum
A
- network of membranes
- encloses cisternae (flattened sacs)
- smooth ER : lipid/carb synthesis + storage
- rough ER : ribosomes bound to surface + synthesis + transport of proteins
24
Q
ribosomes
A
- no membrane
- made of RNA mol (nucleolus)
- site of protein synthesis
25
golgi
- formed of cisternae
- no ribosomes
- modifies proteins
- packaging proteins into vesicles to leave cell
- or into lysosomes to stay in cell
26
protein productions - interrelationship of organelles
- proteins synthesised on ribosomes
- bound to RER
- pass into cisternae
- packaged into transport vesicles
- vesicles move to golgi via cytoskeleton
- vesicles fuse with cis face golgi
- proteins enter
- proteins structurally modified
- leave golgi in vesicles from trans face
- secretory vesicles carry proteins
- move towards + fuse with CSM
- releasing content by exocytosis
- some vesicles form lysosomes
- contain enzymes used in cells
27
cell wall
- cellulose
- give it shape
- rigid
- defence mechanism protecting inside from pathogens
28
vacuoles
- membrane lined sacs
- contain cell sap
- maintain turgor
- membrane = tonoplast
- selectively perm
29
prokaryotic DNA
- one mol of DNA (chromosomes)
- supercoiled
- more compact
- genes grouped in operons
- number of genes switched on/off
30
prokaryotic ribosomes
- smaller than euk
| - protein synthesis
31
prokaryotic cell wall
- made from murein
| - complex polymer from amino acids + sugar
32
prokaryotic flagella
- thinner than euk
- energy supplied by chemiosmosis
- rotated by molecular motor
33
euk/prokaryotes ultracellular structure comparison
nucleus : Euk
DNA : Pro(circular) + Euk(linear)
cell wall : Pro(murein) + Euk(cellulose in plants/chitin in fungi)
ribosomes : Pro(smaller 70S) + Euk(larger 80S)
reproduction : Pro(binary fission) + Euk(a/sexual)
cell membrane : Euk + Pro
organelles : Pro(non-membrane bound) + Euk(both membrane + non-membrane bound
