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Biology > Microscopy and cell structure > Flashcards

Microscopy and cell structure Flashcards

1
Q

magnification

A

the number of times and image has been enlarged compared to its actual size

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2
Q

resolution

A

the minimum distance between two objects to be able to distinguish them as two separate objects

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3
Q

gram stain colours

A

gram-positive bacteria: purple/violet

gram-negative bacteria: pink/red

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4
Q

what (and what colour) does iodine stain?

A

starch grains (blue-black)

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5
Q

what colours does methylene blue stain what?

A

nucleus: dark blue (+ve charge of dye attracted to -ve charge of DNA)
cytoplasm: light blue

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6
Q

purpose of staining

A

increase contrast to identify different cell types and/or organelles

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7
Q

two types of stains

A
  • simple
  • differential
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8
Q

simple stain with example

A
  • one stain used
  • uniformly stains all structures of cell
  • used to measure cell size but not to identify organelles
  • e.g. methylene blue
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9
Q

differential stain with example

A
  • multiple stains used
  • used to differentiate different organelles
  • e.g. gram stain
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10
Q

negative stain technique

A

dye with a -ve charge repels -ve charged organelles + materials (usually stains cytoplasm so organelles stand out)

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11
Q

four advantages of electron microscopes

A
  • shoes details of organelles
  • higher resolution
  • higher magnification
  • two types (TEM + SEM)
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12
Q

six disadvantages of electron microscopes

A
  • large (not portable)
  • affected by magnetic fields
  • preparation of specimens is lengthy and require expertise
  • preparation can distort specimen
  • images are black and white
  • expensive (to buy and operate)
  • vacuum is required
  • specimens must be dead
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13
Q

what types of images do SEM and TEM each make

A

SEM: 3D images of surfaces

TEM: 2D images of cross sections

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14
Q

order of microscopes increasing in resolution and magnification

A
  • light
  • SEM
  • TEM
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15
Q

ultrastructure

A

features of a cell which can be seen using an electron microscope

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16
Q

artefacts

A

visible structural detail caused by the processing of a specimen (not part of the actual specimen) e.g. air bubble trapped under cover slip or distortion of membranes from preparation for e- microscopes

17
Q

wet mount steps

A
  • pipette a drop of water on the middle of a slide
  • using tweezers, place specimen on top of water droplet
  • add a drop of iodine solution
  • place a cover slip over the sample by slowly lowering it from an angle (to avoid air bubbles)
  • dab excess liquid from the edges
18
Q

membrane of a permanent cell vacuole

19
Q

nucleus vs nucleolus

A

nucleolus contains the DNA, RNA and proteins is within the nucleus (some cells have more than one nucleolus)

20
Q

features that are present in all bacteria

A
  • cytoplasm
  • plasma membrane
  • cell wall (made of peptidoglycan)
  • 70s ribosomes
  • circular DNA
21
Q

features that are present in some bacteria (but not all) and their purpose

A
  • slime capsule (protection)
  • plasmid DNA
  • infold in membranes (absorb phosytnetic substrates or fix nitrogen)
  • flagellum (motion)
  • pili (attached to other cells or surfaces + sexual reproduction)
22
Q

intrinsic vs extrinsic proteins

A

intrinsic proteins spam the whole phospholipid bilayer

extrinsic proteins only span one layer of the phospholipid bilayer OR lie on the surface

23
Q

components of a plasma membrane

A
  • phospholipids
  • intrinsic/extrinsic proteins
  • channel proteins
  • carrier proteins
  • glycoproteins
  • glycolipids
24
Q

three components of the cytoskeleton

A
  • microfilaments
  • microtubules
  • intermediate fibres
25
what are microfilaments and their function?
- contractile fibres made of actin (protein) - cell movement and contraction (e.g. cytokinesis)
26
what are microtubules and their function?
- globular tubulin proteins polymerise to form tubes - maintain cell structure and shape - move organelles and vesicles around cells (e.g. spindle fibres)
27
what is the function.of intermediate fibres?
- give mechanical strength to cells and maintain integrity (e.g. skin cells)
28
what theory shows the plasma membrane structure and why?
- fluid mosaic model - fluid because the phospholipid molecules are flexible and free to move around each other - mosaic because the embedded proteins vary in size, shape and position
29
are channel and carrier proteins active/passive?
channel: passive carrier: passive or active
30
function of glycolipids
cell markers/antigens
31
functions of glycoproteins
- receptors for neurotransmitters or drugs - receptors for peptide/non-steroid hormones
32
where does cholesterol go in the membrane?
- lipid with a hydrophilic end and a hydrophobic end - hydrophilic end interacts with hydrophilic phosphate heads - hydrophobic end interacts with the hydrophobic fatty acid tails
33
how does cholesterol maintain fluidity?
- sits in between phospholipids to prevent them from grouping too closely and crystallising - also sits in between phospholipids to hold them together in high temperatures etc (prevent gaps)
34
roles of plasma membranes
- separates cell's components from external environment - partially permeable (regulates movement of materials into and out of cell) - transport (facilitated diffusion, active/cotransport, endo/exocytosis) - cell recognition - cell attachment - cell signalling (cytokines, non-steroid hormones, drugs)
35
roles of membranes within cells (around organelles)
- improve reaction efficiency - compartmentalisation - enzymes embedded in membrane (e- carriers etc) - increase SA (thylakoid/cristae) - isolates nuclear DNA - pores allow RNA to leave - separates potentially harmful contents from cells (lysosomes containing lysozymes)
36
four factors affecting membrane fluidity
- temperature - cholesterol - fatty acid saturation - lipid packing
37
beta blockers
drugs that work by having a specific structure to bind to specific membrane receptors preventing first messengers from binding
38
how does temperature affect membrane permeability?
- increase in temp increases kinetic energy of phospholipids - phospholipids move more freely - membrane becomes more fluid therefore more permeable - AND proteins may denature, leaving gaps in membrane
39
how do solvents affect membrane permeability?
- solvents such as alcohol (non-polae alkyl chain and polar OH group) interact with the phospholipids - solvents dissolve/surround them leaving more bigger gaps in membranes therefore increasing permeability

Biology (26 decks)

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