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module two biology > cell structure > Flashcards

cell structure Flashcards

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1
Q

what are the four types of microscope?

A

• light microscopes
• transmission electron microscopes
• scanning electron microscopes
• laser scanning confocal microscopes

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2
Q

describe light microscopes

A

• poor resolution due to the long wavelength of light
• living samples can be examined and a colour image can be obtained
• observed through two lenses - objective and eyepiece lens

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3
Q

how do you use a light microscope?

A
  1. clip the slide onto the stage
  2. select the lowest powered objective lens
  3. use the coarse adjustment knob to raise the stage
  4. adjust the focus with the fine adjustment knob until a clear image is obtained
  5. swap to a higher powered lens if needed and refocus
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4
Q

what is resolution?

A

the minimum distance between two adjacent objects in which they can still be viewed as separate

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5
Q

what is magnification?

A

how many times larger the image is compared to the object

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6
Q

what is resolution determined by in optical microscopes, and electron microscopes?

A

optical microscopes: wavelength of light
electron microscopes: wavelength of electrons

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7
Q

what are dry mounts?

A

• when thin slices or whole specimens are viewed with just the coverslip on top
• e.g hair

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8
Q

what are wet mounts?

A

• when the specimens have water added to them before lowering the coverslip (a mounted needle should be used to prevent bubbles from forming or lowering coverslip at a 45° angle)
• aquatic organisms are viewed this way

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9
Q

what are squash slides?

A

• wet mounts involve you pushing down on the coverslip to allow light to pass through them
• e.g a root tip squash sample to see the chromosomes in mitosis

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10
Q

what are smear slides?

A

• slides created by using the edge of another slide to smear a sample across the slide, allowing a smooth thin specimen to be created.
• e.g blood cells in a blood sample

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11
Q

what is the difference between an eyepiece graticule and a stage micrometer?

A

• an eyepiece graticule is already fitted onto the eyepiece lens
• a stage micrometer is placed onto the stage

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12
Q

how do you calibrate the eye piece graticule ?

A

• by using a stage micrometer
1. line up the stage micrometer and eyepiece graticule
2. count how many devisions on the graticule fit onto the micrometer scale
3. each division on the micrometer is worth 10um
• e.g if two divisions fit onto one division on the micrometer you do 10/2 = 5um

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13
Q

what is the magnification formula

A

size of the image / size of the real object

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14
Q

how do transmission electron microscopes work?

A

electron beams pass through the specimen

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15
Q

what is the magnification of transmission electron microscopes

A

upto x 500, 000

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16
Q

what is the resolution of transmission electron microscopes?

A

0.5 nm

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17
Q

what are the benefits of transmission electron microscopes?

A

• high magnification and resolution
• enables intracellular details to be observed

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18
Q

what are the disadvantages of transmission and scanning electron microscopes

A

• very expensive
• black and white images produced (however artificial colour can be added)
• only dead specimens can be viewed as they are in a vacuum

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19
Q

how do scanning electron microscopes work?

A

• electrons are reflected back from the specimen and detected

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20
Q

what is the magnification of scanning electron microscopes?

A

upto 100, 000 x

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21
Q

what is the resolution of scanning electron microscopes?

A

3-10nm

22
Q

what are the benefits of scanning electron microscopes?

A

• high magnification and resolution
• 3D images are generated

23
Q

what is the magnification of light microscopes?

A

upto 2, 000 x

24
Q

what is the resolution of light microscopes?

A

200nm

25
Q

what are the benefits of light microscopes?

A

• inexpensive
• short preparation time
• easy to use
• colours and living material can be observed

26
Q

what are the disadvantages of light microscopes?

A

• limited magnification and resolution

27
Q

how do confocal laser scanning microscopes work?

A

• a laser light scans the specimen
• light is absorbed by fluorescent chemicals which are radiated back from the specimen

28
Q

what are crystal violet and methylene blue used to stain ?

A

• negatively charged materials because they are positively charged

29
Q

what are nigrosin and congo red used to stain?

A

• backgrounds as they are negatively charged so don’t stain cells allowing them to stand out

30
Q

what two stains are used for gram staining?

A

crystal violet and safrinin

31
Q

how does gram staining work for gram positive bacteria?

A
  1. crystal violet is added
  2. iodine is added to fix the stain and alcohol is used to wash away any leftover stain
  3. gram positive bacteria appear blue/purple as the stain is retained due to the thicker peptidoglycan wall absorbing the dye
32
Q

how does gram staining work for gram negative bacteria?

A

• they cannot absorb crystal violet stain as their peptidoglycan wall is too thin so they do not retain the stain due to thinner walls
1. safranin is used as a counter stain which turns them red

33
Q

what colours are gram negative and gram positive bacteria?

A

gram negative - red due to safranin
gram positive - blue/purple due to crystal violet

34
Q

what are the rules for biological drawings?

A
  1. draw in pencil
  2. title the diagram
  3. add the magnification
  4. annotate cell components
  5. do not sketch
  6. do not colour in or shade
35
Q

describe the nucleus

A

function: contains genetic information, site of ribosome synthesis and transcription
structure: surrounded by a nuclear envelope with pores, contains chromosomes and also a nucleolus which produces mRNA

36
Q

describe flagella

A

function: for mobility and sometimes a sensory organelle for chemical stimuli
structure: whip like structure containing microtubules with 9 in a circle and 2 in the middle

37
Q

describe cilia

A

function: help move substances in a sweeping motion across cell surfaces
structure: hair like projections out of cells which contain microtubules with 9 in a circle and 2 in the middle

38
Q

describe centrioles

A

function: involved in the production of spindle fibres and organisation of chromosomes in cell division
structure: made of microtubules and occur in pairs to form the centrosome

39
Q

describe the cytoskeleton

A

function: maintains cell shape and controls organelle movement in cells, is also responsible for compartmentalisation of organelles
structure: made of microfillaments which control cell movement and cytokinesis and microtubules which regulate shape and organelle movements forming spindle fibres

40
Q

describe the rough endoplasmic reticulum

A

function: protein synthesis
structure: ribosomes bound to cisternae

41
Q

describe the smooth endoplasmic reticulum

A

function: lipid and carbohydrate synthesis and storage
structure: flat cisternae

42
Q

describe the golgi apparatus

A

function: modifying proteins and packaging them into vesicles
structure: a stack of flattened stacks

43
Q

describe lysosomes

A

function: breaking down waste organelles and pathogens
structure: specialised vesicles containing enzymes

44
Q

describe the mitochondria

A

function: ATP production through aerobic respiration
structure: double membrane (inner folds to form cristae) and internal fluid called the matrix

45
Q

describe ribosomes

A

function: protein synthesis
structure: 80s in eukaryotes and 70s in prokaryotes

46
Q

describe chloroplasts

A

function: photosynthesis
structure: contains a network of membranes called thylakoids which stack to form grana and a inside fluid called stroma

47
Q

describe the cell wall

A

function: provides shape and rigidity
structure: a strong barrier on the outside of the cell membrane comprised of cellulose

48
Q

describe the large permanent vacuole

A

function: increases turgor
structure: a large central sac containing water

49
Q

what organelles are involved in the production and secretion of proteins?

A
  1. the rough endoplasmic reticulum synthesises polypeptide chains
  2. the cytoskeleton sends the polypeptide chains packaged into vesicles into the golgi apparatus
  3. the proteins are modified and packaged into vesicles in the golgi
50
Q

what are the key differences between prokaryotes and eukaryotes ?

A

• prokaryotic cells are much smaller in size
• prokaryotic cels have no membrane bound organelles
• prokaryotic cels have 70s ribosomes compared to eukaryotic 80s ribosomes
• in prokaryotes, DNA is not contained within a nucleus it’s usually in plasmids
• prokaryotic cell walls are made of murien

51
Q

what is the capsule in prokaryotic cells?

A

• a slimy later made of proteins
• preventing the bacteria from drying out and protects the bacteria from the host cells immune system

module two biology (7 decks)

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