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A level biology > 2.1.1 Cell structure > Flashcards

2.1.1 Cell structure Flashcards

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1
Q

What is a light microscope?

A

-uses light that passes through thin specimen to reflect an image in the objective lens
- to look at whole cells and tissues

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2
Q

What is the magnification and resolution of a light microscope?

A

magnification: 1500x
resolution: 200nm (0/2micromtr)

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3
Q

What is the magnification and resolution of a transmission electron microscope?

A

magnification: 500,000x
resolution: 0.05nm

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4
Q

What is the magnification and resolution of a scanning electron microscope?

A

magnification: 100,000x
resolution: 0.20nm

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4
Q

How does an TEM work?

A
  • passes beam of electrons through specimen
  • specimen must be thin to prevent deflection of electrons
  • denser parts of specimen absorb more electrons = appear darker = produces contrast
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4
Q

Why are TEM used?

A

to look at organelle detail

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5
Q

Why do TEM images appear different from each other?

A

The images have been cut along different planes/angles

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5
Q

How do SEM work?

A
  • the beam of electrons scan the surface of specimen
  • the beam is bounced off the surface and the electrons are detected
  • forming a 3D image = surface of specimens
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6
Q

Why are SEM used?

A

to look at cell surface

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7
Q

What are laser scanning confocal microscopes?

A
  • specimen needs to be treated with fluorescent dye
  • laser beam is reflected by the fluorescent dyes
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8
Q

Why are laser scanning confocal microscopes used?

A

to look at an object at a certain depth within the cell

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9
Q

What are the advantages of TEM?

A

high resolution images = more detail
internal structures to be seen e.g vesicles

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10
Q

What are the disadvantages for TEM?

A

-only be viewed with very thin specimens
-cannot be used to observe live specimens (vacuum)
- length treatment to prepare = artefacts
- doesnt produced coloured image

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11
Q

What are the advantages of light microscopes?

A
  • see whole cells and tissues
  • use live specimen
  • view coloured image
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12
Q

What are the disadvantages of light microscopes?

A
  • low magnification
  • low resolution
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13
Q

What are the strengths of SEM?

A
  • produce 3D image
  • used on thick specimens
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14
Q

What are the disadvantages of SEM?

A
  • lower resolution than TEM
  • cannot observe live specimens
  • no colour image
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15
Q

What are the advantages of light microscopes?

A
  • used on thick specimens
  • high resolution = observe cytoskeleton
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16
Q

What are the disadvantages of laser scanning confocal microscope?

A
  • slow process; takes a long time to obtain image
  • laser has potential to cause photodamage to cells
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17
Q

How do you prepare for light microscopes?

A

staining;
specimen becomes more visible e.g to see certain (named) organelles;
to improve contrast

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18
Q

What does acetic orcein stain?

A

DNA - dark red

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19
Q

What does Eosin stain?

A

cytoplasm - pink

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20
Q

What does Sudan black stain?

A

membranes and other lipids - black

21
Q

What type of specimen needs to be prepared for a light microscope?

A

thin specimen,
thin sections allow light to pass through;
artefacts may occur

22
Q

What is magnification?

A

the number of times larger the image is in in comparison to the object

23
Q

What is resolution?

A

the ability to distinguish between very small structures that are close together; in detail;

24
Q

Draw the units diagram?

A

cm
/10 mm x10
/1000 µm x 1000
/1000 nm x 1000

25
Q

What is found in the eyepeice?

A

eye piece graticule;
used in calibration

26
Q

What is used to calibrate the eye piece graticule?

A

a stage micrometer

27
Q

What is the formula for magnification?

A

I/AM

28
Q

What is the function of the nucleus?

A

contains the cells DNA (chromatin)

29
Q

What is the function of nuclear pores?

A
  • allows mRNA and ribosomes to travel out
  • allowing enzymes e.g DNA polymerase and signalling molecules to travel in
30
Q

What is the nucleolus?

A

dense part of nucleus = site of ribosome production

31
Q

What is the function of the nuclear envelope?

A

separates the nucleus from the cytoplasm

32
Q

What is the function of the rough endoplasmic reticulum?

A

flattened sacs of cisternae continuous from the nuclear envelope
surface covered in ribosomes
where protein synthesis occurs

33
Q

What is the function of the smooth endoplasmic reticulum?

A

dont have ribosomes on its surface
lipid and hormone production occurs here

34
Q

What is the function of the golgi apparatus?

A
  • stack of membrane bound flattened sacs
  • modifies, packages proteins into vesicles
35
Q

What is the function of a ribosome?

A

site of protein synthesis

36
Q

What is the function of the mitochondria?

A

produces ATP;
made during aerobic respiration

37
Q

What is the function of lysosomes?

A

contain powerful digestive enzymes which are used to break down materials

38
Q

What is the function of a chloroplast?

A

site of photosynthesis

39
Q

What is the function of the cell surface membrane?

A

made out of phospholipid bilayer
controls what enters and leaves the cells

40
Q

What is the function of centrioles?

A

take part in mitosis to form spindle fibres

41
Q

Where are centrioles not found?

A

in flowering plants and fungi

42
Q

What is the function of a cell wall?

A

provides structural support to cell

43
Q

What is the cell wall made of in plants?

A

celluose

44
Q

What is the cell wall made of in bacteria?

A

peptidoglycon

45
Q

What is the function of the flagella?

A

whole cell movement
made of long microtubules;
they contract

46
Q

What is the function of cillia?

A

hair like projections made from microtubules
allow movement of substances over the cell surface

47
Q

How do organelles work together to produce proteins?

A
  • nucleus produces mRNA
  • mRNA leaves nucleus via nuclear pores
  • mRNA attaches to ribosome in the cytoplasm/RER
  • once protein has been made by proteinsynthesis
  • proteins travels in vesicle and transported to golgi apparatus
  • protein is modified and packaged in vesicle (addition of carbohydrate)
  • moved towards cells surface membrane
  • released via exocytosis

also; other organelle
- mitochondria: provides ATP = needed for the cytoskeleton to contract
and move vesicle

48
Q

What is the importance of the cytoskeleton?

A

whole cell support;
movement of cilia and flagella;
changing cell shape;
moving organelles;
movement of chromosomes;

49
Q

What type of ribosomes are found in prokaryotes?

A

70s

50
Q

What is the function of plasmids?

A

circular DNA; can be passed to bacteria to exchange genetic info - through pili to surrounding bacteria

51
Q

What type of DNA is found in prokaryotes?

A

circular

52
Q

What is the role of the flagella in prokaryotes?

A

used in movement of cell
requires ATP

53
Q

What is the role of the mesosome?

A

ATP is produces at the infolded regions of cells membrane

54
Q
A

A level biology (17 decks)

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