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Biology > 12.5 Studying Cells > Flashcards

12.5 Studying Cells Flashcards

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1
Q

what is a cell

A

the basic unit of life

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2
Q

all cells in multicellular organisms will have the same…

A

basic structure

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3
Q

in the organism a cell will be related to its…

A

function

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4
Q

eukaryotic cell definition

A
  • ‘true nucleus’
  • DNA of eukaryotes is enclosed by a nuclear membrane
  • cells have membrane bound organelles
  • linear DNA molecules coiled around histone proteins to form chromatin
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5
Q

all eukaryotic cells

A

plants, algae, animal, protozoan, fungi

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6
Q

4 eukaryotic kingdoms

A

1 animalia
2 plantae
3 protoctista (algae, protozoa)
4 fungi (unicellular yeast cells)

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7
Q

plant cells have…

A

CELLULOSE cell walls

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8
Q

what do algal cells contain

A

chloroplasts -> photosynthesis
(protoctista)

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9
Q

characteristics of fungi

A
  • multi-cellular fungi have cells joined -> long hyphae
  • cell walls made from CHITIN
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10
Q

draw and label an animal cell (eukaryotic)

A
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11
Q

what’s the difference between a mitochondrion and mitochondria

A

mitochondrion (singular)
mitochondria (pleural)

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12
Q

draw and label a plant cell (eukaryotic)

A
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13
Q

draw and label a chloroplast (plants / algae)

A
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14
Q

5 things in a chloroplast

A
  • granum
  • thylakoid membrane
  • stroma
  • starch grains
  • DNA and ribosomes
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15
Q

function of granum

A

stack of thylakoid membranes

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16
Q

function of thylakoid membrane

A

contains chlorophyll for photosynthesis & ATP synthase enzyme to produce ATP

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17
Q

function of stroma

A

fluid filled part, some of the photosynthetic reactions occur here

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18
Q

function of starch grains

A

the energy storage molecule in plants

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19
Q

function of DNA and ribosomes

A

contain their own DNA and 70s ribosomes for synthesis of enzymes needed for photosynthesis

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20
Q

draw and label a cellulose cell wall (plants / algae)

A
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21
Q

3 things in a cellulose cell wall

A
  • many weak H bonds between cellulose fibrils
  • micro fibrils arranged in a matrix
  • plasmodesmata (gaps in the cell walls that connect cell cytoplasm’s together)
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22
Q

function of many weak H bonds between cellulose fibrils (cellulose cell wall)

A

very strong -> limits the volume of water that can move into the cell and stops osmotic lysis (bursting)

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23
Q

function of micro fibrils arranged in a matrix (cellulose cell wall)

A

wall is permeable to most molecules unlike the membrane

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24
Q

function of plasmodesmata (gaps in the cell walls that connect cell cytoplasm’s together) (cellulose cell wall)

A

allow the easy movement of water-soluble molecules

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25
Q

key differences between plant and animal cells

A

plant cells
- cellulose cell wall
- chloroplasts present (not in roots)
- large central vacuole
- carbohydrates stored as starch
- has no centrioles

animal cells
- no cell wall
- no chloroplasts
- no large central vacuole
- carbohydrates stored as glycogen
- has centrioles

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26
Q

production, transport and release of proteins from eukaryotic cells

A
  • DNA in nucleus contains genetic code to make proteins
  • New protein is synthesised on ribosomes
  • Protein is transported though RER
  • Vesicles pinched off from the RER (with polypeptide chain inside) are transported to the Golgi apparatus
  • Vesicle fuses with Golgi membrane and contents are shed into Golgi sacs
  • Proteins are built into more complex molecules such as enzymes or glycoproteins
  • Vesicles contain modified proteins (for secretion or cell membrane) bud off at the other end of the Golgi
  • Vesicles fuse with cell membrane
  • Protein released - leaves cell by exocytosis
  • Lysosomes (contain digestive enzymes)
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27
Q

prokaryotic cell definition

A
  • ‘before nucleus’
  • do not have nucleus or other membrane bound organelles
  • DNA circular, not associated with histone proteins
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28
Q

draw and label a bacterial cell (prokaryotic)

A
29
Q

differences between prokaryotic and eukaryotic cells

A

prokaryotic
- DNA circular, not associated with histone proteins
- no membrane bound organelles (no nucleus, RER, SER, Golgi, Lysosomes)
- no true nucleus (DNA free in cytoplasm)
- smaller ribosomes (70s)
- some have capsule, 1 or more flagella / plasmids
- mesosomes for ATP synthesis
- cell wall (murein / peptidoglycan)

eukaryotic
- DNA linear, associated with histone proteins
- membrane bound organelles (mitochondria, RER, SER, Golgi, Lysosomes)
- nucleus (DNA contained within nuclear membrane)
- larger ribosomes (80s)
- no capsule
- no mesosomes (mitochondria)
- cell wall (plant -> cellulose)

30
Q

viruses definition

A
  • acellular (not cells), not alive
  • very small
  • require a living cell to replicate inside
  • no cell surface membrane
  • no organelles / cytoplasm
  • no metabolic reactions
31
Q

characteristics of viruses

A
  • contain DNA or RNA (can be single or double stranded)
  • surrounded by a protein coat (capsid)
  • has attachment proteins (enable it to bind to host cells)
  • has enzymes (uses to replicate its genetic information and insert it into the host cell DNA)
  • liquid envelope
32
Q

viruses have no organelles so they are unable to do what

A
  • unable to replicate independently
  • can’t synthesis protein / DNA to make copies of itself
  • USES THE HOST CELL’S ORGANELLES TO DO THIS
33
Q

is RNA in a:
- prokaryotic cell (bacteria)
- virus
- eukaryotic cell

A
  • YES prokaryotic cell (bacteria)
  • YES virus
  • YES eukaryotic cell
34
Q

are ribosomes in a:
- prokaryotic cell (bacteria)
- virus
- eukaryotic cell

A
  • YES prokaryotic cell (bacteria)
  • NO virus
  • YES eukaryotic cell
35
Q

is a capsid in a:
- prokaryotic cell (bacteria)
- virus
- eukaryotic cell

A
  • NO prokaryotic cell (bacteria)
  • YES virus
  • NO eukaryotic cell
36
Q

are membrane bound organelles in a:
- prokaryotic cell (bacteria)
- virus
- eukaryotic cell

A
  • NO prokaryotic cell (bacteria)
  • NO virus
  • YES eukaryotic cell
37
Q

3 microscopes

A
  • light microscope
  • transmission electron microscope (TEM)
  • scanning electron microscope (SEM)
38
Q

characteristics of light microscopes

A
  • specimens illuminated by light
  • focussed using glass lenses
  • limited magnification (more lenses -> magnification by larger amount -> loses resolution)
  • limited resolution (limited by the wavelength of light)
  • 200nm resolution (can see cells but not organelles)
39
Q

resolution definition

A

the ability to distinguish 2 objects that are close together

40
Q

key phrase to remember about the wavelength and resolution of electron microscopes

A

the shorter the wavelength of the light / electrons, the better / higher the resolution

41
Q

similarities between TEM and SEM

A
  • both use a beam of electrons to illuminate the specimen
  • focused using electromagnets
  • detected using a phosphor screen / photographic film (capture image)
  • very small wavelength (observes ribosomes - 20nm)
  • both produce images with higher resolution
42
Q

the difference between TEM and SEM

A

TEM - produces 2D images
SEM - produces 3D images

43
Q

characteristics of TEM

A
  • electrons pass / fired through specimen
  • view organelles / internal structures
  • less dense (cytoplasm) absorb less electrons -> appear lighter
  • denser areas / structures (nucleolus) absorb more electrons -> appear darker
44
Q

characteristics of SEM

A
  • electrons bounce off the surface of the specimen
  • specimen not sliced
  • images always in black and white
  • always produce 3D image
45
Q

ways to remember the electron microscopes

A

T -> Transmission -> Through
S -> Scanning -> Surface

46
Q

ILLUMINATION - comparison light and TEM

A

L -> light

T -> beam of electrons

47
Q

FOCUSED BY - comparison light and TEM

A

L -> lens

T -> electromagnets

48
Q

MAXIMUM MAGNIFICATION - comparison light and TEM

A

L -> x1500 (individual cells and some large structures - nucleus)

T -> x 500,000 (objects as small as ribosomes

49
Q

RESOLUTION - comparison light and TEM

A

L -> 200nm LOWER

T -> 1nm HIGHER

50
Q

SPECIMEMS - comparison light and TEM

A

L -> living or dead

T -> dead (they are fixed in resin and sliced very thinly. must be in a vacuum)

51
Q

STAINING PROCESS - comparison light and TEM

A

L -> easy (coloured dyes)

T -> complex (using heavy metals, can create artefacts - structures not actually there)

52
Q

2 pieces of equipment required when using an optical (light) microscope

A
  • eyepiece (lens) graticule
  • stage micrometer
53
Q

what does the eyepiece graticule do

A
  • fits onto the eyepiece lens
  • a transport ruler with numbers but has no units
54
Q

what does the stage micrometer do

A
  • a microscope slide
  • has an accurate scale (1mm in 100 divisions so 1 division is 10 μm)
  • placed on the stage
  • ## used to work out the value of each division on the eyepiece graticule, when using a certain magnification
55
Q

what is the overall job of the eyepiece (lens) graticule and the stage micrometer

A

MEASURE THE SIZE OF THE CELLS
(when you take the stage micrometer away and replace it with slides with a tissue specimen -> can measure the size of cells)

56
Q

why does cell fractionation and differential-centrifugation occur

A
  • to enable scientists to study organelle function
  • the organelles must first be separated from the cell in order to be studied
57
Q

2 stages of cell fractionation and differential-centrifugation

A
  • homogenising
  • differential centrifugation
58
Q

method for separating organelles (step 1)

A
  • tissue is homogenised in blender (liver, heart, leaf etc) to break open the cells releasing the organelles into solution.
59
Q

what 3 things must the solution be for step 1

A

ICE COLD
ISOTONIC (same water potential)
BUFFERED

60
Q

what does the solution being ice cold do

A

reduce the action of enzymes that would digest organelles

61
Q

what does the solution being isotonic (same water potential) do

A

prevents osmosis of water in or out of organelles, so organelles don’t burst (lyse) or shrivel (crenation in animals)

62
Q

what does the solution being buffered do

A

to stop pH changes which could denature proteins

63
Q

method for separating organelles (step 2)

A
  • filter the mixture to remove any large pieces of tissues / cells (cellular debris) producing a solution of suspended organelles (supernatant)
64
Q

method for separating organelles (step 3)

A

differential centrifugation of the supernatant by:
- centrifuge at high speed (high g)
- centrifuge at a higher speed / (higher g) for a longer time

65
Q

why do you first centrifuge at high speed (high g)

A

the densest organelles (nucleus) are forced to the bottom of the tube into a pellet which is removed. The supernatant can be spun again to obtain the smaller and lighter organelles

66
Q

why do you then centrifuge at a higher speed / (higher g) for a longer time

A

the next densest organelles are forced to the bottom of the tube into a pellet. the pellet is removed and can be re-suspended if required.

67
Q

method for separating organelles (step 4)

A

this process can be repeated many times, at higher speeds with each step. this separates the organelles (then molecules) according to their relative densities.

68
Q

anogram for densities

A

naughty clever monkeys like eating raspberries

Biology (10 decks)

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