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GCSE Biology > Cell Biology > Flashcards

Cell Biology Flashcards

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1
Q

what are eukaryotic cells?

A

Complex cells. Eg Animal and plant cells

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2
Q

what are prokaryotic cells?

A

single-celled organisms. Eg bacteria

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3
Q

List the different parts of an animal cell:

A
  • nucleus
  • cytoplasm
  • cell membrane
  • mitochondria
  • ribosomes
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4
Q

what is the purpose of the nucleus?

A

contains genetic material, and controls cells activity

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5
Q

what is the purpose

of the cytoplasm?

A

A gel-like substance, where most of the chemical reactions happen. Contains enzymes that control these reactions

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6
Q

what is the purpose of a cell membrane?

A

to hold the cell together and control what goes in and out

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7
Q

what is the purpose of the mitochondria?

A

where most of the reactions for respiration take place

respiration transfers the energy which the cells need to work

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8
Q

what is the purpose of the ribosomes?

A

where proteins are made in the cell

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9
Q

What EXTRA sub-cellular structures do plant cells have, in addition, to those of animal cells?

A

rigid cell wall - cellulose, supports & strengthens
permanent vacuole - contains cell sap ( solution of sugar and salts)
chloroplasts - where photosynthesis occurs, has chlorophyll

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10
Q

Describe the structure of a bacteria cell

A
  • cytoplasm
  • cell membrane
  • cell wall
  • singular circular strand of DNA
  • plasmids

NO chloroplasts of mitochondria

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11
Q

what is a light microscrope?

A

a microscope which uses light and lenses to form an image of a specimen and magnify it.
We are able to see individual cells, and large subcellular structures

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12
Q

what are electron miscroscopes microscopes?

A

microscopes that use electrons to form an image, have higher magnification that kight microsopes

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13
Q

list some benefits of electron microsopes:

A
  • higher resolution
  • higher magnification
  • we can see smaller thing sin greater detail ( v small sub-cellular structures)
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14
Q

define resolution

A

the ability to distinguish between two points

higher resolution = sharper image

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15
Q

magnification =

A

image size / real size

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16
Q

How do you use a light microscope to look at a slide? ( 6 steps)

A

1 - clip the slide you have prepared onto the stage
2 - select the lowest powered objective lense
3 - use coarse adjustment knob to move the stage up to just below the objective lens
4 - look down the eyepiece. use the coarse adjustment knob to move the stage downwards until the image is roughly in focus.
5 - adjust the focus with the fine adjustment knob, until you get a clear image of what is on the other slide
6) if you need to see the slide with a greater magnification, swap to a higher-powered objective lens and refocus

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17
Q

how do you prepare a microscope slide? ( onion practical)

A

1) add a drop of water to the middle of the clean slide
2) cut up onion, and separate into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers
3) using tweezers place the epidermal tissue into the water on the slide
4) add a drop of iodine solution, it is a stain. Stains are used to highlight objects in a cell by adding colour to them
5) place a coverslip on top.

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18
Q

what are the key things in a miscrosope drawing?

A

you need:

  • a title
  • proportional subcellular structures
  • labelled important features
  • no colouring or shadng
  • take up at least half the space given
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19
Q

what is diffferentiation?

A

the process by which a cell changes to become specialised for its job

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20
Q

do most plant cells ever loose their ability to differentiate?

A

no

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21
Q

cells that differentiate in mature animals are aminly used for…

A

repair and preplacing cells

eg skin or blood cells

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22
Q

what is the term for an undifferentiated cell?

A

stem cell

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23
Q

Describe what a sperm cell is specialised for, and how so.

A

specialised for: reproduction
function: get male DNA to female DNA
how its specialised:
- long tail and streamlined head helps it swim to the egg
- lots of mitochondira to provide it with energy needed
- carried enzymes to digest through egg cell membrane

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24
Q

Describe what a nerve cell is specialised for, and how so.

A

specialised for: rapid signalling
function: to carry electrical signaals from one part of the body to another
how its specialised:
- long, to cover long distances
- branched connections at he ends to connect other nerve cells and form a netweok throughout the body

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25
Q

Describe what a muscle cell is specialised for, and how so.

A 
specialised for: contaction
function: to contract quickly 
how its specialised: 
- long, so have space to contract
- contain lots of mitochondria to generate energy needed for them to contract
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26
Q

Describe what a root hair cell is specialised for, and how so.

A

specialised for: water and minerals
how its specialised:
- grow into long”hairs” which stick into the soil. This increases the plants surface area for absorbing water and mineral ions from soil

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27
Q

Describe what pholem and xylem cells are specialised for, and how so.

A

specialised for: transporting substances

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28
Q

what are chromosones?

A

coiled up lenths of DNA molecules

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29
Q

how many pairs of chromosones does a human cell have?

A

23 pairs

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30
Q

what do organisms use mitosis for?

A

for growth and to replace damaged cells

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31
Q

Describe the first stage of the cell cycle:

Growth and DNA replication

A

1) in a cell thats not dividing the DNA is spread out in long strings
2) cell grows and increases the number of subcellular strucutes
3) cell duplicates its DNA - when copied it forms X shaped chromosones, and each “arm” is one copy

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32
Q

Describe the second ( and final :D ) stage of the cell cycle:

M I T O S I S

A

1) the chromosones line up at the centre of the cell and the cell fibres pull them apart. An arm of each chromosone goes to opposite ends of the cell
2) membranes form around each of the sets of chromosones. They become the nuclei of the new cells - the cell has split
3) cytoplasm and cell membrane divide

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33
Q

describe the products of mitosis

A

2 daughter cells, genticallu identical to parent cell and to eachother

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34
Q

describe the process of binary fission:

4 steps

A

1) circular DNA and plasmids replicate
2) the cell gets bigger and the circular DNA strands move to opposite poles of the cell
3) cytoplasm begins to divide, new cell walls begin to form
4) cytoplasm divides producing 2 daughter cells

35
Q

describe the duaghter cells produced during binary fission

A

x2, one copy of circular DNA, variable number of plasmids

36
Q

what are good conditions for bacteria to grow in?

A

warm environemnt, lots of nutrients

37
Q

what do culture mediums contain?

A

carbohydrates, minerals, proteins, and vitamines

38
Q

what forms can culture mediums be in?

A
  • nutrient broth solution

- agar jelly

39
Q

describe how bacteria will grow on agar plactes

A

they will form visible colonies on the surface of the jelly and will spread out to give an even covering of bacteria

40
Q

describe how to make and use an agar plate.

A
  • to make one hot agar jelly is poured into shallow round plastc dished called petri dishes
  • jelly cools and sets
  • inoclulating loops or a dropping pipette are used to transfer microrganisms to the culture medium
  • microrganisms then multiply
41
Q

describe the practical used to investigate antibiotic resistance

A

1) place paper discs soaked in differnet types of antibiotics on an agar plate, that has an even covering of bacteria. leave space between discs.
2) antibiotics will diffuse into jelly. bacteria resistant will continue to grow, but the non resistant will die. A clear area, called the inhibition zone, will show where the bacteria has died
3) leave the plate for 48 hours at 25 degrees celcius
4) more effective the antibiotic - larger the inhibition zone

42
Q

You should use a control when doing the antibiotic resistance experiment. What is a control?

A

a paper disk not soaked in antibiotic

this means you can be sure the bacteria growth is affected by the antibiotic alone, not something else ( like the paper)

43
Q

how do you avoid usinng contaminated cultures?

A
  • sterilise petri dishes to keep away microrganisms
  • sterilise inoculating loop by putting it through a flame
  • lightly tape lid of the petri dish to stop air getting in
  • store petri dished upside down - to stop drops of condensation falling on agar surface
44
Q

how can you compare the effectiveness of the antibiotics in the antibiotic resisitanc eexperiment?

A
  • look at the relative sizes of the inhibition zones

larger inhibition zone - more effective antibiotic is against the bacteria

you can do this by eye, or with the equation of a circle

45
Q

what is differentiation?

A

the process bu which a cell changed to become specialised for its job

46
Q

what is an undifferentiated cell called?

A

a stem cell

47
Q

where are stem cells found?

A

early human embryos, bone marrow

48
Q

why are the stem cells found in bone marrow different from embryonic stem cells?

A

Can only turn into certain types of cells, like blood cells

49
Q

stem cells from embryos and bone marrow can be grown in a lab to produce …

A

clones, or to differentiate for medicine or research

50
Q

what is theraputic cloning?

A

when an embryo could be made to have the same genetic information as the patient. So the stem cells produced would have the same genes and wouldn’t be rejected by the patients body if used to replace faulty cells.

51
Q

what are the risks of using stem cells in medicine?

A
  • stem cells grown in lab may become contaminated with a virus which could then be passed onto the patient and they could become sicker
52
Q

why are some people against stem cell research?

A
  • they beieve the embryos have the potential for human life
53
Q

why are some people for stem cell research?

A
  • some people think curing thosee suffereing is more important than the rights of the embryo
  • embryos used are often unwanted from fertility clinics, so would have be thrown away anyways
54
Q

where are stem cells found in plants?

A

meristems

55
Q

how long can the cells in the meristem tissue fifferentiate for?

A

the plants whole life

56
Q

what can plant stem cells be used for?

A
  • to produce plant clones quickly and cheaply
  • to grow more plants of a rare species
    ( stop them getting wiped out)
  • grow identical crops with desirable features, eg disease ressitance
57
Q

define diffusion.

A

Diffusion is the spreading out of particles from an area f higher concentration to an area of lower concentration

58
Q

how does the concentration gradient ( the difference in concentration) affect the rate of diffusion?

A

the bigger the concentration gradient, the faster the rate of diffusion

59
Q

In what way does temperature affect diffusion? why?

A

a higher tempertaure gives a fater difffusion rate, because the marticles have more energy, so move around faster

60
Q

what kind of molecules cn fit through cell membranes?

A

very small ones, such as glucose, amino acids and water

61
Q

how does the surface area of the cell mebrane affect the diffusion rate?

A

the larger the surface area the faster the diffusion rate, because more particles pass through at once.

62
Q

what is osmosis?

A

osmosis is the movement of water molecules across a partially permeable membrane from a region of higher cocentration to lower concentration

63
Q

what is a partially permeable membrane?

A

a membrane with very small holes in it

64
Q

osmosis is a type of passive…

A

diffuison

65
Q

describe an experiment to demonstrate osmosis

A

1) cut up a potato into identical cylinders and place into beakers with different sugar solutions: one should be pure water, another a very concentrated sugar solutions, and then some in between
2) measure mass of cylinders, then leave for 24hrs
3) take out, dry with a paper towel and measure mass again
4) calculate percentage change in mass, plot graph etc.

66
Q

potato experiment question:

if the cylinders have drawn in water via osmosis what will happen to their mass?

if water has been drawn out of the cylinders by osmosis

A

take in water - mass will increase

give out water - mass will decrease

67
Q

what is active transport?

A

when subststances are absorbed against the concentration gradient

68
Q

describe how root hair cells are adapted for active transport?

A

each branch of the root is covered in millions of microscopic hairs, which gives the plant a large surface area for absorbing water and mineral ions from the soil

69
Q

why do root hair cells need to use active transport?

A

In order to absorb minerals and water, which are essential for healthy growth. The concentration of minerals is usually higher in the root hair cells than in the soil, so diffusion cannot be used.

70
Q

what does active transport need, that diffusion doesn’t?

A

energy

71
Q

active transport happens in humans when taking glucose from….

A

the gut and kidney tubules

72
Q

describe why active transport is used when there is a lower concentration of nutrients in the gut, but a higher concentration in the blood

A
  • the concentration gradient is the wrong way, so active transport is used
  • active transport allows nutrients to be taken into the blood
  • this means that glucose can be taken into the bloodstream when its concentration is already higher than in the gut. It can then be transported to cells where its used for respiration
73
Q

how easy it is for an organism to exchange substances with its environment depends on the organisms ..what?

A

surface area to volume ratio.

74
Q

in single celled organisms gases and dissolved substances can diffuse directly into teh cell across the cell membrane. Why?

A

because they have a large enough surface area compared to their volume, so enough sunstances can be supllied across the cell membrane to supply the volume of the cell

75
Q

how are exchange surfaces adapted to maximise effectiveness?

A
  • thin membrane, short distance to diffuse
  • large surface area, so lots of sunstance can diffuse at once
  • in animals there are lots of blood vessels, to get stuff in and out of blood quickly
  • gas exchange surfaces in animals are often ventialated
76
Q

what is the job of the lungs in gas exchange?

where does the gas exchange take place?

A
  • to transfer oxygen to the blood and to remove waste carbon dioxide from it
  • in the alveoli ( millions of lil air sacs in the lungs)
77
Q

how are the alveoli specialised to maximise the diffusion of oxygen and carbon dioxide?

A
  • enormous surface area
  • moist lining ( for dissolving gasses)
  • very thin walls
  • good blood supply
78
Q

there are projections are on the inside of the small intestines, that increase its surface area. What are these called?

A

villi

79
Q

how are villi adapted to be a good exchange surface?

A
  • single layer of surface cells

- very good blood supply to assist quick absorption

80
Q

what are stomata?

A

tiny holes on the exchange surface of a leaf that let carbon dioxide diffuse in, and oxygen and water vapour diffuse out

81
Q

what are guard cells?

A

cells that control the size of the stomata, which close the stomata is the plant is losing water faster than it is being replaced by the roots. without these cells the plants would wilt.

82
Q

how are the walls of the cells inside the leaf adapted to be an exchange surface?

A

the air spaces inside the leaf increase the area of its surface so there is more chance for carbnd dioxide to get into cells

83
Q

describe the function of gills in fish

A

they are an exchange surface. Water ( containing oxygen) enters through the mouth and passes out through the giils. As this happens oxygen diffuses from the water into the blood in the gills, and carbon dioxide diffuses from the blood into the water

84
Q

how are fish gills adapted as a good exchange surface?

A
  • each gill is made ofloads of thin plates called gill filaments which increase the surface area for the exchange of gases
  • the filaments are covered in lots of tiny structures called lamellae which increase the surface area more
  • the lamellae have lots of blood capillaries, and a thin layer of surface cells

GCSE Biology (8 decks)

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