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GCSE Biology > Topic 1: Cell biology > Flashcards

Topic 1: Cell biology Flashcards

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1
Q

what are all living things made of?

A

cells

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2
Q

what are eukaryotic cells?

A

complex cells like animal and plant cells

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3
Q

what are eukaryotes?

A

organisms made from eukaryotic cells

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4
Q

what is a prokaryote?

A

a single prokaryotic cell

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5
Q

what sub cellular structures do animal cells gave?

A

1) nucleus - contains genetic material that controls and activates the cell
2) cytoplasm - gel like substance where chemical reactions happens it contains enzymes that control the reaction
3) cell membrane - holds the cell together and controls what goes in and out
4) mitochondria - where aerobic respiration happens
5) ribosomes - where proteins are made

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6
Q

what cellular structures do plants cells contain?

A

all the same ones as animal cells as well as…

1) rigid cell wall - made of cellulose
2) permanent vacuole - contains cell sap
3) chloroplasts - where photosynthesis happens they contain chlorophyll which absorbed light

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7
Q

what are bacteria?

A

prokaryotes

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8
Q

what cellular structures does bacteria cells contain?

A

1) cell membrane
2) cell wall
3) strand of DNA instead of nucleus
4) plasmids which are rings of DNA
5) cytoplasm

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9
Q

what do microscopes do?

A

allow us to see very small things

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10
Q

what is a light microscope?

A

microscopes that use light and lenses to form an image and magnify it they let us see individual cells and sub cellular structure

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11
Q

what are electron microscopes?

A

microscopes that use electrons to form a image

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12
Q

what are the the advantages of electron microscopes?

A

they have higher resolution

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13
Q

what is the formula for magnification?

A

magnification = image size / real size

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14
Q

a specimen is 50 um wide calculate the width of the image of the specimen under magnification of x 100 five the answer in mm?

A

image size = magnification x real size
100 x 50
5000 um = 5mm

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15
Q

a mitochondria is approximately 0.0025 mm long write this in standard form?

A

2.5 x 10 to the power of -3

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16
Q

REQUIRED PRACTICAL: how to prepare a onion on a microscope slide?

A

1) add a drop of water to the middle of a clean slide
2) cut up an onion and separate it out into layers use tweezers to peel off some epidermal tissue from the bottom of one layer
3) using the tweezers place the epidermal tissue into the water on the slide
4) add a drop of iodine solution (a stain) which highlights the cell by adding color
5) place a cover slip on top try not to get any bubbles on the specimen

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17
Q

REQUIRED PRACTICAL: how to look at a slide through a microscope?

A

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

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18
Q

REQUIRED PRACTICAL: how do you draw what you see through a microscope?

A

1) draw what you see under the microscope using a pencil and sharp point
2) make sure your drawing take up at least half of the space available and that it is drawn with clear unbroken lines
3) your drawing should not include coloring or shading
4) if you are drawing cells the sub cellular structures should be in proportion
5) remember to include a title of what you were observing and write down the magnification you where looking at it at
6) label the important features using straight uncrossed lines

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19
Q

what is cell differentiation?

A

the process when a cell changes to become specialized for its job

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20
Q

when do cells differentiate?

A

in an animal early in their life and they then lose the ability to differentiate however in plants the cells do not use the ability do differentiate

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21
Q

when do cells differentiate in an adult?

A

repairing and replacing cells like skin and blood

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22
Q

how are sperm cells specialized for reproduction?

A
  • long tail
  • streamlined head
  • lots of mitochondria to supply energy
  • contains enzymes to digest the egg membrane
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23
Q

how are nerve cells specialized for rapid signalling?

to carry electrical signals

A
  • long

- branched connections

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24
Q

how are muscle cells specialized for contraction?

A
  • long

- lots of mitochondria to supply energy

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25
Q

how are root hair cells specialized for absorbing water and minerals?

A

-big surface area

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26
Q

how are pholem and xylem cells specialized for transporting substances?

A
  • long
  • connected end to end
  • hollow in the center
  • very few sub-cellular structures
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27
Q

what are chromosomes?

A

coiled up lengths of DNA molecules

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28
Q

what does the nucleus contain?

A

genetic information in form of chromosomes

29
Q

what is mitosis?

A

the stage when a cell divides

30
Q

what happens in the growth and DNA stage of the cell cycle?

A

1) in a cell that is not dividing the DNA is all spread out in long strings
2) before it divides the cell has to grow and increase the amount of sub cellular structure such as mitochondria and ribosomes
3) it then duplicates its DNA - so there’s one copy for each new cell the DNA is copied and forms X-shaped chromosomes each arm is a duplicate of the other

31
Q

what happens in the Mitosis stage of the cell cycle?

second half

A

4) the chromosomes line up at the center of the cell and cell fibers pull them apart the two arms of each chromosome go to the opposite end of the cell
5) membranes form around each of the sets of chromosomes these become the nuclei of the two new cells - the nucleus has divided
6) lastly the cytoplasm and cell membrane divide the cell has now produced two daughter cells they both contain the same DNA they are identical and also to the parent cell

32
Q

how do prokaryotic cells reproduce?

A

by binary fission

33
Q

what happens in binary fission?

A

1) the circular DNA and plasmid( s) replicate
2) the cell gets bigger and the circular DNA strands move to opposite ‘poles’ of the cell
3) the cytoplasm begins to divide and new cell walls begin to form
4) the cytoplasm divides and two daughter cells are produced each daughter cell has one copy of the circular DNA but can have a variable number of the copies of the plasmid(s)

34
Q

a bacteria cells mean division time of 30 mins how many cells would it have produced in 2.5 hours?

A

2.5 x 60 = 150
150 / 30 = 5 divisions
2 to the power of 5 = 32 cells

35
Q

REQUIRED PRACTICAL: how do you grow bacteria in the lab?

A

1) bacteria is grown in a “culture medium” which contains the carbohydrates minerals proteins and vitamins they need to grow
2) the culture medium used can be a nutrient both solution to solid agar jelly
3) bacteria grown on agar plates will form visible colonies on the surface of the jelly or will spread out to give an uncovering of bacteria
- to make an agar plate hot agar jelly is poured into shallow round plastic dishes called petri dishes
- when the jelly’s cooled and set inoculating loops can be used to transfer microorganisms to the culture medium alternatively a sterile dropping pipette and spreader can be used to get an even cooling of bacteria
- the microorganisms then multiply
4) in the lab at school cultures of microorganisms are not kept above 25 degrees Celsius because harmful pathogens are likely to grow at temperatures above that
5) in industrial conditions cultures are incubated at higher temperatures so they grow faster

36
Q

REQUIRED PRACTICAL: how do you investigate the effect of antibiotics on bacteria growth?

A

1) place paper discs soaked in different types of antibiotics on a agar plate that has an even covering of bacteria leave some space between the discs
2) the antibiotic should diffuse into the agar jelly antibiotic-resistant bacteria that are not effected by the antibiotic will continue to grow on the agar around the paper discs but non-resistant strains will die a clear area will be left where the bacteria have died this is called the inhibition zone
3) make sure you use a control this is a paper disc that has not been soaked in an antibiotic instead soak it in sterile water you can then be sure that difference between the growth of the bacteria around the control disc and around one of the antibiotic discs is due to the effect of the antibiotic alone
4) leave the plate for 48 hours at 25 degrees celcius
5) the more effective the antibiotic is against the bacteria the larger the inhibition zone will be

37
Q

REQUIRED PRACTICAL: how do you avoid contamination?

A

1) the petri dishes and culture medium must be sterilized before use to kill any unwanted microorganisms that may be lurking on them
2) if an inoculating loop is used to transfer the bacteria to the culture medium it should be sterilized first by passing it through a hot flame
3) after transfering the bacteria the lid of the petri dish should be lightly taped on
4) the petri dish should be stored upside down - to stop condensation falling on the agar surface

38
Q

REQUIRED PRACTICAL: how do you calculate the size of the inhibition zone to compare results?

A

you can compare the effectiveness of different antibiotics on bacteria by looking at the relative sizes of the inhibition zone
the larger the inhibition zone around the disc the more effective the antibiotic is against the bacteria
you can do this by eye if there is a large difference in size but you get more accurate results its a good idea to calculate the area of the inhibition zone using their diameter

39
Q

what is the formula to work out the area of an inhibition zone?

A 
area = pi x radius squared 
pi = 3.142
40
Q

the diagram below shows the inhibition zone produced by antibiotics A and B use the areas of the inhibition zone to compare the effectiveness of the antibiotics
diameter of…
A = 14mm
B = 20mm

A

formula = pi x radius squared
14 / 2 = 7mm radius
20 / 2 = 10mm

are of…
A = 3.142 x 7 squared = 154mm squared
B = 3.142 x 10 squared = 314mm squared
the inhibition zone of antibiotic B is roughly twice the size of the inhibition zone of antibiotic A

41
Q

what is differentiation?

A

the process by which cells becomes specialized

42
Q

what are undifferentiated cells called?

A

stem cells

43
Q

where are stem cells found?

A

early human embryos

44
Q

how can you produce clones?

A

stem cells can be grown in a lab

45
Q

how can stem cells be used to cure diseases?

A
  • stem cells from an adults bone marrow can replace faulty blood cells
  • you could use embryonic stem cells can be used to replace faulty ones in sick people
46
Q

what is therapeutic cloning?

A

when a embryo is made to have the same genetic information as the patient so the cells wont be rejected when put in the body

47
Q

what are disadvantages of transferring stem cells?

A

they may become contaminated by viruses in the lab

48
Q

why are some people against stem cell research?

A
  • fell that human embryos should be used for experiments

- against religion

49
Q

why are some people in favor of stem cell research?

A
  • some think it is the right embryos to cure patients

- most embryos used are unwanted ones

50
Q

where are stem cells found in plants?

A

the meristems

51
Q

what can stem cells in plants be used for?

A
  • cloning
  • grow more plants of rare species
  • grow disease resistance
52
Q

what is diffusion?

A

the net movement of particles from places of high concentration to places of low concerntration

53
Q

where does diffusion happen?

A

in gases and solutions

54
Q

what speeds up diffusion?

A
  • a high concentration gradient

- higher temperatures

55
Q

what substances can diffuse through cell membranes?

A

very small ones eg oxygen and glucose

56
Q

what is osmosis?

A

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

57
Q

what is a partially permeable membrane?

A

a membrane with very small holes in it

58
Q

REQUIRED PRACTICAL: osmosis observing the effects of sugar solutions on plant tissues?

A

1) you cut up an innocent potato into identical cylinders and get some beakers with different sugar solutions in them one should be pure water and another should be very concentrated sugar solutions (eg 1 mol/dm3)
then you can have a few others with concentrations in between (eg 0.2 mol/dm3, 0.4 mol/dm3, 0.6 mol/dm3, ect)
2) you measure the mass of the cylinders then leave one cylinder in each beaker for 24 hours or so
3) then you take them out dry them with a paper towel and measure the mass again
4) if the cylanders have drawn in water by osmosis, they’ll have increase in mass if water has been drawn out then they’ll have a decrease in mass you can calculate the percentage change in mass then plot a few graphs and things
5) the dependent variable is the chip mass and the independent variable is the concentration of the sugar solution all other variables must be kept the same so the experiment is fair
6) like any experiment you need to know of how errors may arise some times they may occur when carrying out the method eg if some potato cylinders where not fully dried you can reduce the errors by doing the experiment multiple times

59
Q

what is active transport?

A

when minerals are absorbed against a concentration gradient

60
Q

how do plants use active transport?

A

root cells cannot take up minerals by diffusion because their are more minerals inside the root hair so they must use active transport instead

61
Q

how does active transport stop us starving?

A

sometimes there is a lower concentration of nutrients in the gut than in the blood therefore active transport must be used to transfer glucose

62
Q

when is diffusion used to take in and transfer out nutrients?

A
  • oxygen and carbon dioxide are tranfered between cells and the environment during gas exchange
  • in humans urea diffuses from cells into blood plasma for removal from cells to plasma
63
Q

what is the surface area to volume ratio in a hippo represented by a 2cm x 4cm x 4cm block?

A 
surface are = l x w 
2 x 4=64cm squared 
volume = l x w x h
2 x 2 x 4=32
so the ratio is 64:32 = 2:1
64
Q

how are exchange surfaces adapted to maximize gas exchange?

A
  • thin membrane so shorter distances to diffuse
  • they have large surface area so lots of a substance can diffuse at once
  • lots of blood vessels to get stuff in and out of the body quickly
  • gas exchange surfaces in animals are often ventilated
65
Q

how are alveoli adapted for gas exchange?

A
  • large surface area
  • a most lining
  • very thin walls
  • good blood supply
66
Q

what do the aveoli do?

A

they transfer oxygen from the lungs to the blood and removes carbon dioxide

67
Q

what do villi do?

A

increase surface area so digested food can be absorbed quickly

68
Q

how is a leaf adapted for gas exchange?

A
  • underneath the leaf their is an exchange surface
  • it has small holes for carbon dioxide to go through called stomata
  • the size of the stomata is controlled bu guard cells
  • the leaf is flat increasing surface area
69
Q

how are gills in fish adapted for gas exchange?

A
  • oxygen diffuses from water into the blood in the gills
  • each gil is made from thin plates called gil filaments which give a big surface area
  • gil filaments are covered in structures called lamellae which increase surface area
  • thinn surface layer of cells to shorten the distance they have to travel
  • large concentration gradient between water and blood

GCSE Biology (4 decks)

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