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BIOLOGY > 1.1 Cell Structure > Flashcards

1.1 Cell Structure Flashcards

1
Q

what are the two types of cells?

A
  • eukaryotic (plant and animal)
  • prokaryotice (bacteria)
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2
Q

what are the differences between eukaryotic and prokaryotic cells?

A

prokaryotic cells are much smaller than eukaryotic cells.
eukaryotic cells contain membrane bound-organelles and a nucleus containing genetic material, wile prokaryotes do not.

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3
Q

what is the prokaryotic cell wall composed of?

A

peptidoglycan

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4
Q

how is genetic information stored in a prokaryotic cell?

A

found free within the cytoplam as:
- chromosomal DNA (single large loop of circular DNA)
- plasmid DNA

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5
Q

what are plasmids?

A
  • small, circular loops of DNA found free in the cytoplasm and separate from the main DNA.
  • carry genes that provide genetic advantaged e.g. antibiotic resistance.
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6
Q

what is the order of magnitude?

A

a power to the base 10 used to quantify and compare size.

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7
Q

what is a centiemetre (cm)?

A

1 x 10^-2 metres

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8
Q

what is a millimetre (mm)?

A

1 x 10^-3 metres

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9
Q

what is a micrometre (μm)?

A

1 x 10^-6 metres

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10
Q

what is a nanometre (nm)?

A

1 x 10^-9 metres

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11
Q

what is the difference in order of magitude between a human hair (length = 100μm) and the HIV virus (length = 100nm)?

A

100μm = 10^-4m
100nm = 10^-7m
-4-(-7) = -4 + 7 = 3

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12
Q

list the components of both plant and animal cells (5)

A
  • nucleus
  • cytoplasm
  • cell membrane
  • mitochondria
  • ribosomes
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13
Q

list the additional cell components found in plant cells (3)

A
  • chloroplasts
  • permanent vacuole
  • cell wall
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14
Q

other than storing genetic informationm, what is the function of the nucleus?

A

controls cellular activites

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15
Q

describe the structure of the cytoplasm

A
  • fluid component of the cell.
  • contains organelles, enzymes and dissolved ions and nutrients.
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16
Q

what is the function of the cytoplasm?

A

site of cellular reactions e.g. first stage of respiration.
transport medium.

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17
Q

what is the function of the cell membrane?

A

conrols the entry and exit of materials into and out of the cell.

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18
Q

what is the function of the mitochondria?

A

site of later stages of aerobic respiration in which ATP is produced.

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19
Q

what is the function of the ribosomes?

A

joins amino acids in a specific order during translation for the synthesis of proteins.

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20
Q

what is the plant cell wall made of?

A

cellulose

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21
Q

what is the function of the plant cell wall?

A
  • provides strength.
  • prevents the cell bursting when water enters by osmosis.
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22
Q

what does the permanent vacuole contain?

A

cell sap (a solution of salts, sugars and organic acids).

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23
Q

what is the function of the permanent vacuole?

A

supports the cell, maintaininmg its turgidity.

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24
Q

what is the function of chloroplasts?

A

site of photosynthesis

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25
Q

describe how sperm cells in animals are adapted to their function

A
  • haploid nucleus contains genetic information.
  • tail enables movement.
  • mitochondria provides energy for tail movement.
  • acrosome contains enzymezs that digest the egg call membrane.
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26
Q

describe how nerve cells in animals are adapted to their function

A
  • long axon allows electrical impulses to be transmitted all over the body from the central nervous system.
  • dendrites from the cell body cannot to and receive impulses from other nerve cells, muscles and glands.
  • myelin sheath insulates the axon and speeds up the transmission of impulses along the nerve cell.
27
Q

describe how muscle cells are adapted to their function

A
  • arrangement of proteins filaments allows them to slide over each other to produce muscle contraction.
  • mitochondria to provide energy for muscle contraction.
  • merged cells in skeletal muscle allow muscle fibre contraction in unison.
28
Q

describe how root hair cells in plants are adapted to their function

A
  • large surface area to absorb nutrients and water from surrounding soil.
  • thin walls that do not restrict water absorption.
29
Q

describe how xylem cells in plants are adapted to their function

A
  • no upper or lower margins between cells to provide a continuous route for water to flow.
  • thick, woody wide walls strengthen their structure and prevent collapse.
30
Q

describe how ploem cells in plants are adapted to their function

A
  • sieve plates let dissolved amino acids and sugars be transported up and down the stem.
  • companion cells provide energy needed for active transpor of substanced along the phloem.
31
Q

what is cell differentiation?

A

the process by which cells become specialised.

32
Q

why is a cell differentiation important?

A

allows production of different tissues and organs that perform various vital functions in the human body.

33
Q

at what point in their life cycle do most animal cells differentiate?

A

early in their life cycle

34
Q

for how long do plant cells retain the ability to differentiate?

A

throughout their entire life cycle

35
Q

what is the purpose of cell division in mature animals?

A

repair and replacement of cells

36
Q

what changes does a cell go through as it differentiates?

A

becomes specialised through acquistion of different sub-cellular structures to enable a specific function to be performed by the cell.

37
Q

define magnification

A

the number of times bigger an image appears compared to the size of the real object.

38
Q

define resolution

A

the smallest distance between two objects that can be distinguished.

39
Q

how does a light microscope work?

A

passes a beam of light through a speciment which travels through the eyepiece lens, allowing the specimen to be observed.

40
Q

what are the advantages of light microscopes? (4)

A
  • inexpensive
  • easy to use
  • portable
  • observe both dead and living specimens
41
Q

what is the disadvantage of light microscopes?

A

limited resolution

42
Q

how does an electron microscope work?

A

it uses a beam of electrons which are focused using magnets. the electrons hit a fluorescent screen which emits visible light, producing an image.

43
Q

name the two types of electron microscope

A

transmission electron microscope (TEM)
scanning electron microscopes (SEM)

44
Q

what is the advantage of electron microscopes?

A

greater magnification and resolution.

45
Q

why do electron microscopes have greater magnification and resolution?

A

they use a beam of electrons which has a shorter wavelenght than photons of light.

46
Q

how have electron microscopes enabled scientists to develop their understandng of cells?

A
  • allow small sub-cellular structures (e.g. mitochondria, ribosomes) to be observed in detail.
  • enable scientists to develop more accurate explanations about how cell structure relates to function.
47
Q

what are the disadvantages of electron microscopes? (4)

A
  • expensive
  • large so less portable
  • require training to use
  • only dead speciments can be observed
48
Q

how can the magnification of an image by calculated?

A

magnification = size of image/size of real object

49
Q

what is standard form?

A

a way of expressing numbers - written as a figure between 1 and 10 multiplied by a positive or negative power of 10.

50
Q

write 0.005 in standard form

A

0.005 = 5 x 10^-3

51
Q

write 10382 in standard form

A

10382 = 1.0382 x 10^4

52
Q

how do bacteria multiply?

A

binary fission (simple cell division)

53
Q

how often do bacteria multiply?

A

once every 20 mintues if enough nutrients are available and the temperature is suitable.

54
Q

state 2 ways in which bacteria can be grown

A
  • nutrient broth solution
  • colonies on an agar gel plate
55
Q

what nutrients make up a nutrient broth solution?

A

all nutrients required for bacteria to grow including nitrogen for proteing synthesis, carbohydrates for energy and other minerals.

56
Q

what are uncontaminated cultures of microorganisms needed for?

A

investigating disinfectant and antibiotic action.

57
Q

describe the preparation of an uncontaminated culture using aseptic technique

A
  1. use pre-sterilised plastic petri dishes or sterilise glass petri dishes and agar gel before using with an autoclave.
  2. pour the sterile agar gel into the petri dish and allow time to set.
  3. sterilise the inoculating loop by passing it through a bunsen burner flame.
  4. dip the inoculating loop into the solution of microorganisms and make streaks with the loop on the surface of the agar.
  5. put the lid on the petri dish and secure it with tape. label accordingly then turn and store upside down.
  6. incubate the culture at 25°c in school laboratories.
58
Q

why must petri dishes and culture media before sterilised before use?

A

to kill any bacteria already present.

59
Q

why must inoculating loops be sterilised by passing them through bunsen burner flame?

A

to kill any bacteria present on the inoculating loop.

60
Q

why must the petri dish lif be secured with adhesive tape and the whole dish stored upside down?

A

stops bacteria in the air contaminating the culture.
the lid is not fully sealed to prevent the growth of anaerobic bacteria in a lack of oxygen.
upside down to prevent condensation from forming and dripping down onto the colonies.

61
Q

why are cultures incubated at 25°c in school laboratories?

A

harmful pathogens are less likely to grown at this temperature.

62
Q

what is the formula used to calculate cross-sectional area of a bacterial colony or clear area around a bacterial colony?

A

πr^2
= 3.14
r = radius (diameter/2)

63
Q

how is the number of bacteria in a population after a certain time calculated from the mean division time?

A
  1. calculate the number of times the bacteria will divide in the given time period from the mean division time.
  2. use the following equation to calculate the number of bacteria:
    number of bacteria in population at the end of time period = number of bacteria at the beginning of the time period x 2^number of divisions in the time period.
    express the anwer in standard form is possible.
64
Q

calculate the number of bacteria that will be present after 3 hours for a population that divides every 15 minutes and has 5 bacterium present now

A

15 minutes = 0.25 hours
3/0.25 hours = 12 divisions
5 x 2^12 = 20480 or 2.048 x 10^4

BIOLOGY (34 decks)

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