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Biology AQA GCSE (Separate) > 1: Cell Biology > Flashcards

1: Cell Biology Flashcards

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1
Q

what do eukaryotic cells have?

A

cell membrane; cytoplasm; nucleus

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2
Q

what do prokaryotic cells have?

A

cytoplasm; cell membrane; cell wall; single DNA loop

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3
Q

how do eukaryotic and prokaryotic cells differ?

A

prokaryotes are much smaller (0.1 - 5 µm compared to 10 - 100 µm) and their genetic material is not enclosed in a nucleus.

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4
Q

what is the function of a permanent vacuole?

A

contains cell sap, which keeps the cell turgid, providing support

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5
Q

what is the function of the nucleus?

A

carries genetic information and controls what happens inside the cell

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6
Q

what is the function of the cell membrane?

A

controls the movement of substances into and out of the cell and provides protection for the cell

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7
Q

what is the function of the cell wall?

A

made of cellulose; supports and protects the cell

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8
Q

what is the function of mitochondria?

A

where most (aerobic) respiration reactions happen

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9
Q

what is the function of cytoplasm?

A

jelly-like substance; contains dissolved nutrients, salts and organelles, where chemical reactions happen

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10
Q

what is the function of chloroplasts?

A

they convert light energy into chemical energy via photosynthesis using chlorophyll

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11
Q

what is the function of plasmids?

A

additional circular loop of DNA used to transfer genetic material from one cell to another

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12
Q

what is the function of ribosomes?

A

where protein synthesis occurs

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13
Q

what is cell specialisation/differentiation?

A

the process by which generic cells change into specific cells meant to do certain tasks within the body by gaining different sub-cellular structures

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14
Q

what is the function of a phloem cell and how is it specialised to carry out that function?

A

func: carry sugars around the plant
cell walls between plants break down to form special sieve plates - allows water w dissolved foods to move freely; supported by companion cells which transfer energy needed to move dissolved food up and down the plant

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15
Q

what is the function of a xylem cell and how is it specialised to carry out that function?

A

func: carry water and mineral ions around plant, from roots
forms long hollow tubes to allow water and mineral ions to move easily; the spirals of lignin inside the xylem make them v strong and helps them withstand the pressure of water moving and supports plant stem

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16
Q

what is the function of a nerve cell and how is it specialised to carry out that function?

A

func: carry electrical impulses around the body
lots of dendrites (long tips at main part of cell) to connect to other nerve cells; long axon to carry nerve impulses from [a] to [b]; lots of mitochondria for energy needed to make chemicals

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17
Q

what is the function of a sperm cell and how is it specialised to carry out that function?

A

func: move through water/reproductive system; pass on genetic info
long tail to aid movement; lots of mitochondria to provide lots of energy;
tip stores digestive enzymes to break down outer layer of egg; large nucleus w genetic info

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18
Q

what is the function of a muscle cell and how is it specialised to carry out that function?

A

func: to contract and relax
has special proteins that slide over each other to make fibres contract; lots of mitochondria to provide energy needed for chemical reactions when cells contract and relax; can store glycogen (for aerobic respiration)

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19
Q

what is the function of a root hair cell and how is it specialised to carry out that function?

A

func: to take in water and mineral ions
greatly increased surface area for water to move into cell; large, permanent vacuole speeds up osmosis; lots of mitochondria to provide energy needed for active transport of mineral ions into cell

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20
Q

how does the differentiation of animal cells and plant cells differ?

A

most animal cells differentiate at an early stage; most plant cells retain the ability to differentiate throughout
life

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21
Q

in mature animals, cell division is mainly restricted to what?

A

to repair and replace

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22
Q

describe how microscopes have developed over time.

A

1590s - first compound (2 lenses) microscope made; thought to have magnified from ×3 to ×9.
1650 - Robert Hooke observed and drew cells using a compound microscope
Late 1600s - microscope with a single spherical lens made; magnified up to ×275.
1800s - the optical quality of lenses increased; similar to ones we use today

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23
Q

what is the maximum magnification for light microscopes?

A

around ×1500

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24
Q

what are the limits of a light microscope?

A

low magnification; low resolution of around 0.2 μm, or 200 nm

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25
Q

what are the benefits of a light microscope?

A

offers high levels of observational quality; easy to use; do not require radiation to operate; allows you to observe living organisms

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26
Q

what are the two types of electron microscope?

A

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

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27
Q

what is an SEM used for?

A

has a large field of view so can be used to examine the surface structure of specimens; often used at lower magnifications - x100,000, resolving power - 2 nm

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28
Q

what is an TEM used for?

A

used to examine thin slices or sections of cells or tissues; max. magnification - x1,000,000, resolving power - less than 1 nm

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29
Q

how has electron microscopy increased understanding of sub-cellular structures?

A

electron microscope has much higher magnification and resolving power than a light microscope; allows us to see and understand many more sub-cellular structures and study cells in much finer detail

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30
Q

what is the calculation for magnification?

A

magnification = size of image / size of real object

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31
Q

how do bacteria cells reproduce?

A

by binary fission, as often as once every 20 minutes if they have enough nutrients and a suitable temperature

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32
Q

how can bacteria be grown (for culturing)?

A

in a nutrient broth solution or as colonies on an

agar gel plate

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33
Q

why must bacteria cultures be uncontaminated when investigating the action of disinfectants and antibiotics?

A

presence of competing species can affect the growth of cultures and the validity of any study performed on them; so we can only grow the microorganism we want

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34
Q

why should Petri dishes and culture media be sterilised before use?

A

to prevent contamination

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35
Q

why must inoculating loops used to transfer microorganisms to the media be sterilised by passing them through a flame

A

so any microorganisms on the loop are killed to prevent contamination

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36
Q

why must the lid of the Petri dish be secured with adhesive tape and stored upside down?

A

prevents condensation (another form of contamination) from dropping on to the surface of the agar

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37
Q

why must school laboratories, incubate cultures should at 25°C

A

restricts growth of more harmful pathogens - more likely to grow at higher temps

38
Q

how can the effectiveness of different antibiotics, antiseptics or disinfectants be determined?

A

by calculating the area of an inhibition zone around a disc of the substance being tested

39
Q

how do you calculate the inhibition zone?

A

πr²

40
Q

what is meant by the mean division time of bacteria?

A

average amount of time it takes for a bacterial cell in a population to divide

41
Q

what does the cell number increase by for each division?

A

power of 2

so 10 divisions = x 2 to the power of 10

42
Q

describe chromosomes

A

made of DNA molecules; each carries a large no. of genes; comes in pairs (body cells)

43
Q

how many chromosomes does a typical human body cell have?

A

46 chromosomes - 23 pairs

44
Q

what is mitosis?

A

a stage in the cell cycle when the nucleus divides

45
Q

describe the growth stage of the cell

A

chromosomes double - initially remain attached to each other with each strand called a chromatid
the number of subcellular structures (such as ribosomes and mitochondria) also increases

46
Q

describe the process of mitosis

A

nucleus membrane breaks down and chromosomes line up across equator of cell; one chromosome from each set is pulled to each end of the cell, and a new nucleus forms around each group of chromosomes

47
Q

what happens after mitosis in the cell cycle?

A

the cytoplasm and cell membranes divide in a process known as cytokinesis; results in the formation of two genetically identical daughter cells

48
Q

how do you calculate how long each stage of the cell cycle lasts (given observations of how many cells are in each stage of the cell cycle)

A

length of time in stage = observed no. of cells in stage / total no. of cells observed x total length of cell cycle

49
Q

what is a stem cell?

A

an undifferentiated cell which is capable of dividing to many more undifferentiated stem cells; from these cells, other cells can arise through the process of differentiation

50
Q

what are the different types of stem cells?

A

animals: embryonic stem cells, adult stem cells; plants - meristem cells

51
Q

describe the source, potential and products of embryonic stem cells.

A

found on the inside layer of the embryo; potential - undifferentiated/unspecialised; can produce all different types of specialised cell found in the body

52
Q

describe the sources, potentials and products of adult stem cells.

A

all: limited ability to differentiate/ partially specialised
source 1: bone marrow - can produce mainly cells of blood (rbcs, cell of immune system)
2: skin - can produce cells found in different layers of the skin, hair follicles
3: other organs e.g. liver, brain - can produce cells found in respective organs
4: umbilical cord blood - can produce cells of blood (rbcs, wbcs), muscle and nerve tissue

53
Q

describe the source, potential and products of meristem cells.

A

found in the tips of roots and shoots (growing parts of plant); potential - fully undifferentiated; one cell has the ability to divide to produce a whole new plant

54
Q

what are the roles of embryonic stem cells?

A

to form all of the different tissues and organs needed during development to form a new individual

55
Q

what are the roles of adult stem cells?

A

predominantly to replace cells lost through damage or to produce new cells for growth; but bone marrow has to continually make new blood cells throughout life

56
Q

what are the roles of meristem cells?

A

to differentiate into the cells needed by the plant in regions where growth is occurring

57
Q

what is therapeutic cloning and why is it used?

A

when an embryo is produced with the same genes as
patient; stem cells from the embryo are not rejected by the patient’s body so can be used for medical treatment (without patient having to take drugs to suppress their immune system)

58
Q

how can treatment with stem cells treat the conditions, diabetes and paralysis?

A

diabetes: stem cells could differentiate into insulin-producing pancreatic cells which are transplanted into patient’s body
paralysis: stem cells could differentiate into neurons which are transplanted into damaged region of nervous system

59
Q

what are the benefits of using stem cells in medicine?

A

large potential to treat a wide variety of diseases; organs developed from patient’s own stem cells reduces risk of organ rejection and the need to wait for a matching organ donation; adult stem cells are already used successfully in a variety of treatments

60
Q

what are the risks/issues of using stem cells in medicine?

A

stem cells cultured in lab could become infected w virus which could be transmitted to patient; risk of cultured stem cells gaining mutations that can lead them to develop to cancer cells; low number of stem cell donors

61
Q

what are the social issues of using stem cells in medicine?

A

is possible for embryonic stem cells to be collected before and after birth (umbilical cord blood) and stored in a clinic, but expensive; lack of peer-reviewed clinical evidence of success of stem cell treatments

62
Q

what are the ethical issues of using stem cells in medicine?

A

stem cells may be sourced from unused embryos (for IVF) - embryo cannot consent, who decides? ; religious beliefs rejecting interference w process of human reproduction

63
Q

how can meristem cells be used?

A

to produce clones of plants quickly and economically

64
Q

what can cloning of plants be used for?

A

to clone rare species at risk of extinction as a result of human activity to protect them and maintain biodiversity - gives scientists more time to study them to see if they can produce any compounds of interest; but plants produced are clones, so numbers increase, but genetic diversity within clones is low
to clone crop plants with special features e.g. disease or pest resistance to produce large numbers of identical plants for farmers - reduces the need to use chemicals e.g. pesticides (environmental benefits)

65
Q

what are three transport processes that living organisms use for exchange?

A

diffusion, osmosis and active transport

66
Q

what is diffusion?

A

the net movement of particles in a fluid from an area of higher concentration to an area of lower concentration

67
Q

is diffusion active or passive?

A

passive

68
Q

what does the movement of particles in a fluid is depend on?

A

how much kinetic energy they have - higher the temp., more kinetic energy particles have and the faster they can move by diffusion

69
Q

why can’t starch diffuse into a cell?

A

it is too large to pass through the partially permeable membrane

70
Q

when do substances diffuse into the cell? (2 examples)

A

Oxygen - aerobic respiration

Carbon dioxide - into photosynthesising plant cells for photosynthesis

71
Q

when do substances diffuse out of the cell? (2 examples)

A

urea - highly toxic; diffuses out to be excreted by kidneys

carbon dioxide - product of aerobic respiration

72
Q

what is diffusion driven by?

A

concentration gradient

73
Q

what three factors affect diffusion?

A

difference in concentration - the greater the difference in concentration, the faster the overall rate of diffusion
temp. - the higher the temp, the more kinetic energy particles have, the faster the rate of diffusion
surface area of membrane separating the two regions - the greater the surface area, the greater the rate of diffusion across it

74
Q

how does the surface area to volume ratio affect diffusion rate?

A

a greater ratio means the distance between cell membrane and centre of the cell, is relatively low- substances do not have to travel very far to get where they are needed

75
Q

what happens to the sa : v ratio as an organism increase?

A

it decreases.

76
Q

why is there a need for exchange surfaces and

a transport system in multicellular organisms?

A

small sa:v ratio; distance between surface of organism to centre is relatively large; larger organisms have exchange surfaces and transport systems as diffusion, osmosis and active transport cannot happen sufficiently to meet a larger organism’s needs - so to maximise the exchange of materials

77
Q

how is the small intestine adapted for exchange?

A

needs to allow digested food to be absorbed to blood stream across wall
adaptions : has a highly folded surface which is lined with specialised intestinal epithelial cells (which also have a highly folded cell membrane) - increases SA;
only one layer of epithelial cells covers surface of each villus - decreases diffusion distance; each villus has a good blood supply - maintains a concentration gradient

78
Q

how are the lungs adapted for exchange?

A

need to allow gas exchange between air in alveoli and the blood, to supply cells with oxygen for aerobic respiration and to remove carbon dioxide
adaptations : millions of alveoli - collectively increases SA; wall of each alveolus is one cell thick, with a moist lining and excellent blood supply - maintains a concentration gradient

79
Q

how are fish gills adapted for exchange?

A

need to allow gas exchange between water flowing through gills and blood, to supply cells with oxygen for aerobic respiration and to remove carbon dioxide
adaptations: each gill is made from lots of smaller plates called filaments, which are also covered in projections called lamellae - increases SA; dense capillary network => a good blood supply flows in the opposite direction to water passing through the gills - maintains a concentration gradient

80
Q

how are root hair cells adapted for exchange?

A

needs to absorb water and mineral ions from the soil and anchor the plant
adaptations : root network is highly branched - increases SA; surface of the roots are covered in root hair cells, which have a specialised structure with root hair projections - increases SA

81
Q

how are leaves adapted for exchange?

A

needs to photosynthesise - requires efficient gas exchange between air surrounding the leaf and the photosynthetic cells, whilst minimising water loss
adaptations : stomata predominantly cover the lower side of the leaf, allowing air to circulate inside the leaf - decreases diffusion distance for carbon dioxide and oxygen; lower layer of the leaf is made from spongy mesophyll cells which allow air to circulate inside the leaf

82
Q

list four ways the effectiveness of an exchange surface can be increased.

A

having a large surface area; a membrane that is thin, to provide a short diffusion path; (in animals) having an efficient blood supply - to reduce distance of exchange of materials between cells and the bloodstream and to move substances towards or away from exchange surfaces to maintain concentration gradients; (in animals, for gaseous exchange) being ventilated

83
Q

what is osmosis?

A

the diffusion of water molecules from a dilute solution to a concentrated solution through a partially permeable membrane

84
Q

describe the practical to observe movement of water by osmosis.

A

place two similar pieces of plant tissue into solutions with differing concentrations (at least 5) for set time
measure the mass & the length of each potato cylinder before & after it has been submerged in solution – dependent variables needed to calculate the percentage change in mass & length
independent variable - concentration of salt/sucrose solution in mol dm3
control variables - type & volume of solute in solution, temperature, & time

85
Q

describe what the different results of the osmosis practical mean.

A

if the plant tissue gains mass: water moved into the plant tissue from the solution surrounding it by osmosis - solution is more dilute than the plant tissue
if plant tissue loses mass: water moved out of the plant tissue into the solution by osmosis - solution is more concentrated than the plant tissue
if no overall change in mass: no net movement of water as the concentration in both the plant tissue and the solution must be equal - water still moving into and out of the plant tissue, but no net movement in this case

86
Q

how do you calculate percentage change for the osmosis practical.

A

(final mass - initial mass) / initial mass x 100
positive percentage change means potato has gained water by osmosis => the solution is more dilute, a negative percentage change suggests the opposite

87
Q

what is active transport

A

movement of substances from a more dilute solution to a more concentrated solution (against a concentration gradient) - requires energy from respiration

88
Q

why is active transport necessary in plants?

A

need to move minerals from a region of lower concentration (the very dilute solution of minerals in the soil surrounding the roots) to a region of higher concentration (inside the cytoplasm of the cell);
mineral ions are needed by plants to function healthily

89
Q

how does active transport take place?

A

by protein carrier molecules embedded in the cell membrane

90
Q

why is active transport necessary in animals?

A

Active transport allows sugar e.g. glucose to be transported into the bloodstream from the lumen of the small intestine when the concentration of sugar molecules in the blood is higher
sugar molecules are used in respiration to release energy for cells to function

91
Q

where does osmosis occur?

A

between all cells and their immediate surroundings; particularly between cells and bloodstream

92
Q

why do athletes opt to drink sports drinks over bottled water after competing?

A

they are designed to help replace water, salts (ions/electrolytes) and glucose lost from the body during exercise; v important that the balance between ions and water is correct between the cells of the body and the bloodstream - imbalance could mean body’s cells work inefficiently:
if there is too little water in the blood or the blood ion concentration is too high: cells will lose too much water by osmosis and shrink/dehydrate
if the concentration of water in the blood is too high or the ion concentration is too low, cells will absorb too much water, swelling & possibly bursting

Biology AQA GCSE (Separate) (5 decks)

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