paper two Flashcards
(101 cards)
1
Q
what is cell differentiation?
A
the process by which a cell changes to become specialised for its job
2
Q
where are stem cells found?
A
early human embryos and bone marrow
3
Q
can embryonic stem cells turn into any cell?
A
yes
4
Q
can adult stem cells turn into any cell?
A
no
5
Q
what happens during differentiation?
A
some genes are ‘switched off’ (silened) so they can’t be transcribed which ensures that the only proteins produced in the specialised cell are the ones needed to carry out its particular job
6
Q
what can stem cells be used for?
A
they can be used to treat many different diseases, repair damaged tissues, and even grow new organs for transplant
7
Q
what are the risks of growing stem cells in the lab?
A
they could become contaminated with a virus which could then be passed on to the patient and make them sicker
8
Q
why are some against stem cell research?
A
- morally object because the cells could’ve become a human
- uncertain about possible long term effects
9
Q
what do plants diffuse in/out during the day?
A
- make more oxygen in p/s than is used in respiration
- so release oxygen
- use up more co2 in p/s than they produce
- so they take in co2
10
Q
what do plants diffuse in/out during the night?
A
- during night, plants only respire bc not enough light for p/s
- so take in oxygen and release co2
11
Q
what do the air spaces in the leaf do?
A
let gasses like co2 and oxygen move easily between cells + increases surface area for gas exchange
12
Q
what do the stomata do when in gets dark?
A
they close bc p/s can’t happen so they don’t need to let co2 in and it stops water escaping so the plant won’t dry out
13
Q
what do the stomata do when the water supply to the roots dries up?
A
they close to prevent the plant drying up, but it means there is no photosynthesis
14
Q
which cells control the opening and closing of the stomata?
A
the guard cells
15
Q
how does a root hair cell take up water?
A
through osmosis
16
Q
why do the hairs help plants take up water through the roots?
A
they increase the surface area
17
Q
what is transpiration?
A
the evaporation and diffusion of water vapour from the surface of a plant
18
Q
where does most transpiration happen?
A
the leaves
19
Q
what causes more water to be drawn up through the xylem?
A
transpiration, as it creates a slight shortage of water in the rest of the leaf so the water in the xylem is drawn up to fill it - there is a constant transpiration stream of water through the plant
20
Q
how does light intensity affect transpiration?
A
the higher light intensity, the greater the transpiration rate bc stomata begin to close as it gets darker (bc p/s can’t happen in the dark so they don’t need to let in co2), so very little water can escape
21
Q
how does temperature affect transpiration?
A
the warmer it is, the greater the rate of transpiration because the particles have more kinetic energy to evaporate and diffuse out of the stomata
22
Q
how do you investigate transpiration?
A
- set up a potometer
- cut leafy shoot under water to prevent xylem closing
- use vaseline at the joints of potometer to reduce water loss
- set up the necessary environmental factors (temp=temp controlled room/water bath, humidity = wrap in plastic bags with different concentrations of water, windspeed = fan, light intensity = lamp at different distances)
- record starting place of air bubble on scale
- leave it for 1 hour
- record the final position of air bubble, work out distance moved, work out water absorbed
23
Q
how does wind speed affect transpiration?
A
the higher the wind speed, the greater the rate of transpiration bc water vapour in the air is blown away so there is a low concentration of water particles outside the leaf so water moves via osmosis (diffuses quickly)
24
Q
how does humidity affect transpiration?
A
the lower the humidity, the faster the rate of transpiration bc low humidity means low concentration of water particles so diffusion/osmosis is faster
25
what are platelets?
small fragments of cells that help blood clot
26
what do blood clots do?
- prevent you losing too much blood
- prevent harmful pathogens/microorganisms entering thr bloodstream through the wound
27
what is the process of blood clots forming?
- when the platelet is exposed to oxygen, they release clotting factors/chemicals
- chemicals produced cause the soluble plasma protein fibrinogen to be changed into the insoluble fibrous protin fibrin
- fibrin forms a network of fibres across the cut, which trap platelets and red blood cells
- this forms a clot or a scab
- can happen in a blood vessel if plaques cause red blood cells to be broken (which can cause heart attacks)
- also clotting factors cause the platelets to become sticky and adhere to the damaged area to form a sort of plug
28
how do vaccinations work?
- normally lymphocytes take a while to produce the antibodies
- vaccinations normally involve injecting dead or inactive pathogens which carry antigens
- these trigger an immune response and lymphocytes produce memory cells which remain in the blood for a long time
- so if live pathogens of the same type enter the blood, antibodies will be produced much faster and in greater quantities
29
what is the filtered liquid in the bowman's capsule known as?
the glomerular filtrate
30
what is reabsorbed in the nephron?
all the glucose, all the amino acids, some water, some mineral ions
31
where does selective reabsorption happen?
the proximal and distal convoluted tubule
32
what happens when the kidneys reabsorb more water?
the urine has a smaller volume and is more concentrated
33
what hormone controls how much water is reabsorbed by the kidneys?
ADH
34
what does ADH do?
more ADH makes the collecting duct more permeable to water so more water is reabsorbed back into the blood
35
what is the structure of the urinary syste?
- kidneys
- ureters
- bladder
- urethra
36
what mechanism is osmoregulation controlled by?
negative feedback
37
what does urine contain?
- water
- urea
- ions
38
what part of the brain detects the water content of the blood?
the hypothalamus
39
what gland secretes the ADH?
the pituitary gland
40
what happens when the water content of the blood is too low?
- hypothalamus detects low levels of water in the blood
- stimulates pituitary gland to secrete more ADH
- collecting duct becomes more permeable
- more water is reabsorbed via osmosis into blood capillaries
- vol of urine decreases, concentration increases
41
how is the PCT adapted for selective reabsorption?
lots of mitochondria for ATP for active transport, thin membrane for short active transport distance
42
what vessel transports blood to the glomerulus?
the renal artery
43
what is the source of ADH?
pituitary gland (in the brain)
44
what is the role of ADH?
controls water content
45
what is the source of FSH?
pituitary gland
46
what is the role and effect of FSH?
- female sex hormone
- causes the follicle and ovum to mature in an ovary
- stimulates ovaries to produce oestrogen
47
what is the source of LH?
pituitary gland
48
what is the role and effect of LH?
- female sex hormone
- starts ovulation; stimulates the release of an egg from the follicle in the ovary to the fallopian tubes
49
what is the shape of DNA?
two strands which form a double helix
50
what are the two strands of DNA held together by?
bases
51
what are the four bases?
- adenine
- cytosine
- guanine
- thymine
52
what is the complementary base pairing rule?
A - T
C - G
53
how many strands is an RNA molecule?
one strand
54
what bases does RNA have?
- adenine
- cytosine
- guanine
- uracil
55
what does DNA do?
stores the genetic information and controls cell activities
56
what is DNA made up of?
nucleutides: a sugar (deoxyribose), a phosphate, and a nitrogenous base
57
how are the nucleotides in DNA joined together?
by covalent bonds between the sugar of one nucleotide and the phosphate group of the next (which forms the sugar phosphate backbone)
58
how does DNA differ from RNA?
- RNA is single stranded, DNA is double stranded
- RNA has a sugar called ribose while DNA has a sugar called deoxyribose
- RNA has the base uracil (U) while DNA has the base thymine (T)
- RNA is shorter i think
59
what are the two types of RNA?
- messenger RNA (mRNA)
- transfer RNA (tRNA)
60
where is mRNA formed?
the nucleus
61
where is the tRNA found?
the cytoplasm
62
what is the process of transcription?
- the two strands of DNA are unzipped by the enzyme helicase
- the enzyme RNA polymerase attaches to the DNA just before the gene
- the RNA polymerase moves along the DNA strand. free RNA nucleotides are attached to (and form hydrogen bonds with) the exposed DNA strand nucleotides by base pair rule
- RNA polymerase then catalyses the formation of covalent bonds between RNA nucleotides to form a strand of mRNA
63
what is the process of translation?
- the mRNA strand travels through the cytoplasm and attaches to the ribosome
- the tRNA connect to the mRNA
- the tRNA transport amino acids
- the ribosome enzymes catalyses the covalent bond between the amino acids
- the used tRNA molecules leave the ribosome to collect more amino acids
- forms peptide
64
what does it mean if an area of DNA is non-coding?
it doesn't code for any amino acid
65
what does it mean if a characteristic is caused by a codominant allele?
neither allele is recessive so characteristics from both alleles are shown (eg blood group AB instead of blood group A or B)
66
what effect do most genetic mutations have on the phenotype?
most have no effect, but some have a small effect and rarely they have a significant effect
67
what can increase the incidence of mutations?
- exposure to ionising radiation (eg gamma rays, x-rays, UV rays)
- exposure to chemical mutagens (eg chemicals in tobacco)
68
what mutations would have no effect on the phenotype?
- mutations that occur in unimportant regions of dna, or if the mutated codon still codes for the same amino acid (degenerate nature), or if the mutation occurs in a recessive allele
69
how many amino acids are there?
20
70
what is biodiversity?
a measure of the variety of different species of organisms living in a habitat
71
are more biodiverse habitats more or less stable?
more stable
72
what are examples of human actions which reduce biodiversity?
- deforestation
- pollution
- global warming (not really an action but yk)
73
how do you use belt transects to study distribution across a habitat?
- mark out a line in the area you want to study
- collect data using quadrats placed next to each other
- count all the organisms of the species you're interested in
- or record other data eg mean height of plant or abiotic factors in each quadrat (eg. measure light with light meter)
- repeat several times and find a mean no. of organisms or mean % covered for each quadrat
- plot a graph to see if the abiotic factor is correlated with change in distribution
74
what is denitrification?
nitrates being made into N2 gas in the atmosphere by denitrifying bacteria
75
what is nitrogen fixation?
N2 in the air being turned into plant proteins (CHON) by nitrogen fixing bacteria in the roots nodules of legumes
or
N2 in the air being made into intrates/ammonium ions by nitrogen fixing bateria in the soil
or
lightning because it has enough energy to make nitrogen react with oxygen in the air to give nitrates
76
what do decomposers do in the nitrogen cycle?
break down proteins (in rotting plants and animals) and urea (in animal waste) and turn them into ammonia which forms ammonium ions in the soil
77
what is nitrification?
ammonium being turned into nitrites by nitrifying bacteria then those nitrites being turned into nitrates by nitrifying bacteria
78
what are the four main effects of deforestation?
- leaching
- disturbing the balance of carbon dioxide and oxygen
- soil erosion
- disturbing evapotranspiration
79
what is leaching?
- normally, the trees (/plants) take up water
- after deforestation, water isn't taken up by plants so can begin to run off from the soil into rivers and lakes
- mineral ions dissolve into the soil water so are leached away with the water
- nutrients in soil aren't replaced, so the soil becomes infertile
80
what is soil erosion?
- tree roots hold the soil together
- no trees means the rain can carry away some of the topsoil (erosion)
- topsoil contains the most fertile, mineral ion rich materials so when it is lost, the minerals are too
- causes the soil to become infertile and reduces the chance of plants regrowing
81
what is evapotranspiration?
the process of water evaporating from the earth's surface and from plant transpiration
82
how does deforestation disturb evapotranspiration?
- less trees mean less transpiration so less evapotranspiration
- so less water is put into the atmosphere
- so less rain
- which can cause droughts and makes the local climate drier
83
how does deforestation affect the carbon cycle?
- forests take up co2 by photosynthesis and store it in wood and slowly release it when they decompose
- when trees are cut down and burnt, all the co2 is released at once
- this leads to more co2 in the atmosphere which contributes to global warming
- also less trees means less photosynthesis so less oxygen in atmosphere and more co2
84
what does interspecific mean?
between different species
85
what does intraspecific mean?
within one species
86
why are fish kept in cages? (same thing with nets/fences i think)
- to stop them using as much energy swimming about
- prevents interspecific predation
87
how are fish fed and why?
- they are fed a nutritious diet that is high in lipids and proteins so they grow quicker and bigger
- regular feeding with small amounts so more food gets eaten (which reduces waste)
88
why are fish separated by age?
- larger fish will out compete smaller individuals for food or even prey on the smaller individuals (prevents intraspecific predation)
89
why do fish farmers use selective breeding?
to produce less aggressive, faster growing fish
90
how do fish farmers prevent diseases and parasites?
- fish are given antibiotics
- can be treated with pesticides
- biological pest control is also used
- dead or infected fish are removed quickly
91
why are freshwater fish farmed in tanks?
- conditions can be controlled eg water quality
- temperature, pH and oxygen level can be monitored
- easier to control food
- easier to keep the water clean/remove the waste
92
how do fish farmers maintain the quality of the water?
- they filter the water to remove waste and harmful bacteria to prevent diseases
- water can also be filtered to maintain high oxygen levels for aerobic respiration
93
what methods can fish farmers use to remove waste products?
- Water can be filtered to remove waste products such as faeces and sewage
- Fences, nets and tanks can be cleaned to minimise exposure to Waste
- Location of Fish can be changed to ensure clean Water
94
what effects can fish farms have on the environment?
- fish could escape and outcompete or interbreed with local species which can reduce biodiversity and/or upset the local ecosystem
- parasites or pathogens can be introduced into ecosystems by farmed fish
- excess feed and waste from fish can cause eutrophication
95
how can eutrophication caused by fish farming be reduced or prevented?
- limiting feed
- clearing waste
- bubbling oxygen through water
96
what is used to clone plants?
micropropagation
97
what is the process of micropropagation?
- a plant with desirable characteristics is picked
- small pieces (called explants) are taken from the tips of the stems and the side shoot of the plant
- the explants are sterilised
- then the explants are grown 'in vitro' - they're placed in a petri dish containing a nutrient medium (which also contains growth hormones)
- cells in the explants divide and grow into a small plant
- the small plants are taken out of the medium, planted in soil and put into glasshouses
98
what are the advantages of micropropagation?
- greater yield
- faster growth
- propagation of rare species
- practicable any time of year
- genetic modifications can be passed on to the rest of the population efficiently
99
what are the disadvantages of micropropagation?
- population is genetically identical so susceptible to disease
- vulnerable to change in conditions
- decreases variation
100
what is the process of cloning in sheep? (and all mammals)
- a diploid body cell is taken from sheep A (the one you want to clone)
- the diploid nucleus of sheep A's cell is removed
- an egg cell is taken from sheep B
- the egg cell is enucleated
- diploid DNA from sheep A is inserted into the enucleated egg cell and fused together
- an electric shock is used to stimulate division by mitosis
- mitosis allows the cell to form an embryo
- embryo is implanted into the uterus of sheep C (preferably a sheep which has given birth before) which acts as a surrogate
101
why are transgenic animals cloned?
to ensure that the useful genetic characteristic is passed on bc it isn't always with normal breeding
