Paper 1 + 2 Flashcards
1
Q
Explain what happens to bare rock in order for trees to grow in colonization.
A
- Pioneer species colonizes rock
- Pioneer species break up rock
- Dead plants add organic matter as they decompose.
- Trees can then grow as soil becomes deeper.
2
Q
Devise an investigation to compare species richness of plants growing under trees in deciduous woodland and coniferous woodland.
A
- Change: 10 areas in each woodland, use random number generator for coordinates.
- Measure: species in each quadrat, and then calculate total number of species present in each area and compare both areas using a t-test.
- Same: time of year, soil pH, temperature, time of day…
3
Q
Explain how microorganisms in the soil break down stems of plants.
A
- Stems contain starch/cellulose
- Microorganisms release digestive enzymes
- These break glycosidic bonds
- Glucose is produced, which microorganisms respire.
4
Q
How do antibiotics kill bacteria.
A
. Inhibit enzymes needed to make chemical bonds in cell walls - cell lysis as weakened cell wall can’t take pressure as water moves into cell by osmosis.
. Inhibit protein production by binding to bacterial ribosomes. Enzymes can’t be produced so cell cannot carry out metabolic processes for growth and development.
5
Q
Explain how genetic mutation can lead to the separation of a species
A
. Different alleles lead to new phenotypes.
. Advantageous alleles are passed onto offspring.
6
Q
Explain how a drug could have made a tumour shrink
A
. Drug stops mutant allele being expressed
. Protein is not produced
. Melanoma cells are killed
. Mitosis replaces them with normal body cells.
7
Q
Explain why frequency of allele may change from one generation to the next.
A
. Allele may undergo random mutation
. Natural selection
. Immigration/emigration
. People with condition may not have children.
8
Q
Devise an experiment to find the mean rate of respiration using woodlice
A
Organism: woodlice of same age, mass, species, source
Repeat: 3x, calculate mean, discard anomalies.
Measure: Volume of gas and calculate breathing rate
Same: temperature (water bath), time (5 minutes)
Welfare of woodlice is important.
9
Q
Describe how the structure of phospholipase allows it to hydrolyse phospholipids.
A
Primary structure determines structure of enzyme.
. Tertiary/globular shape provides as active site.
. Active site is complementary to phospholipid.
. It breaks ester bonds.
10
Q
Explain how the nervous system responds to increase in temperature.
A
Thermoreceptors detect increase in temperature in hypothalamus.
. Impulses are sent along sympathetic nervous system.
. Shunt vessels constrict, causing vasodilation
. So more warm blood will flow near skin surface.
11
Q
How does IAA cause a coleoptile to grow?
A
. Taken up by cells in zone of elongation
. Cells elongate by lowing pH in cellulose in cell walls
. Coleoptile grows towards the light.
12
Q
State the location of rhodopsin in a rod cell.
A
In the outer segment.
13
Q
Describe the role of dendrites in a neurone
A
- Form synapses with other neurons
- Receive impulses from other neurons
- Involved in summation
- Initiate action potential to cell body
14
Q
What happens to lysosomes once their contents have been digested
A
. They fuse with cell surface membrane
. Release contents by exocytosis.
15
Q
Explain how IAA contributes to phototropism
A
- IAA diffuses away from the light
- H bonds between cellulose are broken
- Cell elongates as it cannot handle water pressure
- IAA causes more elongation on dark side of stem.
16
Q
The number of rod cells per eye increases when the day length is short.
Explain the advantages to the rat of this increase.
A
. The rat will have {more hours of darkness /
longer nights}
. Rod cells work well in low light levels
. Rats need to be able to see (in dark) to {find
food / avoid predators}
17
Q
Describe the differences in the structure of a myelinated sensory neurone and a myelinated motor neurone.
A
In a sensory neurone: . Dendron is longer . Axon is shorter . Cell body is not at the end . Dendron is myelinated
18
Q
The student investigated the length of time it took sea anemones to lose their habituation.
Suggest how the student carried out this investigation
A
. Use a habituated sea anemone
. Stimulate after leaving for different amounts of time
. Repeat at each time
. Note time when tentacles withdraw.
19
Q
Define succession
A
Series of changes in organisms in a given area over time.
20
Q
Describe how water availability could be investigated in these two parts of the island.
A
- idea of {using a moisture probe / drying out soil
samples / eq} ; - idea of testing soil around plants ;
OR - idea of using rain gauge / eq ;
- idea of collecting water over a period of time ;
21
Q
Define climax community
A
. At the end of succession
. Self-sustaining community
22
Q
Explain why a climax community is stable
A
- Has high biodiversity
- Species interact in equilibrium
- There is no human influence
23
Q
Define Net Primary Productivity
A
- Rate of energy converted into biomass in plants.
- GPP - R
24
Q
Explain why there is a decrease in mass of leaves during decomposition
A
. Bacteria release digestive enzymes . Glucose is formed that is soluble/dissolves . Glucose is respired . CO2 released . Water released
25
Suggest why NPP values would be of use to a farmer who wanted to use this land for cattle.
. Cattle are herbivores
. Gain energy from NPP
. Affects yield of milk
. Change to more NPP yielding crop
26
How do ribosomes make proteins
- Protein synthesis occurs
- Ribosome holds mRNA
- Ribosome holds two tRNA
- Peptide bonds form between adjacent amino acids
27
Define non-specific immune response
. Body reacts to pathogen
. Reaction is not specific to pathogen
- E.g. lysozyme, inflammation, phagocytosis
28
Explain how phagocytosis and lysozyme action lead to antigen presentation by macrophages.
. Pathogen is taken into macrophage
. Phagosome fuses with lysosome
. Pathogen is broken down by protease enzyme
. Part of pathogen glycoprotein is presented on outer membrane of macrophage
29
Explain the importance of interferons
. Prevent viruses attaching to uninfected host cells by binding to receptors, preventing virus from entering cells
. So viruses cannot replicate + infect more cells
30
Compare genetic material of bacteria and viruses
. Bacteria have DNA, viruses have DNA or RNA
. Bacteria have circular DNA, viruses have linear DNA
. Bacteria may have plasmids, viruses do not
31
Explain how antibodies work
. Agglutination
. Neutralise toxins
. Opsonisation enhances phagocytosis.
32
Explain how lysozyme work
They have active site with specific shape to cell wall of bacteria
33
Explain the process of inflammation
- Histamine is released as a result of damaged tissues
- Histamine releases platelets
- Vasodilation, capillaries more permeable...
- Inflammation causes swelling and pain
34
How did William Withering's experiment differ to modern drug testing?
- No animal testing
- No placebo
- Small sample size
- No control
- Did not test on healthy humans
- Didn't know dose
35
Explain why habituation could be good for an animal
- wastes less energy
| - Less likely to damage themselves by retracting
36
Suggest how the presence of IAA causes cells to produce proteins.
. IAA enters cell from cytoplasm to nucleus
. Binds to transcription factor
. Activates genes
. Allows RNA polymerase to bind to promotor region.
. Active genes transcribed to produce RNA which makes protein.
37
Describe how the process of DNA replication produces two identical DNA molecules
. DNA helicase unwinds and breaks apart H bonds in DNA nucleotides.
. Free complementary nucleotides line up and join by complementary base pairing
. Hydrogen bonds form between AT, GC
. DNA polymerase makes phosphodiester bonds between nucleotides.
38
Which bond joins nucleotides in single strand of DNA?
Phosphodiester
39
Explain the effect o increasing light intensity on the current produced by a rod cell
. As light intensity increases, current produced decreases
. In light, rhodopsin breaks into opsin and retinal
. Opsin binds to channel proteins on cell surface membrane
. Sodium/ cation channels close so sodium ions cannot enter rod cell.
40
What is molecular phylogeny, and how can it be used to prove species are related?
- Studies molecular similarities in DNA base sequences in proteins to conclude evolutionary relationships between organisms
41
Woese suggested that organisms could be placed in taxonomic groups based on molecular phylogeny. Explain what is meant by this statement.
. Organisms with similar characteristics are placed in the same taxonomic group
. Taxonomic groups have specific differences
. Molecular phylogeny studies evolutionary relationship
. Molecular phylogeny studies similarities in DNA sequence in proteins.
42
Suggest reasons why the two species do not interbreed.
. Physically incompatible
. Reproductive isolation
. Different breeding times
. Do not recognize courtship displays.
43
Explain why there is likely to be a greater genetic diversity in the hybrid plants than in either of the two separate species.
. Different allleles in each population
. Each population adapted to live in different environments
. Different mutations in each population
. Hybrids inherit alleles from each species
44
Explain how the two different species of Rhododendron on Yakushima Island may have evolved from a single population of an ancestral species.
. Random mutation leads to diversity in flowering times and other plant features
. Causes reproductive isolation
. Restricted gene flow between extremes of population
. Different environmental factors in each region causing different selection pressures - plants become adapted to specific region
. Over time, allele frequency changes which leads to differences between gene pools.
45
Describe the differences between DNA and RNA
. DNA has thymine, RNA has uracil
. DNA is double stranded, RNA is single stranded
. DNA has deoxyribose, RNA has ribose
. DNA is longer
46
Describe how gene therapy could help patients with cystic fibrosis
. Use genes that code for CFTR channel protein
. Introduce genes into lung cells that produce mucus
. Using a vector via injection
. Treatment needs to be repeated
. Transcription + translation of gene produces normal CFTR protein function
47
Explain why changing the primary structure changes the protein shape
. Changes the R groups
| . Bonding will be different
48
Define Non-overlapping in terms of DNA sequences.
Each triplet is discrete.
49
Suggest an advantage for most amino acids having more than one code.
. Less chance of mutations
. Third base can be changed without effect
. No effect on resulting polypeptide.
50
The sequence of triplets on a section of DNA used to form a strand of pre-mRNA is:
A cistron
51
Describe the structure of fibrous proteins
. Insoluble
. Hydrophobic outside
. Secondary structure
. Lots of amino acid sequence repetition
52
Describe the structure of globular proteins
. Soluble
. Hydrophilic outside
. 3D folded structure
. Little repetition.
53
Collagen structure
. 3 Polypeptide chains
. Chains coiled around each other
. Cross-linking between chains from H-bonds.
54
Describe how Meselsohn and Stahl proved DNA replication was semi-conservative.
. Bacteria grown for one generation on 15N
. Then grown for one generation on 14N
. Then grown for another generation on 14N
. N used to make DNA bases in nucleotides
. At each stage membrane was disrupted, DNA sample was extracted and spun in a centrifuge
. Original generation: heavy band only lower down in the tube
. 1st generation: medium band only midway down the tube
. 2nd generation: medium and light band
. As generations continue on 14N, light band gets bigger, mid band stays the same
. Proves DNA replication is semi conservative, one strand of original is combined with one strand of new.
55
Describe how Hardy-Wenberg can provide evidence for changes in population.
. Calculate allele frequencies over a period of time
56
Explain how epigenetic changes affect the development of tissues in the embryo.
. DNA in chromosome is wrapped around histone
. Modification of histone affects binding of RNA polymerase
. Methylation of DNA affects transcription of genes
. Gene expression is altered.
57
Farmer wants to destroy woodland. What information should he collect beforehand?
. Measure biodiversity with diversity index
. Assess species richness
. Find genetic diversity of species
. Presence of any endemic/ rare species.
58
Explain the effect of changing the shape of red blood cells on oxygen intake.
. Oxygen enters cells by diffusion
. Change in shape increases diffusion distance
. Less oxygen enters cells
59
Explain how antibiotics binding to ribosomes affects production of proteins in bacteria.
. Ribosome shape is altered
. mRNA cannot bind to ribosome
. No transcription
. Protein is not synthesised.
60
Explain why new antibiotics are used to treat bacteria that are resistant to other antibiotics
. Bacteria have not been exposed to new antibiotics before
. They have become resistant to other antibiotics by natural selection
. No mutation present for resistance to new antibiotics.
61
Explain how HIV particles enter T helper cells.
. GP120 receptors bind to CD4 receptors on T cells
. Viral envelope fuses with cell membrane of T helper cell
. Viral RNA enters cell.
62
Explain why some genes show linkage and others show sex-linkage
. Sex linkage relates to genes on X/Y chromosome.
. Linkage --> genes for different characteristics on same chromosome.
. There are more genes than chromosomes.
63
Devise an experiment to calculate the effect of temperature on rate of respiration in yeast
. Change: temperature below optimum temperature
. Measure: distance coloured liquid moved in 5 minutes
. Rate = distance / time
. Keep yeast concentration + volume the same
64
What happens in the visual region when a kitten has the right eye closed during the critical period.
. Fewer synaptic connections
. By neurones to right ocular dominance column
. Left ocular dominance column had more synaptic connections to compensate.
65
Explain how a single gene can give rise to acetylcholinesterase molecules with different primary structures.
. pre-mRNA splicing
. Different exons are removed
. Producing a different sequence of amino acids.
66
Alzheimer's = loss of neurones producing acetylcholine
| Explain why inhibitors of acetylcholinesterase could be helpful in Alzheimer's treatment.
. Acetylcholinesterase breaks down acetylcholine
. The inhibitor prevents breakdown of acetylcholine
. So more acetylcholine is available to attach to the post-synaptic membrane
. Compensates for loss of acetylcholine producing neurones.
67
Define Q10 temperature coefficient
The ratio of the rate of an enzyme reaction taking place
| at temperatures differing by 10
68
How do you calculate Q10?
Rate at T + 10 / Rate at 10
69
How to calculate metabolic. rate
vol. of oxygen/mass x time
70
How are clinical trials conducted for a vaccine?
. (small groups of) healthy volunteers are given the vaccine to
test for side effects (1)
• (healthy volunteers) tested for presence of antibodies to the
virus (following vaccination) (1)
• a group of people at risk of contracting the disease is given the
vaccine (1)
• the number of people who develop the viral disease (following
vaccination) are monitored (1)
71
Explain why anti-virals binding to HIV enzymes can help patients infected with HIV
. Prevents viral replication
. T helper cells not killed
. Inhibits reverse transcriptase
. So viral DNA cannot be made from viral RNA
. Inhibits integrase
. So viral DNA cannot integrate into host DNA
72
Explain how you can modify respiration practical to measure rate of respiration in mice instead of woodlice.
. Need barrier between mouse + CO2 absorber
. Attach syringe for repeat readings
. Need units/gram for each animal
. Need more CO2 absorber
. Same temperature
. Increase size of container as mouse are bigger
73
Explain what would happen to indicator fluid in the respirometer after five hours if a culture of algae was added and the tube was covered in lightproof paper.
. Fluid would move to the left due to lower pressure
. Woodlouse and algae would still respire
. Pressure reduced as CO2 absorbed.
74
Define niche and give an example for a shrub
```
the role of an organism within its habitat
. shrubs are producers
. provides food for other organisms
. makes soil more fertile
. provides shelter for more organisms
```
75
What are the effects of smoking
. Reduced oxygen uptake
. Increased stickiness of platelets
. Increases blood pressure
. Increases risk of atheroma.
76
Describe the role of oxygen in aerobic respiration
. Last electron acceptor
. In oxidative phosphorylation
. ATP is synthesized
. Presence of oxygen allows reduction of ATP.
77
What are the two types of antibiotics and how do they work
. Bactericidal - attack cell walls + cause cell lysis
| . Bacteriostatic - Attack protein synthesis
78
State one difference between the structure of pyruvate and the structure of the acetyl group in acetyl CoA
pyruvate has 3 carbons compared to 2 carbons in acetyl
79
Give a function for collagen in the blood-gas barrier
Provide strength + flexibility
80
Explain how two species of African elephant could evolve from a common ancestor.
two populations are geographically isolated from each other (1)
therefore reduced gene flow between the two populations (1)
which leads to allopatric speciation (1)
different selection pressures leading to natural selection (1)
81
Individuals who use MDMA may develop the symptoms of depression.
MDMA use results in depletion of serotonin (1)
post synaptic membrane becomes less responsive to
serotonin / loss of receptors on post synaptic membrane (1)
serotonin levels affect mood / lack of serotonin associated
with depression (1)
82
Describe how nucleotides join together to form DNA.
phosphodiester bonds form between adjacent nucleotides via dna polymerase
83
Explain how atherosclerosis can result in damage to heart muscle.
Narrows lumen of coronary arteries
Reduces blood flow to heart muscles
Decreases aerobic respiration
84
Explain the process of inflammation
Histamine released from tissues as a result of damaged tissues
Arterioles vasodilate
Increased blood flow to site
Increased permeability of capillaries
Blood plasma enters tissues, causing swelling
85
Describe the role of tRNA in the production of leptin.
. tRNA molecules {transport amino acids to the
ribosome}
. tRNA molecule has an anticodon that binds a codon on the mRNA
. each tRNA carries a particular amino acid
86
Describe how a frameshift mutation could result in the production of leptin with a variety of shorter primary structures.
. New start/stop codon
. Changes triplet code
. Shorter amino acid sequence
87
Explain how the primary structure of trypsin molecules can be used to produce a phylogenetic tree.
. Determine sequence of amino acids
. Determine number of similarities in amino acids between species
. The more similarities, the more closely related.
88
Explain the relationship between the structure and functions of a granum in photosynthesis
. (granum) is formed from many layers of thylakoid membranes to increase surface area (for absorbing light) (1)
. thylakoid membranes contain chlorophyll to absorb light (1)
. electron carrier molecules in thylakoid membrane involved in ATP production
89
Explain how epigenetic changes affect the development of tissues in the embryo.
• DNA (in a chromosome) is wrapped around histones (1)
• {acetylation / modification} of the histone affects {binding of
RNA polymerase / chromosome unwinding} (1)
• methylation of DNA affects { transcription of genes /
production of mRNA } (1)
• therefore gene expression is altered (1)
90
Explain why antibody levels are different in people who have previously had a vaccine when they are exposed to same virus.
Antibodies are present from vaccination
There is a secondary immune response
Memory cells are present from vaccine
Memory cells produce antibodies immediately on exposure to same antigen.
91
Suggest why treatment with antibiotics may not be effective against the dormant bacteria in the tubercles.
Bacteria is inside macrophages
Have waxy coat
Resistant to antibiotics
92
Explain why antibiotics are not used to treat Ebola haemorrhagic fever.
Antibiotics attack organelles in bacteria, so viruses are unaffected.
93
Explain why the evolution of the virus might reduce the effectiveness of any vaccine being developed.
. Vaccine stimulates immune response specific to viral proteins
. Mutations in virus nucleic acid
. Changes shape of viral proteins
. Antibodies can no longer bind to virus.
94
Suggest why using first generation biofuels instead of petrol and diesel could reduce global warming.
. Biofuels are carbon neutral
. CO2 taken up by photosynthesis light independent reaction during production of plants for biofuel
. Burning fossil fuels releases CO2 which is a greenhouse gas.
95
What does it mean if NPP is high?
More carbon is fixed to produce biomass
Higher rate of photosynthesis
More carbon removed by photosynthesis than released by respiration
96
Explain the relationship between GPP and NPP
. NPP = GPP - R
. Energy is lost as heat to provide energy for active transport
. NPP is stored energy for next trophic level
97
Define GPP
Rate of energy converted into biomass in plants
98
Explain how the effects on plant species could affect animal species.
. Reduction of primary consumer
. Results in loss of animals that feed on plants
. Loss of habitat reduces breeding rate
. Loss of shelter - means more food for predators so they increase in size
99
Define biodiversity
Variety of species in an ecosystem
| Variety of alleles in a gene pool
100
Explain how the structure of the aorta relates to its function
. Lots of collagen to withstand high pressure
. Muscle fibres to control blood flow
. Smooth endothelial wall to reduce friction
. Semi lunar valve to prevent backflow
. Wide lumen to accommodate lots of blood flow
101
Some early studies of schizophrenia included identical twins raised in separate families. Explain how the design of these studies allows the influence of environmental factors on development of schizophrenia to be investigated.
Identical twins being raised apart lets environmental factors to be investigated separately from genetic factors
So we can determine amount of relative risk due to genetic factors/ environmental factors
102
Give three similarities between IAA and animal hormones
. Both chemicals
. Both produced in cells
. Both move away from site of production
. Effect may be distant from production site
. Both can control growth
. Both can be involved in gene activation
103
Auxins can be used to kill unwanted plants such as weeds growing in grass.
The auxin stimulate the weeds to grow rapidly.
Suggest an explanation for how auxins stimulate the weeds to grow rapidly but not the grass
. Weeds are more sensitive + take up more auxin
| Auxin causes cell elongation
104
Explain why a myelinated neurone has a higher conduction velocity
Schwann cells cover axon in myelinated neurone
Schwann cells + myelin provide insulation
There is action potential produced at node of Ranvier
There is saltatory conduction as impulse jumps from node to node
105
Describe how a neurotransmitter, such as glutamate, is released from a brain cell.
There is an arrival of action potential
Calcium ion channels in pre synaptic membrane open
Calcium ions enter down concentration gradient
Causes vesicles to fuse with pre synaptic membrane
Release neurotransmitter via exocytosis into synaptic cleft.
106
Give two benefits of habituation
Saves energy
| Allows maximum feeding effort
107
Explain how vesicles are involved in the successful fertilisation of an egg cell by only one sperm.
Cortical granules fuse with egg cell membrane
| And release chemical contents by exocytosis that harden zona pellucida
108
Explain what is meant by no significant difference at the 0.05 probability level for the rate of breakdown of protein.
* there is {more than a 5% likelihood / less than 95% likelihood} (1)
* therefore the rate of protein breakdown is the same {in space as it is on Earth / for groups 1 and 2} (1)
* the calculated value is less than the critical value (at p=0.05) (1)
109
Explain how twin studies could be used to compare the effects of nature and nurture on human development.
. Identical twins are genetically identical as they come from the same zygote
. Phenotypic differences are due to environment
. Non-identical twins are genetically different
. Any phenotypic differences when environment is the same is due to nature (genetics)
110
The gene therapy involved taking bone marrow stem cells from the child to be treated. A virus was then used to transfer DNA with the dominant allele into the. stem cells. These modified stem cells were then injected into this child.
Suggest how these modified stem cells can result in the prevention of MLD.
. Functioning gene is now in cells
. Gene is transcribed and translated
. Normal protein is produced
. Stem cells produce more cells
111
There are some risks associated with somatic gene therapy.
Suggest why the parents of these children gave consent for their children to be involved in the gene therapy treatment for MLD (dangerous disease).
. The risks from gene therapy are very small
. Consequences of disorder are more certain & dangerous than risks from gene therapy
. Consequences of disorder are known but risks of gene therapy are unknown
. Parents will do anything to treat child of disorder
112
Define phenotype
Appearance of an organism due to it's genotype
113
Explain why it is necessary to test for several different recessive alleles in the screening for cystic fibrosis.
. cystic fibrosis results from one of a number of
possible mutations (of this gene) /eq ;
. idea that testing for only one will miss other recessive alleles ;
114
In the risk analysis shown, if neither partner is a carrier then it is considered that the chance of having a child with cystic fibrosis is low. Explain why the probability of having a child with cystic fibrosis is low and not zero.
ref to false negatives / eq ;
2. idea that the screening programme does not
test for all the possible mutations that can cause cystic fibrosis ;
3. idea that a mutation may occur in the formation of the gametes ;
4. idea of mutation in both gametes ;
5. idea that a mutation may occur after fertilisation ;
115
Describe how a fertilised egg can be used as a source of human pluripotent stem cells.
. Fertilised egg grows for a few days
. Until blastocyst forms
. Cells in inner cell mass are pluripotent
116
Explain how cells can become cancerous
Mutation in genes controlling cell division
| Leading to uncontrolled division of cells
117
Define competition
the struggle for resources
118
Explain how biochemical growth signals can stimulate cell growth
- molecules/ growth factors/ hormones bind to receptors on cell surface
- second messenger activated inside cell
- which activate transcription factors
- protein synthesis activated
- gene expression of genes involved in control of cell cycle
119
Suggest how cancer cells might become resistant to chemotherapy drugs
- chemotherapy drugs bind to target proteins in cancer cells to inhibit them
- mutations change tertiary structure in target proteins/ binding sites
- drugs can no longer bind to target proteins and inhibit them
120
Explain how a mutation can yield proteins that are hyperactive
- change in amino acid
- involved in active site of enzyme
- more effective in binding substrate/ catalysing reaction
- increasing activity of protein
121
Suggest why mice might be a good model system to study cancers such as leukemia.
- mice are relatively easy to manipulate genetically
- genome very similar to human genome
- both mice and humans are mammals: physiological processes likely to be conserved / similar
- conclusions in mice valid in humans
122
Describe how cancer-causing mutations in a specific gene could be introduced into bone marrow cells in mice.
- isolate desirable gene with information for protein responsible for specific trait
- introduce a mutation into the gene and amplify gene using PCR
- create recombinant DNA plasmid / viral genome with desirable gene
- use liposomes / virus as vector
- e.g. inject into bone marrow of mice
123
Describe the differences between embryonic and adult stem cells.
adult: cells from umbilical cord or post-birth, multipotent (can give rise to limited number of cell types)
embryonic: cells from blastula stage, pluripotent (can give rise to most cell types)
124
Describe how gene activity can be controlled.
- transcriptional activators / repressors binding to promotor region
- allow / prevent RNA polymerase binding to promotor
- transcription can/ cannot happen
125
Explain how cell division occurs normally in stem cells.
- cell cycle
- G1 and G2 phases: growth / replication of organelles /high metabolic activity
- S phase: DNA replication
- M phase: mitosis (nuclear division) and cytokinesis (cell division)
126
Leukemia is a condition where the bone marrow produces lymphocytes that don't function properly / slow down the production of healthy blood cells. Suggest why people with leukemia are prone to recurrent infections?
- lymphocytes include B cells and T cells
| - important in specific immune response e.g. production of antibodies or cytokines, memory cells
127
Explain the role of inflammation defending the body against infections.
- part of the non-specific immune response
- mast cells release histamines
- vasodilation /increased blood supply increased permeability of capillaries
- white blood cells / neutrophils recruited to destroy bacteria
128
What are hormones?
chemical messengers produced by glands transported in bloodstream to activate target cells
129
Explain why some bacteria do not cause a primary immune response
Some bacteria have mucus coat
Some bacteria are in body cells
Some antibodies are already present from breast feeding
130
Suggest why antibiotics may be used to treat the flu
. Flu may allow development of opportunistic infections
| . Antibiotics kill + prevent growth of bacteria
131
Suggest why effective treatment of HIV in human populations will require the continual development of a mixture of many new drugs.
. HIV has many different strains, each with different antigens
. Some strains become resistant to drugs
. Mixture of drugs has more chance of getting rid of all strains
. There is a rapid rate of mutation
. Rapid rate of multiplication
132
Suggest the advantage of using monoclonal antibodies, rather than polyclonal antibodies, in the detection of antigens in the blood.
. specific antigen identified
. antibody only binds to one antigen
. specific treatment can be given
. more likely to be effective
