Question 1
(i)What starts depolarisation?[2]
First Box -C Second Box - D
(ii) How can the protein’s presence identify pre/postsynaptic membrane? (2)
If X is present, it's the presynaptic membrane if X is absent, it's the postsynaptic membrane
Unidirectional nerve impulse? Only the pre-synaptic neurone forms the synaptic vesicles
(iii) (this question was asking why the drug binding to the receptor doesn’t cause an action potential itself I think)
Drug binds to dopamine receptors - acts as a competitive inhibitor
Binding to dopamine receptors prevents dopamine from binding, prevents the influx of sodium ions into the post synaptic knob so no depolarisation occurs, threshold potential not reached, therefore no action potential is generated (2)
Question 2
(i) Temperature (too high) denature hydrogen bonds in secondary and tertiary structure,
specific tertiary structure of enzymes change. Body cannot carry out metabolic reactions and respire so organs die, if temperature is too low then too slow rate of enzyme catalysed reactions. (3)
(ii) It was about cooling a person/animal and 4 graphs, one for cooling, one for CO2, one for electrical activity and one for the BAT tem
Increase in detection by receptor + increase in impulses from brain for mini two peak in electrical activity graph
electrical impulse increased and co2 concentration increased, increased heart rate due to increased electrical impulses, heart pumps oxygen around the body for aerobic respiration (hence co2 concentration increased) and heat is a byproduct of respiration, heating up the rats skin. Vasoconstriction of arterioles when skin cooled. (4)
Question 3
Wildebeest + Impala - time spent looking up graph [4]
(i) Standard deviations do not overlap, results significant, representative sample, may be moving head other than to look for predators (find shade maybe) so cannot operationalise the results, only looked at one area, only looked for 75 hours, significant for individual species but not when looking at herbivores as a whole.
(ii) Cost of moving head?(2) - higher energy expenditure so must eat more to carry out growth and reproductive processes. Less energy for growth so may have impaired growth, cannot feed - does not eat enough food. May go hungry, less energy for when predator does arrive to escape from the grasses, where it is camouflaged and so more likely to be detected by predators. more visible to predators? The whole idea was for them to expose a larger surface of their body so they’re more likely to be seen by predators
(iii) Calculation [2 marks]
9 Hours -they observed for 75 hours so you had to find the difference of the two values on the graph (0.12) and multiply by 75
Values were 0.23 and 0.11 so you could have done 0.23x75=17.25 and 0.11x75=8.25 and subtracted
Question 4
Role of ATP in myofibril(2)
ATP binds to myosin head to break actin-myosin cross bridge so myosin head can attach to actin binding site further down the actin filament (recovery stroke)
Hydrolysis of ATP also provides energy for “power stroke” - pulls actin over myosin, sarcomere shortens.
ATP for re-uptake of Ca2+ ions to prevent over
Suggest explanation for these results(2)
(phospho)creatine provides the phosphate to make ATP (in fast-twitch muscles?) so rats without the creatine have a lower force (weaker powerstroke) as they have less ATP to supply muscles (2)
Heterozygous individuals produce similar results to Dominant individuals because must be homozygous recessive to not produce creatine, so individual still produces creatine
NO dominant allele in production of no creatine is expressed, so heterozygous express the dominant allele (2)
Question 5
DNA technology
(i) Restriction endonuclease (1)
(ii) DNA Ligase (1)
(iii) Only produced in the one in the nucleus because this is where transcription occurs, the one put in the cytoplasm did not provide desires gene because transcription cannot occur
(iv) Question about positive feedback
T Helper cells released IRF protein - binded to a gene (acted as transcriptional factor)... somehow caused production of more T Helper cells, hence more IRF proteins would have been released
(v) Why is IFR considered a tumour-suppressor gene?
Slows cell division so cancer cells divide more slowly therefore tumour growth is slower
Kills some cells, so can kill cancer/tumour cells
Why can the insect protein be produced in the plant?
Totipotent cells - insect protein produced (codons are universal?), cell can specialise and differentiate.
DNA is universal and so the same triplets code for the same amino acids in all organisms. Therefore plants are able to produce insect proteins using insect DNA.
Question 6
Other DNA technology section
(i) PCR (1)
What is the type of alteration that removed the spacers (or something):
(ii) Deletion Mutation (1) (Not splicing because it was DNA not mRNA and it was a prokaryote)
(iii) Intron (1)
DNA probe complementary to spacers (white squares), binds to form hydrogen bonds (DNA hybridisation) - fluoresces if complementary (inverse also possible?) (3)
I wrote that there are no DNA Polymerase or enzymes required for DNA replication occurring in the cytoplasm
Why groups of cells with gene in nucleus all had gene, meanwhile groups of cells with gene in cytoplasm only some had the gene?
During interphase of meiosis dna/genes in the nucleus is replicated hence both the daughter cells will contain the gene. Meanwhile when in the cytoplasm it is not replicated one one daughter cell of the two produced during replication will contain the gene
Why is it important to know what is the tuberculosis strand? (2)
So that the public can be vaccinated against the specfic strain which is likely to be spread around as the vaccine
More better informed to what particular treatment to administer, To know what antibiotics to give the person? Perhaps to prevent antibiotic resistance
Question 7
2 ways type 1 can be controlled? (2)
- Insulin injection
- control of diet
- Pancreatic Beta cell transplant
- Exercise
The 2 transcriptional factors:
IFR Proteins and Phosphorylated STAT1 (2)
How does diabetes affect ability to respond to changes in blood pressure? (4)
Mice with diabetes had a weaker response (smaller increase or decrease in heart rate) to a change in blood pressure.
Diabetes affected sensitivity of pressure receptors? Less impulses sent from receptors/sensory neurones to medulla, hence weaker responses carried out by heart in response to change in blood pressure.
Baroreceptor detects low blood pressure
Sends impluses to cardioacceleratory centre in medulla
Sends impulses to SAN via sympathetic to speed up heart rate
High blood pressure meant that the medulla oblongata sends impulses via the parasympathetic to slow down heart rate too
decrease in frequency of nerve impulse to medulla oblongata and SAN hence the weaker negative feedback response when the blood pressure deviates from the normal
Question 8
Why did they make these comparisons? (referring to age/number of relapses/time since diagnosis) (1)
Shows that the groups are representative / to see factors which increase the risk of developing MS? Because some factors eg aging make MS worse, which is a factor they need to consider when looking at results for the drug?
They said the drug was effective at treating MS. Evaluate. (4)
For A and B, 95% confidence limits do not overlap so results significant, For B and C, 95% confidence limits do overlap so no significant difference. 2 year period shows long term effectiveness, may be other factors causing relapse (diet)/ could have had other drugs? The most effective concentration of the drug probably would have been between 7mg and 14mg, since there was little different in results.
Scientists compared all factors (age etc) because they affect ms severity so allows them to see effectiveness of drug
Question 9
Modified human antigen - injected into mice.
Antigen protein on surface, recognised as foreign, auto-immune response carried out so myelin sheath inflames/broken down (damaged) (3)
Cristae lower SA for ETC/for NAD/FAD, less ATP synthase in cristae - less ATP produced so less energy provided to carry out processes -Neuron dies. ATP needed for active transport of ions [2 or 3?]
modified human antigen injected, wbc detect as foreign, increase in amount of antibodies/ b cell complementary to the antigen. modified Human antigen are of similar shape to antigen on mice, therefore antibodies also attach to myelin sheath of mice, cause an immune response attacking the myelin sheath.
Which microscope do you use and why?
Electron microscope (TEM) - higher resolution / shorter wavelength, so cristae can be differentiated (2)
Calculating frequency [3]
- calculate area of lens with MM ruler, count number of abnormal mitochondria divide by total number of mitochondria X 100. OR randomly select different areas of neurone - count abnormal mitochondria in each - repeat and calculate a mean number of abnormal mitochondria (in percentage)
Question 10
A) The control of processes in cells and the importance of these processes.
Menstrual Cycle
Islet of Langerhans
hans cells in controlling BGC
Photosynthesis in leaf cells (controlled by limiting factors?)
Respiration-an enzyme controlled reaction
What about all organelles in cells, bacterial cells plasmids plasmid transmission, things like that also maybe plant cell root pressure etc… Red blood cells haemoglobin?/
B) Importance of ions in biology
(types of ions included in the spec: nitrates, nitrites, ammonium ions, phosphates in the form of Pi for ATP, water molecules forming hydrogen bonds, chloride ions in CF and cholera, potassium ions in action potentials and for ORS, sodium ions etc)
-resting potential
-action potential
-pacinian corpuscle
- muscle contraction
- synapses transmission
- oxidative phosphorylation /photophosphorylation - of H+ in respiration/ photosynthesis
- Fe2+ in Haemoglobin.
- Na+/glucose exchange during digestion.
- Active transport of ions in the roots / xylem
- Cl- ions going into post synapse, inhibitiory synapses causing inhibition of AP
-chloride ions causing genetic diseases (CF) and Pathogenic diseases (Cholera)
PO4(3-) ATP, Nucleic acids, Phospholipids(relation to hydrophobic head)
-Nitrate (NO3-)/ nitrite (NO2-) / ammonium ions (NH4+) nitrogen cycle
- ionic bonding in proteins
-The buffer in the blood with HCO3- to buffer the PH of the blood
- co transport of Na+/glucose
- phosphorus cycle and how phosphates are made
-Chloride ions diffuse through CFTR protein - thinner mucus layer.
-Ions actively transported into Xylem to lower water potential!
- Science content max mark = 14 without own knowledge/just a2 knowledge. 16 with outside knowledge.
- Conclusion/ intro not necessary for 3 quality of communication marks, just paragraphing and good spelling
- Generally need 4 or more topics picked to get into a high marking range. Depth is more important.
- Breadth = 3 marks
- Relevance = 3 marks
- Scientific knowledge = 16