OCR Biology F212 Revision [3rd June 2013] (Now Closed)

There was this one 2 mark question that I just couldn't answer. Something about how the phagocyte gets from the bloodstream to the lymphatic system?
The rest of it was alright.

the the RNA different to DNA could I say ribose sugar and RNA single stranded?

the the RNA different to DNA could I say ribose sugar and RNA single stranded?

Please someone else tell me that they found this quite hard?

Realised I put plasmodium for the TB question which is of course for Malaria, and I got the ethanol and DEG question wrong how could I have not noticed that it was an enzyme? Grrrrrrrr!

Hope everyone else thought it went well


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For the squirrel question about why the number of reported cases isnt the same as how many there are, am I right when I said:
Red squirrels are scared of humans so they hide, therefore people dont see them .
Also, people could be counting/spotting the same grey squirrels repeatedly.

For the squirrel question about why the number of reported cases isnt the same as how many there are, am I right when I said:
Red squirrels are scared of humans so they hide, therefore people dont see them .
Also, people could be counting/spotting the same grey squirrels repeatedly.

Histamine. Apparently it makes the capillaries more leaky and fluid passes into the lymphatic system or something like that. I wrote that. :/

Whats the answer for "Why are phagocytes in the tissue fluid?"
I wrote that they have a multi-lobed nucleus which allows them to squeeze through the gaps in capillary walls.

What would 69/100 be? This is me being a generous marker :P


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What would 69/100 be? This is me being a generous marker :P


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For drawing the lines for r1 and r2 I got them in the right position but for r2 I didn't have the lines half as thick, think that would matter?


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What would 69/100 be? This is me being a generous marker :P


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I got almost all Same answers as the unofficial mark scheme. But you missed the question how phagocytes enter tissue fluid? I wrote that infected cells release histamine. This chemical makes capillaries more leaky so blood comes out forming tissue fluid and blood carries with it phagocytes.

So here's my interpretation of the paper for anyone who wants to read (maybe TLDR :P)

Q1
Name given to sequence of amino acids (1)
I put primary structure

Draw the structure of an amino acid (3)
H2NCRHCOOH (drawn out)

Why collagen is good for arteries (1)
I put strong/tough to withstand high blood pressure, but i'm uncertain, flexibility probably would have been better.

Describe the structure of collagen molecule (6)
3 coiled polypeptide chains (quarternary structure) to form a rope
Left hand helix shape
Glycine is 1 in every 3 amino acids (smallest R group, close packing)
Hydrogen bonds between polypeptides
(now I'm not sure the next is right as it says the collagen molecule but I mentioned lysine's and covalent cross links
I also said insoluble but I'm not sure thats part of structure,

Q2
Type of biological molecule (1)
Enzyme

Why can it catalyse both (3)
I talked about enzyme active site specificity complimentary to substrate. Both molecules have similar shapes/bonds, basically same except 2 less Hydrogen and 1 Oxygen in the DHP (or w/e it was called) So ESC forms.

Why high ethanol concentration decreases toxicity (3)
I said they both compete for the active site, where ethanol is present it will enter and stop DHP from entering. So less DHP can be broken down in the same amount of time, so toxic products formed slower, so body can remove these before concentration increases too much.

Q3
Infective agent of TB (1)
Mycobacterium tuberculosis

How its transmitted (2)
Exhaled droplets of moisture by infected person inhaled by uninfected people, through coughing, sneezing, laughing, talking (I think you could also mention cattle meat for M.Bovis)

Describe the data between 2000 and 2008 (3)
I said low income and middle low stay the same (figures)
Medium upper increases I think it was and upper decreases
Both years low is highest incidence, upper is lowest incidence]

Why low income have greater incidence (3)
More likely to have malnutrition
Unable to afford vaccines/antibiotics or take antibiotics when needed
Overcrowding and sleeping as cannot afford to buy separate houses

Q4.
Which cells are phagocytes? (1)
I put just C although apparently B is too but it looks just as similar to a lymphocyte and a monocyte in my opinion so there should hopefully be allowance in the MS.

Why "secondary"? (1)
After primary defence breached, part of immune response to antigens

Why "non-specific"? (1)
Can attach to any foreign antigens

What happens after pathogen attaches to phagocyte? (7)
Engulfed, membrane infolds, phagocytosis, endocytosis
Phagosome formed
Lysosomes move towards and fuse with phagosome
secrete hydrolytic enzymens/lysins
break down/digest pathogen
Into soluble products (e.g. amino acids)
absorbed into cytoplasm
waste excreted
macrophages can become APC's

Q5.

Calculate SI of Diversity (3)
I got 0.6 something

Species richness (1)
Number of species present in an area

Species evenness (1)
Relative numbers of individuals of each species present in an area

Low SI Index (2)
Low biodiversity suggests dominated by few species
If environmental change, habitat cannot adapt, dependence on that species

Improve accuracy of sampling (2)
use random sampling, random coordinates generated by calculator
Repeat at different times of month/year (I was thinking about selecting suitable quadrate size but chose the other)

Q6.
There's a 1 mark question here I can't quite remember, something about genetic variation I think (1)

Why crop yield varies (2)
I put insecticides used to stop disease spread, resistance to insecticides, use of fertilisers, climate change (temp/rainfall)

How genetic variation arises (1)
Mutation (i wondered if you could put sexual reproduction also)

Selective breeding short term + long term (7)
I said this is artificial selection
Select wild varieties with resistance and cross breed
prevent asexual reproduction
Select offspring with resistance and highest yield
Cross breed again
repeated for many generations - this is all short term
Then long term - mutations can cause pathogens to change
Conserve wild plants, botanic gardens, seed banks, potential of alleles to other diseases
Multiple alleles to provide better protection
I also mentioned gene marking somewhere

I have to admit this question threw me a bit though

Q7.
define biodiversity (2)
Variety of life, range of living species, habitats and communities and the ecosystems of which they form a part
Genetic variation within and between species

Why conservation methods needed for the specific area (2)
Important part of food chains
Tourism, aesthetically pleasing ( I wonder if you could also put gene pool etc.)

Suggest why people against culling (1)
I said morally wrong, inhumane to trap and kill just to keep population down

Why red squirrel population may be higher than counted (2)
Grey squirrels not intimidated by humans, red hiding, not seen
red have better camouflage for red trees, not seen (not sure this is right)

EIA criteria (3) (did not like this one)
Effect on biodiversity, environmental sensitivity due to noise pollution (wind turbines)
whether there are any endangered species (e.g. red squirrel)
Method to reduce impact (e.g. translocation of red squirrels)

Q8.
Components of DNA (2)
Nitrogenous organic base (I put cytosine as well because it was next to G)
Nucleotide

Complete gaps (2)
Polypeptide
Ribosome

How RNA would be different to DNA (2)
RNA would be single stranded
RNA would have U instead of T

Why it is "semi-conservative" (2)
2 DNA molecules produced, each has one old strand and 1 new strand forms by new nucleotides.

Why complementary base-pairing is important (2)
identical molecules of DNA are produced
so exact protein is made
purine to pyramidine
Different base would be mutation, different protein

Draw in the R1 and R2 (2)
For R1 I did a line between the N15 line and the N14 line
For R2 I did half a line at the same position as R1 and the other half at N14

3 precaution in centrifugation (3)
Same concentration of sugar solution
Same volume of sugar solution
Same time for centrifugation

Q9
Fill space (5)
Whatever the genus was
I think I got order
I think I got phylum
Kingdom = Animalia
Domain = Eukaroyta

Phylogeny (3)
Study of evolutionary relationships, involves ancestral trees
Classification, placing organisms in groups based on similarities (biochem/anatomy)
Phlyogeny shows how recent is the common ancestor, more recent = more similarities
therefore organism placed in similar groups
less time for mutation/variations to arise

Why water bear was undiscovered (2)
Too small to be seen
Microscopes were not available
Also talked about speciation because it did say
why were they not discovered "before 300 years" I think.

Anyway, these are may answers, they may not necessarily be correct, just for people to make comparisons.