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

Last question. Microscope topic is in unit 1. So I thought it made more sense to talk about speciation and evolution because that whole section was about biodiversity.

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Last question. Microscope topic is in unit 1. So I thought it made more sense to talk about speciation and evolution because that whole section was about biodiversity.

Posted from TSR Mobile

I don't know what people are talking about when they say underlining, has somebody underlined their answer??

Is there an unofficial mark scheme for this? I didn't think it was too bad but a lot of my friends thought it was really hard so hopefully grade boundaries won't be too high

I was sosososo lucky that I looked over it just before entering the exam.
I suspect lots of brain farts tomorrow, in Chemistryy!

What I got.. I've missed a few marks out because I can't think of them

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

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

Why collagen is good for arteries (1)
I put insoluble, there were many others

Describe the structure of collagen molecule (6)
Fibrous
3 polypeptide chains twist to form triple helix
Held by hydrogen bonds
Every third is glycerine making more compact
Covalent bonds between molecules gives strength
Then I referred to primary, secondary and tertiary structure

Q2
Type of biological molecule (1)
Enzyme

Why can it catalyse both (3)
Both have an OH group on the end meaning they have a similar shape to one another, both substrates can bind to the complementary active site of alcohol dehydrogenase and so are able to form ESCORT by induced fit

Why high ethanol concentration decreases toxicity (3)
Ethanol acts as a competitive inhibitor with a similar shape. It forms enzyme inhibitor complexes to the complementary active site. Producing a non toxic product. Low amounts of Ethanol produce ESC which form a toxic product

Q3
Infective agent of TB (1)
Mycobacterium tuberculosis

How its transmitted (2)
Airborne droplet (coughing, sneezing etc), I also mentioned the fact that physical contact could spread it

Describe the data between 2000 and 2008 (3)
I can't remember which but one group remained the same one went up and one went down
(Pretty straightforward)

Why low income have greater incidence (3)
Homelessness
Poor health due to not being able to afford health care
Overcrowding

Q4.
Which cells are phagocytes? (1)
B&C

Why "secondary"? (1)
Because primary defence occurs first (I.e skin). If the pathogen is able to get past this then phagocytes are initiated

Why is it non-specific? (1)
Does not involve B&T lymphocytes to have receptors complementary to certain antigens

What happens after pathogen attaches to phagocyte? (7)
Pathogen attaches to receptors on phagocyte (already stated)
Pathogen engulfs bacteria by phagocytosis
Becomes a phagosome and moves to the lysosomes by the cytoskeleton
Lysosomes engulf the phagosome making it into a phagolysosome
Release lysins which hydrolyse polymers into monomers
Antigens move to the surface of the membrane, cytoplasm absorbs all other products

Q5.

Calculate SI of Diversity (3)
I got 0.633 something like that

Species richness (1)
Number of species present in a habitat (I also put measured using line transect, qualitative and visual observations)

Species evenness (1)
Measures the abundance of individuals in a species (quantitative using quadrants)

Low SI Index (2)
Certain species is dominant, unstable habitat, low frequency of useful alleles

Improve accuracy of sampling (2)
Use a key to identify species
Sample more than one area

Q6.

Question but I'm unsure what is was

Why crop yield varies (2)
Use of fertilisers, different selection pressures, different alleles

How genetic variation arises (1)
Random gene mutation

Selective breeding
I mentioned that the American plants with the resistant allele need to breed
Offspring with desired characteristic are the ones that will breed over generation to pass on their gene
Inbreeding to keep the desired gene in the population
After many generation frequency of alleles resistant will have increased
Long term - I think I mentioned use of fertilisers or pesticides, and also isolating some of the species with different selection pressures so if a new disease was to break out then the whole population would not be affected

Q7.
define biodiversity (2)
Number and variety of species in the world, the genes they carry and the habitats in which they live

Why conservation methods needed for the specific area (2)
Ecotourism
Gene pool/genetic diversity (there were many more)

Suggest why people against culling (1)
Ethically wrong, we have a moral responsibility to conserve biodiversity

Why red squirrel population may be higher than counted (2)
People might not be able to identify red and grey squirrels properly
Not representative as some areas may have more grey squirrels which were counted

EIA criteria (3)
Effects biodiversity
Harm habitats or endangered species
Affect and ecosystem or food chain

Q8.
Draw dotted lines (3 between C&G), (2 between A&T) (2)

Components of DNA (2)
Cytosine
Nucleotide

Complete gaps (2)
Protein? (Might be polypeptide)
Ribosome

How RNA would be different to DNA (2)
RNA is not double stranded
RNA would have uracil

Why it is "semi-conservative" (2)
Old stand and new strand form, template is old strand

Why complementary base-pairing is important (2)
Determines primary structure of protein
Would not form double helix

Draw in the R1 and R2 (2)
I did one intermediate DNA then on the next. Intermediate and light DNA

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

Q9
(5)
genus? (Can't remember)
Can't remember it was class or order
phylum
Kingdom = Animalia
Domain = Eukaroyta

Phylogeny (3)
Study of evolutionary relationships between species, looks at how closely related they are are whether they have common ancestors. Helps taxonomists classify (anatomy, morphology, cytochrome c), also compares there characteristics

Why water bear was undiscovered (2)
Too small to be seen
Technologies were not up to date
(I got this wrong not really sure about it)

This is what I put and by no means am I correct but you can compare. Also see what I would roughly get maybe? As I said it would be a guess because I've missed some marks out

What did everyone write for the question on EIA?
I wrote that they assess:
-Whether the area is habitat to an endangered species
-The rarity of the habitat
-To what extent the new development will affect the biodiversity of the area

How likely is it that I get the 3 marks?

What I got.. I've missed a few marks out because I can't think of them

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

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

Why collagen is good for arteries (1)
I put insoluble, there were many others

Describe the structure of collagen molecule (6)
Fibrous
3 polypeptide chains twist to form triple helix
Held by hydrogen bonds
Every third is glycerine making more compact
Covalent bonds between molecules gives strength
Then I referred to primary, secondary and tertiary structure

Q2
Type of biological molecule (1)
Enzyme

Why can it catalyse both (3)
Both have an OH group on the end meaning they have a similar shape to one another, both substrates can bind to the complementary active site of alcohol dehydrogenase and so are able to form ESC by induced fit

Why high ethanol concentration decreases toxicity (3)
Ethanol acts as a competitive inhibitor with a similar shape. It forms enzyme inhibitor complexes to the complementary active site. Producing a non toxic product. Low amounts of Ethanol produce ESC which form a toxic product

Q3
Infective agent of TB (1)
Mycobacterium tuberculosis

How its transmitted (2)
Airborne droplet (coughing, sneezing etc), I also mentioned the fact that physical contact could spread it

Describe the data between 2000 and 2008 (3)
I can't remember which but one group remained the same one went up and one went down
(Pretty straightforward)

Why low income have greater incidence (3)
Homelessness
Poor health due to not being able to afford health care
Overcrowding

Q4.
Which cells are phagocytes? (1)
B&C

Why "secondary"? (1)
Because primary defence occurs first (I.e skin). If the pathogen is able to get past this then phagocytes are initiated

Why is it non-specific? (1)
Does not involve B&T lymphocytes to have receptors complementary to certain antigens

What happens after pathogen attaches to phagocyte? (7)
Pathogen attaches to receptors on phagocyte (already stated)
Pathogen engulfs bacteria by phagocytosis
Becomes a phagosome and moves to the lysosomes by the cytoskeleton
Lysosomes engulf the phagosome making it into a phagolysosome
Release lysins which hydrolyse polymers into monomers
Antigens move to the surface of the membrane, cytoplasm absorbs all other products

Q5.

Calculate SI of Diversity (3)
I got 0.633 something like that

Species richness (1)
Number of species present in a habitat (I also put measured using line transect, qualitative and visual observations)

Species evenness (1)
Measures the abundance of individuals in a species (quantitative using quadrants)

Low SI Index (2)
Certain species is dominant, unstable habitat, low frequency of useful alleles

Improve accuracy of sampling (2)
Use a key to identify species
Sample more than one area

Q6.

Question but I'm unsure what is was

Why crop yield varies (2)
Use of fertilisers, different selection pressures, different alleles

How genetic variation arises (1)
Random gene mutation

Selective breeding
I mentioned that the American plants with the resistant allele need to breed
Offspring with desired characteristic are the ones that will breed over generation to pass on their gene
Inbreeding to keep the desired gene in the population
After many generation frequency of alleles resistant will have increased
Long term - I think I mentioned use of fertilisers or pesticides, and also isolating some of the species with different selection pressures so if a new disease was to break out then the whole population would not be affected

Q7.
define biodiversity (2)
Number and variety of species in the world, the genes they carry and the habitats in which they live

Why conservation methods needed for the specific area (2)
Ecotourism
Gene pool/genetic diversity (there were many more)

Suggest why people against culling (1)
Ethically wrong, we have a moral responsibility to conserve biodiversity

Why red squirrel population may be higher than counted (2)
People might not be able to identify red and grey squirrels properly
Not representative as some areas may have more grey squirrels which were counted

EIA criteria (3)
Effects biodiversity
Harm habitats or endangered species
Affect and ecosystem or food chain

Q8.
Draw dotted lines (3 between C&G), (2 between A&T) (2)

Components of DNA (2)
Cytosine
Nucleotide

Complete gaps (2)
Protein? (Might be polypeptide)
Ribosome

How RNA would be different to DNA (2)
RNA is not double stranded
RNA would have uracil

Why it is "semi-conservative" (2)
Old stand and new strand form, template is old strand

Why complementary base-pairing is important (2)
Determines primary structure of protein
Would not form double helix

Draw in the R1 and R2 (2)
I did one intermediate DNA then on the next. Intermediate and light DNA

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

Q9
(5)
genus? (Can't remember)
Can't remember it was class or order
phylum
Kingdom = Animalia
Domain = Eukaroyta

Phylogeny (3)
Study of evolutionary relationships between species, looks at how closely related they are are whether they have common ancestors. Helps taxonomists classify (anatomy, morphology, cytochrome c), also compares there characteristics

Why water bear was undiscovered (2)
Too small to be seen
Technologies were not up to date
(I got this wrong not really sure about it)

This is what I put and by no means am I correct but you can compare. Also see what I would roughly get maybe? As I said it would be a guess because I've missed some marks out

Just some quick questions, I'm really nervous so please can you firstly I wrote phagoctyes are non specific because they activate the release of B and T cells which destroy pathogens, they don't do it themselves directly.

Another question, I put protein for the question, the other answer was ribosome. People are saying its polypeptide but I was just wondering?

Also, I put phagoctyes are secondary response - I said about memory cells and faster response with more antibodies produced.

It would make me feel better if someone could confirm the marks for these, just for some peace of mind

thanks

Just some quick questions, I'm really nervous so please can you firstly I wrote phagoctyes are non specific because they activate the release of B and T cells which destroy pathogens, they don't do it themselves directly.

Another question, I put protein for the question, the other answer was ribosome. People are saying its polypeptide but I was just wondering?

Also, I put phagoctyes are secondary response - I said about memory cells and faster response with more antibodies produced.

It would make me feel better if someone could confirm the marks for these, just for some peace of mind

thanks

Hi Ellie, first of all protein and polypeptides are the same thing so you'd get the mark.

Phagocytes are secondary defenses, not in the secondary immune response. So nothing to do with antibodies I'm afraid.

It's non specific as it can act on any antigen as opposed to only one like lymphocytes.

Hope I helped.