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

Thank you!
Have you done a past paper before!?


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That's so helpful, thanks


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Someone please help me understand what T and B lympcytes are/do and what's the difference between them?

Anyone up for revision !


Lets do immunity ,


Describe the role of antibodies and describe the structure using the words heavy chain and light chain (6 marks)

What's the difference between amylose, amylopectin and starch? Are they all types of starch or is starch made up of amylose and amylopectin molecules? The book's really confusing :/

Antibodies have 4 polypeptide chains, 2 light chains and 2 heavy chains.
They are held together by disulfide bonds.
The hinge region allows flexibility.
The constant region is the same for all antibodies and allows for the antibodies to attach to phagocytes, during phagocytosis,
The variable region is complementary shaped to a specific antigen, it allows the antibody to attach to an antigen.
There are more than one variable regions, which means that the antibody can neutralise more than one antigen at a time.
Antibodies can agglutinate pathogens, this clumps them together making them too large to enter host cells as well as more easily identifiable by macrophages.
They can also neutralise pathogens, by blocking their antigens, preventing them from entering host cells.

Anyone up for revision !


Lets do immunity ,


Describe the role of antibodies and describe the structure using the words heavy chain and light chain (6 marks)

6 marks, excellent work Gotzz

can you ask me please

Describe the differences between the primary and secondary response (4)

Antibodies are produced by Plama Cells, when an Antibody comes in contact with an Antigen it forms an Antigen-Antibody complex. Antibodies contain 2 Heavy Polypeptide chains at the base of the Antibody and 2 Light Polypeptide Chains at the top of the Antibody

Many disulphides bridges form on the Polypeptide chains to prevent the chains from breaking apart

The Antibody has a Variable Region which is different for all Antibodies, this is where an Antigen with a Complementary shape attaches

The Antibody also has a Constant Region which is the same in all Antibodies which is where Phagocytes will bind

The Hinge Region between the Heavy and Light Polypeptide Chains allows flexibility of the Antibody
Roles:
Agglucination of Pathogens, basically more pathogens are phagocytosis due to the Antibody containing 2 Binding sites
Neutralise Toxins, can't bind to toxins basically

Describe the differences between the primary and secondary response (4)

Primary response is where the concentration of antibody is much less and in secondary response the concentration of antibody is much more and takes place usually around day 31. The reason for the natibody production being less in primary response is because if an pathogen enters the host cell and is foreign to the body (Cells) then the lymphocytes have to be activated in which the cytokines that are the second messengers have to bind to the cell surface receptor of the lymphocyte in order to activate a specific lymphocyte which could either be T or B. Then the lymphocyte have to under go clonal selection and expanssion in which it takes time for them to divide by mitosis and once they divide they can differentiate to specific cell types making antibodies( B lymphocyte--> plasma celll--> memory cell--> antibody) for example which remain in the blood/body to provide long term immunological memory and this arises to give the secondary response.

You could also mention that the delay time, before the concentration of antibodies begins to increase, is much quicker in the secondary response.
But good answer, the main points to make are secondary:
More antibodies produced
Antibodies produced at a faster rate
Shorter delay time
ETA: oh and mention the symptoms (none occur during secondary)