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Outline the action of B lymphocytes following initial contact with an antigen or antigen presenting cell. (6 marks)

There are 4 stages to the response of B lymphocytes upon contact with antigens. These are antigen presentation, clonal selection, clonal expansion and differentiation. During antigen presentation the lymphoc...
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Answered by Amy D. • Biology tutor
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Describe the structure of a protein and how it determines its function.

The primary structure of a protein consists of a sequence of amino acids joined together by peptide bonds. This is known as a polypeptide chain, which undergoes the most basic level of folding in the shape o...
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Answered by Khuzaima B. • Biology tutor
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Determine the Michaelis-Menten constant from a graph. Compare the affinities of two enzymes that have different Km values. Explain how a competitive inhibitor works and influence Km and Vmax values.

(a) First of all, we have to determine V max by using the graph provided. Try drawing a straight line parallel to the x-axis that is very close to the graph and almost seems to touch it. This is called an as...
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How do cholinergic synapses communicate with each other (5)

Acetycholine released from presynaptic neurone2) Acetylcholine diffuses down its concentration gradient and attaches to receptors on postsynaptic neurones3) This causes sodium channels to open on the post sy...
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Answered by Mohit V. • Biology tutor
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Measles, mumps and rubella (MMR) are dangerous diseases that can be fatal to children. The MMR vaccine is given to children at a young age to produce antibodies against these diseases. Describe how giving the vaccine leads to the production of antibodies.

The vaccine contains weakened or dead antigens (from MMR). These antigens are displayed on antigen-presenting cells which are detected by a specific helper T cell. This stimulates a specific B cell which div...
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Answered by Gracie B. • Biology tutor
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