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Biology

A Level

When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how. (5 marks)

With these 5 and 6 mark questions, one of the main skills required is being able to describe the process in sufficient detail, without wasting time with unnecessary information. For example in this questi...

Answered by Thomas R. • Biology tutor

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How do we control the concentration of urine?

Osmoregulation is the homeostasis of water in the body. It is important that water volumes are kept relatively constant as this influences electrolyte concentrations and cell activity.

Answered by Adam B. • Biology tutor

2846 Views

What does the term "Semi-conservative" mean in relation to DNA?

DNA is a double stranded helix. During DNA replication, the strands are separated from each other (using an enzyme called DNA helicase). The unzipped DNA strands then utilize another enzyme, known as DNA ...

Answered by Catherine A. • Biology tutor

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Explain the role of T-cells in immune response to viral infection

When T cells bind to viral antigens presented by macrophages they undergo mitosis to form 4 distinct cell variants:
Memory T cells- remain in the blood stream to initiate a faster immune response upo...

Answered by Will S. • Biology tutor

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Explain how FHS and oestrogen illustrate the principle of negative feedback during the menstrual cycle, and explain therefore why oestrogen may be used as a contraceptive.

FHS is released from the anterior pituitary gland in the brain and causes the follicle to develop in the ovary. the developing follicle produces and secretes oestrogen. This release of oestrogen stimulate...

Answered by Catrin P. • Biology tutor

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