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Explain how enzymes work in reactions (3 marks)

Enzymes catalyse reactions by reducing the activation energy required to begin a chemical reaction, without being used up in the reaction. They bind to the active site of a substrate to form an enzyme-substr...
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Answered by Lucy P. • Biology tutor
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Colour blindness is a recessive trait caused by an error in the X chromosome. A couple without color blindness are expecting their second child. Their first child was born colour blind. What is the probability of their second child being colour blind?

Colour blindness is recessive, which implies that the child needs to have both chromosomes carrying the genetic error to be born with this condition. We know this is linked to the sex chromosome X so we will...
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Answered by Sabela R. • Biology tutor
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Name two ways in which meiosis produces genetic variation.

Independent segregation (of homologous chromosomes) Crossing over Random assortment
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Answered by Daisy L. • Biology tutor
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Explain how the body responds to a fall in water potential.

Providing there is a basic understanding of the anatomy and functioning of the kidney, we can start by stating that the homeostatic control of osmoregulation in the blood is achieved by hormone ADH (anti-diu...
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Answered by Alexandra S. • Biology tutor
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Describe how phagocytosis of a virus leads to presentation of its antigens

Firstly, specialised white blood cells, known as macrophages, detect the virus in the blood stream. This is due to the virus releasing chemicals, and in the process of chemotaxis, the macrophage follows this...
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Answered by Jennifer L. • Biology tutor
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