The cholera bacterium releases a protein toxin called choleragen. The toxin causes the loss of chloride ions and water from epithelial cells into the lumen of the intestine. Fig. 6.1 shows the events that occur in cells lining the intestine when choleragen binds to the membrane of one of these cells. Fig. 6.1 (i) State one likely source of an outbreak of cholera. ................................................................................................................................. (ii) With reference to Fig. 6.1, state why choleragen molecules are described as having quaternary structure. ................................................................................................................................. (iii) State the type of cell membrane component that forms the receptor for choleragen. ................................................................................................................................. (iv) The process by which chloride ions leave the epithelial cell requires energy. Name the phosphorylated nucleotide that is needed for this process. ................................................................................................................................. (v) Explain why water also moves from epithelial cells into the lumen of the intestine when choleragen is present. ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . .................................................................................................................................

Biology

IGCSE&ALevel

CAIE

Exam No：9700_w24_qp_23 Year：2024 Question No：6(b)

Answer:

Knowledge points:

10.1.1 state that infectious diseases are caused by pathogens and are transmissible

10.1.2.1 cholera – caused by the bacterium Vibrio cholerae

10.1.2.2 malaria – caused by the protoctists Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale and Plasmodium vivax

10.1.2.3 tuberculosis (TB) – caused by the bacteria Mycobacterium tuberculosis and Mycobacterium bovis

10.1.2.4 HIV/AIDS – caused by the human immunodeficiency virus (HIV)

10.1.3 explain how cholera, malaria, TB and HIV are transmitted

10.1.4 discuss the biological, social and economic factors that need to be considered in the prevention and control of cholera, malaria, TB and HIV (details of the life cycle of the malarial parasite are not expected)

Answer:

Knowledge points:

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