Cholera is an illness caused by the bacterium Vibrio cholerae. Its symptoms arise because a toxin made by the bacterium interacts with proteins in the cell surface membranes of epithelial cells in the human intestine. Cholera toxin is a protein made up of two subunits, A and B. Subunit A consists of one polypeptide, whereas subunit B is formed from five identical polypeptides. Fig. 3.1 displays the structure of the cholera toxin.
(a(i))[1]
State the level of structure that appears only in a protein with more than one polypeptide chain.
(a(ii))[1]
Identify the part labelled S.
(b(i))[1]
State the transport process used by the ions in this example.
(b(ii))[3]
Because ions move into the lumen, water passes from the epithelial cells into the lumen. Name the process by which water moves and explain why it enters the lumen.
(c(i))[2]
Describe the mode of transmission of cholera.
(c(ii))[2]
Explain how natural disasters can sometimes cause transmission to a larger number of individuals.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Protein structure is identified as quaternary.” …