2.2. Carbohydrates and lipids
A subsection of Biology, 9700, through 2. Biological molecules
Listing 10 of 368 questions
Saccharomyces cerevisiae is a unicellular fungus that is important in the brewing and baking industries. is a diagram of a transmission electron micrograph of S. cerevisiae. lysosome vacuole lipid droplet nucleus 1 μm cell surface membrane glycogen granule cell wall A student was asked to calculate the magnification of the image shown in . The student began by measuring the length of the scale bar in millimetres using a millimetre ruler. State what the student should do next to obtain the correct answer. One function of the lipid droplets shown in is to store triglycerides. The triglycerides in a lipid droplet are surrounded by a single layer of phospholipids. Suggest and explain why phospholipids, rather than triglycerides, are used for the outer monolayer of the lipid droplet. The lysosomes and vacuole of S. cerevisiae contain acid hydrolases (hydrolytic enzymes) that function in an acid pH. Explain why lysosomes need hydrolases to carry out their function. A disaccharide, trehalose, is a reserve store of energy for S. cerevisiae when glycogen stores decrease. The monomer of glycogen and trehalose is α-glucose. Complete to show the ring structure of one α-glucose molecule. CH2 H OH O OH H H A student carried out tests on a solution of trehalose and correctly concluded that trehalose is a non-reducing sugar. Outline the procedure carried out by the student and state the results that were obtained. The hydrolysis of trehalose is catalysed by two different enzymes produced by S. cerevisiae, regulatory trehalase and non‑regulatory trehalase. A study was carried out to compare regulatory trehalase and non‑regulatory trehalase extracted from S. cerevisiae. The results of the study showed that: • regulatory trehalase had a higher Km value (Michaelis‑Menten constant) than non‑regulatory trehalase • the optimum pH of regulatory trehalase was pH 7.0–7.8 • the optimum pH of non‑regulatory trehalase was pH 4.5–5.0. Explain what is meant by a higher Km value. Regulatory trehalase is found only in the cytosol, the fluid part of the cytoplasm. Non‑regulatory trehalase has been found on the external surface of the cell surface membrane and inside the cell. State the location inside the cell where non‑regulatory trehalase is likely to be found and explain the reason for your answer. Explain whether both types of trehalase, regulatory and non‑regulatory, can be described as intracellular enzymes. Saccharomyces boulardii is a strain of S. cerevisiae. It has been researched for its possible health benefits for some gut diseases. Researchers investigating trehalase extracted from S. boulardii concluded that only one type of trehalase was present in the extract. shows the effect of pH on the activity of the trehalase extracted from S. boulardii. trehalase activity / arbitrary units pH With reference to and to the two different types of trehalase enzyme produced by S. cerevisiae, state and explain what can be deduced about the type of trehalase present in S. boulardii.
9700_s20_qp_23
THEORY
2020
Paper 2, Variant 3
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Questions Discovered
368