Yeast cells contain enzymes that catalyse the breakdown of sugars, such as glucose and sucrose, to produce ethanol and carbon dioxide. As the sugars are broken down, the yeast cells in a suspension will sink slowly to the bottom of the container, forming a sediment with a clear liquid above. This process is called sedimentation. You will investigate the effect of different concentrations of ethanol on the sedimentation of yeast cells. In fermentation, the action of yeast converts some of the carbohydrates in plants to ethanol and carbon dioxide. A scientist investigated the production of ethanol during the fermentation of carbohydrates from different sources. The investigation was carried out at $$$30^{\circ} \mathrm{C}$$$ and at pH 5 , using the yeast Saccharomyces cerevisiae. All other variables were kept constant. The results are shown in Table 1.4. (i) Draw a bar chart of the data in Table 1.4 on the grid in Fig. 1.2. Use a sharp pencil. The investigation was repeated using a different yeast, Schizosaccharomyces pombe. All the variables were kept the same as in the first investigation. The percentage of ethanol produced using Schizosaccharomyces pombe was found to be lower with all of the sources of carbohydrate. The results are shown in Table 1.5. (ii) Suggest why the percentage of ethanol produced by Schizosaccharomyces pombe is lower than the percentage of ethanol produced by Saccharomyces cerevisiae for all sources of carbohydrate. ....................................................................................................................................... . ....................................................................................................................................... . .................................................................................................................................

Biology

IGCSE&ALevel

CAIE

Exam No：9700_s24_qp_33 Year：2024 Question No：1(b)

Answer:

Knowledge points:

2.2.1 describe the ring forms of α-glucose and β-glucose

2.2.10 relate the molecular structure of triglycerides to their functions in living organisms

2.2.11 describe the molecular structure of phospholipids with reference to their hydrophilic (polar) phosphate heads and hydrophobic (non-polar) fatty acid tails

2.2.2 define the terms monomer, polymer, macromolecule, monosaccharide, disaccharide and polysaccharide

2.2.3 describe the formation of a glycosidic bond by condensation, with reference both to polysaccharides and to disaccharides, including sucrose

2.2.4 state that glucose, fructose and maltose are reducing sugars and that sucrose is a non-reducing sugar

2.2.5 describe the formation of a glycosidic bond by condensation, with reference to disaccharides, including sucrose, and polysaccharides

2.2.6 describe the breakage of a glycosidic bond in polysaccharides and disaccharides by hydrolysis, with reference to the non-reducing sugar test

2.2.7 describe the molecular structure of the polysaccharides starch (amylose and amylopectin) and glycogen and relate their structures to their functions in living organisms

2.2.8 describe the molecular structure of the polysaccharide cellulose and outline how the arrangement of cellulose molecules contributes to the function of plant cell walls

2.2.9 state that triglycerides are non-polar hydrophobic molecules and describe the molecular structure of triglycerides with reference to fatty acids (saturated and unsaturated), glycerol and the formation of ester bonds

Answer:

Knowledge points:

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