Students investigated the composition of the cell wall of leaf cells of thale cress, Arabidopsis thaliana. The students began by isolating the cell wall components from the rest of the cell material. The students used enzymes extracted from a fungal pathogen of $$$A$$$. thaliana to hydrolyse the cell wall components to smaller molecules. The students prepared a reaction mixture containing the cell wall components and the enzymes. After 24 hours, they separated and identified the smaller molecules found in the reaction mixture. Four types of molecule were identified: - short chains of $$$\beta$$$-glucose - $$$\beta$$$-glucose - peptides - amino acids Explain the presence of these molecules in the reaction mixture after 24 hours of hydrolysis. ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . .........................................................................................................................................

Biology

IGCSE&ALevel

CAIE

Exam No：9700_w24_qp_23 Year：2024 Question No：4(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:

Solution:

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