Sucrose is a disaccharide. Fig. 2.1 shows how sucrose is broken down in a reaction with hydrochloric acid. [Figure 2.1]

Mark scheme

Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.

1. [2] A - (α-) glucose ; R any qualification of glucose other than a, e.g. ẞ-glucose B - fructose; I hexose sugar I any qualification of fructose, e.g. a
2. [1] glycosidic; R glucosidic I any qualification of glycosidic, e.g. 1–2, 1–6
3. [1] hydrolysis; A acid hydrolysis
4. [2] two from: sucrose is, a non-reducing sugar/non-reducing / not a reducing sugar; A no reducing sugars present no (hydrochloric) acid used (to break down sucrose to reducing sugars); A sucrose not hydrolysed (to monomers / monosaccharides / reducing sugars) (sucrose will not reduce) (blue) copper II ions to (red) copper I ions cannot donate electrons AVP; idea that reactive groups are not available (to react with Benedict's solution / copper ions) no (free), aldehyde / ketone, group
5. [4] hydrostatic required once only in the answers four from: 1 diffusion, into phloem sieve tube (element), from companion cell (through plasmodesmata) ; 2 presence of sucrose (in phloem sieve tube element), lowers water potential / makes water potential more negative ; R if in context of xylem vessels or companion cells 3 water enters (sieve tubes), by osmosis / down water potential gradient (into sieve tubes) ; 4 increase in, hydrostatic, pressure (in sieve tube elements); A turgor pressure 5 low hydrostatic pressure in, storage tissues / root / sink, by removal of sucrose ; 6 movement of, (phloem) sap / sucrose (in solution), down hydrostatic pressure gradient / from high to low hydrostatic pressure; 7 mass flow;