What is the role of ATP in a companion cell when sucrose is loaded into a sieve tube element?

7.2.1 state that some mineral ions and organic compounds can be transported within plants dissolved in water

7.2.2.1 apoplast pathway, including reference to lignin and cellulose

7.2.2.2 symplast pathway, including reference to the endodermis, Casparian strip and suberin

7.2.3 explain that transpiration involves the evaporation of water from the internal surfaces of leaves followed by diffusion of water vapour to the atmosphere

7.2.4 explain how hydrogen bonding of water molecules is involved with movement of water in the xylem by cohesion-tension in transpiration pull and by adhesion to cellulose in cell walls

7.2.5 make annotated drawings of transverse sections of leaves from xerophytic plants to explain how they are adapted to reduce water loss by transpiration

7.2.6 state that assimilates dissolved in water, such as sucrose and amino acids, move from sources to sinks in phloem sieve tubes

7.2.7 explain how companion cells transfer assimilates to phloem sieve tubes, with reference to proton pumps and cotransporter proteins

7.2.8 explain mass flow in phloem sieve tubes down a hydrostatic pressure gradient from source to sink