Exams Questions

Outline the roles of the cell surface membrane:

• Protects the organelles from damage.

• Cell signalling

• Cell recognition

• Controls which substances can enter or leave the cell.

• Site of catalysing reaction

How sucrose in the phloem sieve tubes reaches the sink from companion cell.?

1 mass flow

2 (entry of sucrose) decreases water potential in sieve tube ; A  for water potential

3 water enters (sieve tubes), down water potential gradient / by osmosis ;

4 increase in volume ;

5 increase in / high(er), hydrostatic pressure

6 unloading / removal, of sucrose and water at sink lowers hydrostatic pressure

7 movement (from source to sink) is down (hydrostatic) pressure gradient ;