Chemical and Physical Basis of Life — A/L Biology

How do I practise Chemical and Physical Basis of Life?

1 question with a worked solution

1. Which physical property of water is primarily responsible for the upward transport of water in the xylem vessels of tall trees against gravity?
   1. A) Maximum density at 4 °C
   2. B) High cohesive and adhesive forces
   3. C) High latent heat of vaporization
   4. D) High specific heat capacity
   Check my answer

   Correct answer: B) High cohesive and adhesive forces

   Cohesion (hydrogen bonding between water molecules) forms an unbroken water column, while adhesion (attraction to hydrophilic xylem cell walls) prevents meniscus detachment, enabling transpirational pull according to the cohesion-tension theory.

   Show worked solution

   Step 1: Review cohesion-tension theory of sap ascent. Step 2: Cohesion provides tensile strength to water column. Step 3: Adhesion maintains capillary contact with hydrophilic cellulose/lignin walls. Step 4: Combined cohesive-adhesive properties drive xylem transport. Answer: High cohesive and adhesive forces.
   Modelled on: the A/L Biology examination pattern

Get this auto-marked

Next in the syllabus

Where does Chemical and Physical Basis of Life fit in the syllabus?

Year 1 · Term 1