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IGCSEBiology
Trial Class

Original practice · 5 questions · 15 marks · about 17 minutes

Phloem and Translocation Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions focus on how phloem transports dissolved sugars and amino acids from sources to sinks within the plant.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 4 Extended 3 marks Difficulty 3/5

    Define translocation and state what substances are transported in the phloem.

    Show model answer and marking guidance
    1. Translocation is the transport of dissolved organic substances (assimilates) in the phloem.
    2. Mainly sucrose (dissolved sugars).
    3. Also amino acids.

  2. Question 2

    Paper 4 Extended 4 marks Difficulty 4/5

    Compare the structure and function of xylem and phloem in a table format, giving two differences for each.

    Show model answer and marking guidance
    1. Xylem: dead cells, no end walls; transports water and mineral ions upward.
    2. Phloem: living cells (sieve tubes with companion cells), has sieve plates at end walls.
    3. Phloem transports sucrose and amino acids in both directions (up and down).
    4. Xylem has lignified walls; phloem does not.

  3. Question 3

    Paper 4 Extended 3 marks Difficulty 3/5

    Explain the terms "source" and "sink" in the context of translocation.

    Show model answer and marking guidance
    1. Source: the part of the plant where sugars are produced or released: e.g. Leaves (photosynthesis) or storage organs releasing stores.
    2. Sink: the part where sugars are used or stored: e.g. Growing roots, fruits, developing seeds.
    3. Sugars move from source to sink through the phloem.

  4. Question 4

    Paper 2 Core 2 marks Difficulty 2/5

    Name the two types of cell found in phloem tissue.

    Show model answer and marking guidance
    1. Sieve tube elements.
    2. Companion cells.

  5. Question 5

    Paper 4 Extended 3 marks Difficulty 4/5

    Explain why translocation is an active process that requires energy, whereas water movement in xylem does not.

    Show model answer and marking guidance
    1. Translocation requires energy from respiration to load sucrose into the phloem at the source.
    2. Companion cells use ATP to actively transport sucrose into the sieve tubes.
    3. Xylem transport is passive: driven by transpiration pull and cohesion of water molecules.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

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