Who this is for: Cambridge IGCSE Biology (0610) students who want translocation — movement of assimilates in phloem from source to sink — to become a reliable source of marks instead of a process confused with transpiration or xylem transport.
What query it owns: how to understand and revise translocation in Cambridge IGCSE Biology (0610).
Why this is safe: this page owns the translocation revision-guide angle, while Tutopiya’s Translocation subtopic page owns the learning resource and the free Translocation quiz owns the practice.

Translocation is one of the most frequently tested processes in the Transport in Plants unit of Cambridge IGCSE Biology (0610). Whenever a question involves sucrose moving from leaves to roots, phloem structure, or the terms source and sink — examiners expect a precise definition and a clear contrast with xylem transport. This guide explains exactly what translocation covers, how to handle the question types that actually appear, and where to practise each skill.

Key takeaways

• Translocation is the transport of assimilates (mainly sucrose and amino acids) in phloem from a source to a sink.
• A source produces or releases assimilates (e.g. green leaves in photosynthesis); a sink uses or stores them (e.g. roots, fruits, growing tips).
• Transport is up and down the plant — unlike xylem, which mainly moves water upward.
• Companion cells provide energy for loading sucrose into sieve tubes.
• Always separate translocation from transpiration (water vapour loss) and xylem transport (water and minerals).

What is translocation in Cambridge IGCSE Biology?

Translocation is the movement of organic substances — primarily sucrose and amino acids — through the phloem from regions where they are made or released (sources) to regions where they are used or stored (sinks). In Cambridge IGCSE Biology (0610) the classic example is sucrose produced in photosynthesising leaves transported to root cells for respiration or to fruits for storage. The process requires living phloem tissue and energy from companion cells.

You can read the full explanation, diagrams and notes on Tutopiya’s Translocation subtopic page before you attempt questions.

The core ideas you must master

Idea	What it means	How the exam uses it
Assimilates	Products of photosynthesis — mainly sucrose	”State what is translocated in phloem.”
Source	Makes/releases assimilates	”Identify the source in a growing plant.”
Sink	Uses/stores assimilates	”Name a sink tissue.”
Phloem structure	Sieve tubes + companion cells	”Explain the role of companion cells.”
Direction	Up and down	”Compare xylem and phloem transport.”

Source and sink: examples for exams

Part of plant	Often acts as	Reason
Mature green leaf	Source	Photosynthesis produces sucrose
Growing root tip	Sink	Needs sucrose for respiration and growth
Developing fruit	Sink	Stores sucrose
Storage root (e.g. carrot)	Sink (then source in spring)	Stores assimilates
Apical bud	Sink	Active growth needs sugars

Note: a organ can change — a storage root is a sink in summer but may become a source when shoots grow in spring.

How to answer translocation questions — step by step

1. Define translocation — transport of assimilates (sucrose/amino acids) in phloem.
2. Name source and sink for the scenario in the stem.
3. State direction — up and down, unlike xylem.
4. Mention phloem — sieve tubes, companion cells, living tissue.
5. For compare questions — contrast substance, direction, dead vs living tissue with xylem.
6. Check you have not described transpiration — water vapour from leaves is a different process.

Test yourself with the free Translocation quiz after working through define and compare stems.

Translocation in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical translocation stem
Define	Precise meaning	”Define translocation.”
State	Short factual answer	”State what is transported in phloem.”
Explain	Mechanism or role	”Explain why companion cells are needed.”
Suggest	Apply to context	”Suggest the sink in a plant with developing fruits.”
Compare	Differences	”Compare transpiration and translocation.”

Worked exam-style stems (how to answer the wording)

1. “Define translocation.” Transport of assimilates / sucrose / organic substances in phloem from source to sink. Mark-scheme reward: assimilates/sucrose + phloem + source to sink.
2. “A plant has large fruits and few leaves. Suggest which part is the source and which is the sink.” Source: remaining leaves (photosynthesis). Sink: fruits (store sucrose for growth). Reward: correct identification with reason.
3. “Compare the transport of water and the transport of sucrose in a plant.” Water: xylem, upward, transpiration pull, dead vessels. Sucrose: phloem, up and down, translocation, living sieve tubes. Reward: tissue + substance + direction for both.

When you can recognise the wording instantly, work the full set on the Transport in Plants topical past paper questions and the Translocation quiz.

How translocation connects to the rest of Biology (0610)

Translocation links photosynthesis (sucrose source in leaves) to respiration and growth in sinks. It depends on phloem structure from Xylem and Phloem and contrasts with transpiration and water uptake. When you are ready to mix topics, the Cambridge IGCSE Biology resource hub links every Transport in Plants resource.

Common mistakes students make

• Confusing translocation with transpiration — similar names, different substances and tissues.
• Saying phloem transports water — water is in xylem.
• Stating transport is only upward in phloem — it moves from source to sink in any direction.
• Forgetting companion cells when explaining energy for loading.
• Naming stem as source without checking if leaves are present in the scenario.

When you need more support

If translocation questions keep tripping you up — especially source/sink scenarios or compare questions with xylem — work through the Transport topical past paper questions and the Translocation quiz, then get focused help from a Cambridge IGCSE Biology tutor.

Frequently asked questions

Is translocation hard in Cambridge IGCSE Biology? The core ideas are manageable. Marks are lost when students confuse translocation with transpiration or omit source and sink.

What is the quickest way to define translocation in an exam? Transport of assimilates (sucrose) in phloem from source to sink.

Can the direction of translocation change? Yes — transport follows source to sink; a storage organ can switch between sink and source seasonally.

How do I revise translocation effectively? Read the subtopic notes, practise source/sink scenarios, compare with xylem, then take the Translocation quiz.

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