8.4

Translocation

Cambridge IGCSE Biology (0610)  · Unit 8: Transport in plants  · 10 flashcards

Translocation is topic 8.4 in the Cambridge IGCSE Biology (0610) syllabus , positioned in Unit 8 — Transport in plants , alongside Xylem and phloem, Water uptake and Transpiration.  In one line: Translocation is the movement of sucrose and amino acids within the phloem, from sources (where they are produced) to sinks (where they are used or stored).

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).  It is a Supplement (Extended-tier) topic, so it appears only on the Extended-tier papers.

The deck below contains 10 flashcards — 3 definitions, 3 key concepts, 2 process cards, 1 application card and 1 identification card — covering the precise wording mark schemes reward.  Use the 3 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

Translocation in plants

Translocation is the movement of sucrose and amino acids within the phloem, from sources (where they are produced) to sinks (where they are used or stored).

Example: Sucrose produced in leaves is transported to growing roots or developing fruits.

What the Cambridge 0610 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Describe Describe translocation as the movement of sucrose and amino acids in phloem from sources to sinks Supplement
  2. Describe Describe: (a) sources as the parts of plants that release sucrose or amino acids (b) sinks as the parts of plants that use or store sucrose or amino acids Supplement
  3. Explain Explain why some parts of a plant may act as a source and a sink at different times Supplement
Definition Flip

What is translocation in plants?

Answer Flip

Translocation is the movement of sucrose and amino acids within the phloem, from sources (where they are produced) to sinks (where they are used or stored).

Example: Sucrose produced in leaves is transported to growing roots or developing fruits.
Definition Flip

Define 'source' in the context of translocation.

Answer Flip

A 'source' is any part of a plant that releases sucrose or amino acids into the phloem for translocation.

Example: Mature leaves are sources during photosynthesis, exporting sucrose to other plant parts.
Definition Flip

Define 'sink' in the context of translocation.

Answer Flip

A 'sink' is any part of a plant that uses or stores sucrose or amino acids, receiving them from the phloem.

Example: Growing roots, developing fruits, and storage organs like potato tubers are sinks.
Key Concept Flip

Explain why a plant part can act as both a source and a sink at different times.

Answer Flip

A plant part's role can change depending on its developmental stage and the plant's needs.

Example: A developing leaf acts as a sink, importing sucrose, but later becomes a source as it photosynthesizes and exports sucrose.
Key Concept Flip

What substances are transported during translocation?

Answer Flip

The main substances transported during translocation are sucrose (a type of sugar) and amino acids. These are organic compounds vital for plant growth, respiration, and protein synthesis.

Example: These nutrients support growth of new shoots during spring.
Key Concept Flip

In what plant tissue does translocation occur?

Answer Flip

Translocation occurs specifically in the phloem tissue. The phloem consists of sieve tube elements and companion cells, which facilitate the transport of sugars and amino acids.

Example: Aphids feed on phloem sap due to its high sucrose content.
Key Concept Flip

What is the main form of sugar transported during translocation?

Answer Flip

Sucrose is the primary sugar transported during translocation. It's a non-reducing sugar, making it less reactive and thus suitable for long-distance transport within the plant.

Example: Sucrose is converted to starch for storage in potato tubers.
Key Concept Flip

Give an example of a storage organ acting as a sink and then a source.

Answer Flip

Potato tubers act as a sink, storing starch (converted from sucrose) during the growing season. In spring, the tuber becomes a source, converting starch back to sucrose to support new shoot growth.

Example: New potatoes are harvested during summer.
Key Concept Flip

Describe how sucrose is loaded into the phloem at the source.

Answer Flip

Sucrose is actively transported into the companion cells and then into the sieve tube elements of the phloem. This process requires energy (ATP) to maintain a high sucrose concentration in the phloem.

Example: Proton pumps maintain a gradient that facilitates sucrose entry.
Key Concept Flip

Describe how sucrose is unloaded from the phloem at the sink.

Answer Flip

Sucrose is unloaded at the sink cells, either passively (following a concentration gradient) or actively (requiring energy). Once unloaded, sucrose is either used for respiration, growth, or converted to starch for storage.

Example: Root cells use sucrose for respiration to uptake mineral ions from soil.

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8.3 Transpiration 9.1 Circulatory systems

Key Questions: Translocation

What is translocation in plants?

Translocation is the movement of sucrose and amino acids within the phloem, from sources (where they are produced) to sinks (where they are used or stored).

Example: Sucrose produced in leaves is transported to growing roots or developing fruits.
Define 'source' in the context of translocation.

A 'source' is any part of a plant that releases sucrose or amino acids into the phloem for translocation.

Example: Mature leaves are sources during photosynthesis, exporting sucrose to other plant parts.
Define 'sink' in the context of translocation.

A 'sink' is any part of a plant that uses or stores sucrose or amino acids, receiving them from the phloem.

Example: Growing roots, developing fruits, and storage organs like potato tubers are sinks.

More topics in Unit 8 — Transport in plants

Translocation sits alongside these Biology decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

8.1 Xylem and phloem

15 flashcards
8.2 Water uptake

8 flashcards
8.3 Transpiration

11 flashcards

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0610 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

translocation phloem sucrose amino acid source sink sieve tube companion cell active process

Key terms covered in this Translocation deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

Translocation in plants
'source' in the context of translocation
'sink' in the context of translocation

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How to study this Translocation deck

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