Absorption — Science definition

Defined in 2 courses:

The movement of small food molecules out of the gut and into the blood, mostly across the lining of the small intestine. (Life Science & Scientific Inquiry)
Light energy being taken in by a material, often becoming thermal energy. (Physical Science: Matter, Forces & Energy)

Where it is taught

Digestion, Absorption & Food Molecules — Body Organization, Transport & Movement, Life Science & Scientific Inquiry, Grade 7
Light & the Electromagnetic Spectrum — Waves, Sound & Light, Physical Science: Matter, Forces & Energy, Grade 8

In use

Absorption is the movement of those small molecules out of the gut and into the blood, and it happens mostly in the small intestine, which is built for nothing else.
Digestion, Absorption & Food Molecules

Questions using absorption

Problem 1

How does more exchange area help the absorption model?

Answer and explanation

It provides more surface across which materials can move under suitable conditions, rather than making food molecules appear from nothing.

Problem 2

Illustrative comparison: Sample A remains in one large piece; equal-mass Sample B is divided into small pieces. Both experience the same stated enzyme conditions; B breaks down faster. Explain a surface-area mechanism, distinguish observation from inference, and connect digestion with absorption.

Answer and explanation

Faster breakdown in B is consistent with increased exposed surface for enzyme contact under the stated conditions. The result is evidence about breakdown rate, not proof that absorption or energy use has already occurred. Further measurements could check the products and their passage across an exchange surface. Other changed conditions would weaken the isolated surface-area explanation.

Identify comparable mass and conditions.

Connect smaller pieces with more exposed surface.

Separate breakdown from later boundary crossing.

Response criteria

Explain the relevant biological process accurately.
Use the supplied evidence and show calculation steps with units where needed.
Connect a labeled model or mechanism with the claim.
State an assumption, evidence limitation, or useful next observation.

Problem 3

Which describes absorption?

Food crosses the intestinal lining into transport
Chewing reduces piece size
A diagram label gets larger
All energy is created

Answer and explanation

Food crosses the intestinal lining into transport

Absorption is boundary crossing; chewing is mechanical processing.

Taught alongside

Elsewhere

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