Locate nutrient absorption in the small intestine
Distinguish movement across the lining from movement along the canal.
Section B7.5 · Absorption
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall large and small nutrient molecules, cell membranes and enzyme specificity.
- Use the stated diagram keys and evidence; models are not to scale.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which organ region is the main nutrient-absorption site?
What you will learn
- Distinguish movement across the lining from movement along the canal.
- Interpret diagram arrows by the action they represent.
Across a barrier
The small intestine is the main region where nutrients are absorbed. Absorption involves movement of small nutrient products across its epithelial lining into the body’s transport systems, rather than merely pushing food along the tube.
In the Core account, nutrients move from intestines into blood. The Extended lessons explain the villus structures and the lymphatic route for much absorbed lipid material.
Digestion and uptake can occur nearby
Chemical digestion provides products such as sugars and amino acids near the lining. Transport across that lining is absorption. The presence of an enzyme in the lumen does not itself prove a nutrient crossed into a vessel.
Blood then transports absorbed products toward tissues; cell uptake and use is assimilation. Keep these stages distinct when explaining a diagram or interpreting concentrations.
Sources for this lesson
Pause and explain
Which event distinguishes absorption?
Worked example
Glucose appears on the tissue side of a suitable intestinal-lining model after being on the lumen side. Which process is represented?
Show the worked solution
- There is movement across a lining.
- Name absorption.
- Do not call mere glucose presence proof of respiration.
Answer Absorption, represented by nutrient movement across the lining.
Try a topic test
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Name the region of nutrient absorption and define the movement in the Core account.
Give me a hint
Use small intestine and blood.
Compare my reasoning
- Small intestine.
- Nutrients move from intestine into blood.
Small intestine; nutrients move from the intestines into the blood.
Look for these in your work
- Region.
- Correct direction.
Why is an arrow along the centre of the intestinal tube not automatically an absorption arrow?
Give me a hint
Absorption crosses the lining.
Compare my reasoning
- Along-lumen movement transports contents.
- Across-lining movement is needed for absorption.
The arrow may show movement of contents along the canal rather than nutrients crossing its wall.
Look for these in your work
- Directional distinction.
- Use the arrow key.
A model produces glucose but no movement across a barrier is measured. Which stage is supported and which remains unverified?
Give me a hint
Production and transfer need separate observations.
Compare my reasoning
- Glucose production can support digestion.
- Absorption is unmeasured.
Digestion may be supported; absorption remains unverified without barrier-crossing evidence.
Look for these in your work
- Supported stage.
- Unverified stage.
Common mistakes
- Along the tube and across the wall differ.
- Sugar production alone does not prove absorption.
What can you explain now?
Which event distinguishes absorption?
Compare with the explanation
A nutrient crosses the intestinal lining.
The barrier is crossed.
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Make it stick
Explain absorption using a direction across a lining.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.