Separate assimilation from egestion
Connect cell use and removal of undigested material to different pathways.
Section 7.2 · Digestive system
Core and Extended; Biology 0610, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked
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 example occurs across the intestinal lining?
What you will learn
- Connect cell use and removal of undigested material to different pathways.
- Correct a diagram that mixes digestive and urinary routes.
Assimilation occurs in cells
After absorption, nutrients can be transported to body cells. Assimilation is their uptake and use by cells, for example amino acids becoming new proteins or glucose being used in respiration. It is not another name for crossing the intestinal wall.
A blood vessel carrying glucose is a transport step. A cell taking up and using the glucose is assimilation. Explain the action rather than classifying every event after eating as digestion.
Egestion is a different exit
Undigested food material leaves the body as faeces through the anus: egestion. The rectum stores faeces before their removal. The nutrients already used by cells do not simply return to the gut as unchanged food.
Excretion removes metabolic waste made by cells, such as urea. A syllabus response should not treat faeces and urea as the same material or confuse the digestive route with the urinary route.
Pause and explain
Which event is egestion?
Worked example
A cell makes protein from absorbed amino acids while undigested material leaves through the anus. Name the events.
Show the worked solution
- Cellular nutrient use: assimilation.
- Faeces removal: egestion.
- Neither is nutrient crossing the intestinal wall.
Answer Assimilation; egestion.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
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.
Define assimilation and egestion.
Give me a hint
Use cell uptake/use versus faeces removal.
Compare my reasoning
- Assimilation: uptake/use of nutrients by cells.
- Egestion: removal of undigested food as faeces.
Assimilation is cellular uptake and use of nutrients; egestion removes undigested food as faeces.
Look for these in your work
- Both definitions.
- Correct locations.
Classify: glucose crosses gut wall; glucose is used by a muscle; faeces leave anus.
Give me a hint
Follow action in order.
Compare my reasoning
- Absorption.
- Assimilation.
- Egestion.
Absorption; assimilation; egestion.
Look for these in your work
- All three.
- No digestion/transport confusion.
A diagram sends undigested food from rectum to kidney before leaving. Explain the route error.
Give me a hint
The canal ends through the anus.
Compare my reasoning
- Faeces leave through anus.
- Kidneys belong to a different waste-removal route.
Undigested material is egested through the anus; it is not sent through the kidneys as faeces.
Look for these in your work
- Correct food route.
- Separate excretion system.
Common mistakes
- Absorption and assimilation differ in action and location.
- Egestion and excretion are not synonyms.
What can you explain now?
Which event is egestion?
Compare with the explanation
Undigested food leaves as faeces.
That is the defined digestive exit.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Give one example each of absorption, assimilation, egestion and excretion.
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.