Describe what happens to a protein-rich food, such as a piece of chicken, as it passes through the human digestive system.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Protein is broken down by protease enzymes in the stomach and small intestine.
Amino acids are released from the protein chains.
The amino acids are absorbed through the wall of the small intestine.
They enter the bloodstream for transport to cells.
Amino acids are released from the protein chains.
The amino acids are absorbed through the wall of the small intestine.
They enter the bloodstream for transport to cells.
Examiner tips
- Use the exact terms ‘protease enzymes’, ‘amino acids’, ‘stomach and small intestine’, ‘absorbed into the blood’.
- Show the sequence: digestion → breakdown → absorption.
- Keep each point short and to the point.
- Avoid extra words such as ‘in this essay’ or ‘firstly’.
Common mistakes
- Confusing ‘digestion’ with ‘absorption’ in the same sentence.
- Using ‘peptides’ instead of ‘amino acids’ for the final product.
- Mentioning the large intestine or colon, which is not part of protein digestion.
Mark scheme (4 marks)
- Protein is digested / broken down by protease enzymes
- Protein is broken down into amino acids
- Digestion occurs in the stomach and/or small intestine
- Amino acids are absorbed into the blood through the wall of the small intestine
Related
- All WJEC GCSE Biology (Wales) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →