SEC G3 Combined Science Biology component K327/K328
B4: Nutrition in Humans
Trace digestion, absorption, hepatic portal transport, liver roles, hormones, blood-glucose control, and type 2 diabetes.
Reviewed for the 2027 cohort on 19 July 2026. The official syllabus remains authoritative for assessable wording and paper details.
Core notes
Human nutrition follows food through digestion and absorption, then tracks how the liver and hormones manage the absorbed products.
Digestive organs and enzymes
The mouth ingests, chews, and mixes food with saliva; salivary glands release amylase; and the oesophagus moves the bolus to the stomach. The stomach churns food, provides acidic conditions, and begins protein digestion. The duodenum receives digestive enzymes from the pancreas and bile made by the liver and stored in the gall bladder.
The ileum completes digestion and absorbs soluble products into blood. The colon reabsorbs water, the rectum stores faeces, and the anus controls egestion. Absorbed nutrients are assimilated when cells and organs use or store them.
Amylase changes starch to maltose, maltase changes maltose to glucose, proteases change proteins to amino acids, and lipase changes fats to fatty acids and glycerol. Match each enzyme to substrate and end-products.
Hepatic portal transport and liver roles
The hepatic portal vein carries blood rich in absorbed nutrients from the small intestine to the liver before it enters general circulation.
The liver converts glucose and glycogen in both directions, contributes bile to fat digestion, processes amino acids and forms urea, and breaks down alcohol and hormones.
Hormones, glucose control, and type 2 diabetes
A hormone is made by a gland, transported in blood, and changes the activity of specific target organs. When blood glucose rises, insulin promotes its removal from blood and storage; when it falls, glucagon promotes release of glucose from glycogen.
Type 2 diabetes produces persistently high blood glucose because tissues resist insulin or too little insulin is made. Risk increases with an unhealthy diet and sedentary lifestyle. Management can include dietary change, activity, mass management, monitoring, and prescribed medical care.
Formulae and relationships
This chapter is assessed mainly through models, field patterns and explanations. Build the causal chain before adding any calculation.
Worked examples
Example 1: After a carbohydrate-rich meal, which hormone response lowers blood glucose?
- Digestion and absorption raise blood glucose.
- The pancreas increases insulin release.
- Target tissues take up glucose and the liver stores some as glycogen.
Answer: Insulin promotes glucose removal from blood and storage, lowering the concentration.
Chapter checkpoint
Use these three moves to organise the topic before attempting a mixed or practical question.
- Explain Digestive organs and enzymes with the named terms, evidence, and causal links kept distinct.
- Use Hepatic portal transport and liver roles to interpret the evidence given and justify each conclusion.
- Apply Hormones, glucose control, and type 2 diabetes to a new example, then check the conclusion against the information given.
Official outcome coverage
K327 B4: 8 mapped outcomes, references B4(a), B4(b), B4(c), B4(d), B4(e), B4(f), B4(g), B4(h). Check the official K327 syllabus.
K328 B4: 8 mapped outcomes, references B4(a), B4(b), B4(c), B4(d), B4(e), B4(f), B4(g), B4(h). Check the official K328 syllabus.
The outcome wording is not reproduced here. The relevant official syllabus remains authoritative for exact assessable scope.
Practical and data connection
Interpret digestion, absorption or blood-glucose data and connect each pattern to the named organ, enzyme, hormone or liver role. Use only safe model or data work for human samples and do not collect bodily fluids in breach of school rules.
Exam traps and retrieval check
Avoid these traps
- Putting bile production in the gall bladder.
- Sending absorbed nutrients directly to the heart instead of through the hepatic portal vein and liver.
- Describing type 2 diabetes as complete absence of glucose.
Check from memory
What does lipase produce?
Fatty acids and glycerol.
What does the hepatic portal vein carry?
Nutrient-rich blood from the small intestine to the liver.
Which hormone raises low blood glucose?
Glucagon.
Official Combined Science scope
This shared Combined Biology owner serves both K327 and K328. Digestive-system functions, digestive enzymes, hepatic portal transport, liver roles, hormones, blood-glucose control, and type 2 diabetes.