Connect digestive structures to breakdown, absorption and transport of nutrients.
Method and worked examples
Digestion breaks food down physically and chemically. Chewing reduces piece size; digestive enzymes help split particular large molecules into smaller molecules. Food passes through mouth, oesophagus, stomach and small intestine, then remaining material enters the large intestine. Egestion removes undigested waste.
Absorption moves digested nutrients across the small-intestine lining into internal transport fluids. Villi increase surface area; thin surfaces and nearby blood supply support uptake and transport to cells. The large intestine absorbs water from remaining contents. Distinguish breaking molecules down from moving them across a surface: the first is digestion, the second absorption.
Example 1
Is cutting a food molecule into smaller molecules digestion or absorption?
Digestion: it changes food into smaller molecules. Crossing the gut lining is absorption.
Example 2
How do villi support the small intestine’s function?
They increase surface area for absorbing digested nutrients, which can then be transported to cells.
Watch out:Digestion breaks food down; absorption moves the resulting nutrients across a surface into the body.
Digestion and absorption | Year 8 Science | Ascent Arcade