O Level Biology

Describe the structure of a villus and the roles of capillaries and lacteals

Understand that assimilation is the uptake and use by cells of nutrients from the blood

Understand that absorption (by diffusion, osmosis and active transport) is the movement of nutrients from the intestines into cells lining the digestive system and then into the blood

State that the small intestine is the region where nutrients are absorbed

Describe peristalsis as waves of contractions of longitudinal and circular muscles which move food through the digestive system

Outline the role of bile in emulsifying fats to increase the surface area for the chemical digestion of fat to fatty acids and glycerol by lipase

Understand that the different proteases present in the stomach and the duodenum work best at different pH levels

Describe the function of hydrochloric acid in the stomach as killing ingested bacteria

Describe the functions of amylase, maltase, protease and lipase, listing the substrates and endproducts, limited to: (a) amylase breaks down starch to maltose (b) maltase breaks down maltose to glucose (c) protease (pepsin and trypsin) breaks down protein to amino acids (d) lipase breaks down lipids to fatty acids and glycerol

State that physical digestion increases the surface area of food for the action of enzymes in chemical digestion