Human nutrition

• Human Nutrition is a topic in Biology under the CIE 7 syllabus.
• Human Diet & Digestion is a subtopic in Human Nutrition.
• Digestive System is a subtopic in Human Diet & Digestion.
• Physical Digestion is a subtopic in Human Diet & Digestion.
• The process that takes place during physical digestion helps to increase the surface area of food for the action of enzymes during chemical digestion.
• Physical digestion is mainly carried out by the chewing action of the teeth, the churning action of the stomach, and the emulsification of fats by bile in the duodenum.
• Physical Digestion is the breakdown of food into smaller pieces without chemical change to the food molecules.
• Teeth & Digestion is a subtopic in Human Diet & Digestion.
• The digestive starch of amylases is starch.
• Amylases are produced in the mouth and pancreas (secreted into the duodenum).
• The digestive proteins of amylases are proteins.
• Amylases digest starch into smaller sugars.
• Amylases digest lipids into smaller fatty acids and glycerol.
• Amylases break down proteins into smaller peptides.
• The digestive lipids of amylases are lipids.
• Emulsification of Fats & Oils: Extended is a subtopic in Human Diet & Digestion.
• Chemical Digestion is a subtopic in Human Diet & Digestion.
• Revision Notes, Topic Questions, Past Papers
• Bile breaks down large drops of fat into smaller ones.
• The enzymes in the small intestine have a higher (more alkaline) optimum pH than those in the stomach.
• The structure of a villus is related to its function, which comes up frequently in exam questions.
• This process is known as emulsification.
• Bill contains extended cells in the liver product which is stored in the gall bladder.
• Emulsification is an example of mechanical digestion, not chemical digestion – breaking something into smaller pieces does not break bonds or change the chemical structure of the molecules which make up the molecule.
• The larger surface area allows lipase to chemically break down the lipid into glycerol and fatty acids faster.
• Lacteal runs through the center of the villus to transport fats away from the small intestine.
• The villus is well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine.
• The wall of the villus is one cell thick meaning that there is only a short distance for absorption to occur by diffusion.
• Revision Notes, Topic Questions, Past Papers cover the small intestine on the surface of the villus for further absorption of nutrients.
• This is an example of mechanical digestion, not chemical digestion – breaking something into smaller pieces does not break bonds or change the chemical structure of the molecules which make up the molecule.
• The ileum is adapted for absorption as it is very long and has a highly folded surface with millions of villi (tiny, finger-like projections).
• Food taken into the body goes through five different stages during its passage through the alimentary canal: ingestion, digestion, absorption, excretion, and storage.
• Digestion of food goes through five stages during its passage through the alimentary canal: ingestion, digestion, absorption, excretion, and storage.
• Emulsification is the equivalent of tearing a large piece of paper into smaller pieces of paper.
• The larger surface area allows lipids to chemically break down the lipid into glycerol and fatty acids faster.
• Nutrients are absorbed in the small intestine.
• These adaptations of the small intestine significantly increase the surface area, allowing for more efficient absorption.
• Water is absorbed in both the small intestine and the colon, but most absorption of water (around 80%) happens in the small intestine.
• Absorption is the movement of digested food molecules from the digestive system into the blood (glucose and amino acids) and liver (fatty acids and glycerol).
• Chemical digestion is the breakdown of large, insoluble molecules into smaller, soluble molecules.