Human Nutrition

Small and large intestine anatomy

The small intestine consists of three parts

-Duodenum

-Jejunum

-Ileum

Stomach

Has a Ph of 1-2

HCl - hydrochloric

protease, Lipase, Amylase are the pancreas enzymes

Have Ph 7-8

Liver Bile has a Ph 12

Bile neutralises the acid otherwise the enzymes will become denatured

Process in the digestive system

Eating food involves several different processes

  1. Ingestion - the taking of the substances into the body

  2. Digestion - the break down of the food

  3. Absorption - the movement of nutrients from the intestines into the blood

  4. Assimilation - the uptake and use of nutrients by cells

  5. Egestion - the removal of undigested food from the body as faeces

The difference between Egestion and Excreation

Excreation is the removal to the waist made by a chemical reaction

Egestion is the removal undigested food from the body

Physical Digestion

  • large pieces of food are broken down into smaller pieces by teeth and the churning movements of the stomach

  • Does not involve any chemical change to food molecules

  • Increases surface area for the action of the enzymes in chemical digestion

Chemical digestion

  • large insoluble food molecules are broken down by the action of enzymes into small soluble molecules

Enzyme

substrate

where enzyme is secreted

where enzyme acts

products

Amylase

Ph7

Starch

Salivary glads

Pancreas

Mouth

duodenum (Small Intestine)

Simple sugars

Protease

Protein

Stomach

Pancreas

Stomach

Duodenum

amino acids

Lipase

Ph7-8

Lipids (fats/oils)

Pancreas

duodenum

Fatty acids + glycerol

amylase maltase

Starch ————→ maltose ————→ glucose

Hydrochloric acid in the Stomach

  • Gastric juice contains Hydrochloric acid

  • Kills bacteria by denaturing their enzymes

  • Creates optimum conditions for proteas activity

(Pepsin - stomach protease)

Bile

  • The enzymes made in the pancreas and work best in alkaline conditions

  • Neutralises the acid in the stomach

  • ‘emulsifies fats (increases their surface area) This allowes for the chemicals digestion of fats by lipase

  • Bile neutralises the acid that was added to the food in the stomach as it enters the small intestine and makes it slightly alkaline