IGCSE Bio - Digestion, absorption and enzymes

Mouth

Where food enters the alimentary canal and digestion begins

Salivary glands

Produce saliva containing amylase

Oesophagus

Muscular tube which moves ingested food to the stomach via peristalsis

Stomach

Muscular organ where digestion continues

Pancreas

Produces digestive enzymes

Liver

Produces bile

Gall bladder

Stores bile before releasing it into the small intestine

Small intestine

Where food is mixed with digestive enzymes and bile and then absorbed into the blood via villi

Large intestine

Where water is reabsorbed

rectum

Where faeces are stored

anus

Where undigested food (faeces) leave the alimentary canal

Carbohydrates

Bodies main source of energy and made up of glucose molecules

Proteins

Used to build and repair tissue, and made up of amino acids

Fats (lipids)

For insulation and used as a long term energy store, as well as to protect (especially vital) organ, made up of fatty acids and glycerol

Enzymes

Biological catalysts for metabolic reactions. They speed up the chemical reactions needed to maintain life.

Substrates

Molecule upon which an enzyme acts

Active site

Area on an enzyme that binds with a substrate to break it down. It is the "lock" in the "lock and key" theory

Protease

Breakdown proteins into amino acids in the stomach and small intestine

Bile

Produced in the liver and stored in the gall bladder, this substance emulsifieis fats and neutralises stomach acid.

Amylase

Breakdown starch into Glucose in the mouth and small intestine

Lipase

Breakdown fats and oils into fatty acids and glycerol in the small intestine

Ingestion

The act of taking food into the body; eating

chemical digestion

Large, insoluble molecules are broken down into smaller, soluble ones

Absorption

The process by which digested molecules are taken from the small intestine and absorbed into the bloodstream.

Assimilation

The act of absorbing molecules from the blood into cells

Egestion

To get rid of as a waste product (undigested food. Not to be confused with excretion)

Lacteal

Part of villi that absorbs fatty acids and glycerol away from the small intestine

Villi

These are tiny little hair-like structures that line the wall of the small intestine and are responsible for the absorption of nutrients

Microvilli

A large number of minute projections that greatly increase the surface area of villi for absorption

Peristalsis

Contraction of circular and longitudinal muscles in the oesophagus and small intestine, creating wave like movements which pushes food along.

Diarrhoea

Passing of watery faeces

fibre

to keep the digestive system healthy and prevent constipation

stomach acid (HCl)

kills bacteria, provides optimum pH for protease

mechanical digestion

Physical breakdown of large pieces of food into smaller pieces without chemical change

Denaturation

loss of normal shape of a protein due to heat or pH change (active site changes)

optimum enzyme conditions

temperature or pH that an enzyme works best at

Incisors

front teeth, cut food

Canines

Teeth in front of the premolars that rip and tear food.

Premolars

crush food

Molars

Back teeth that grind food

Enamel

hardest, outermost layer of a tooth

Dentine

hard, dense, bony tissue forming the bulk of a tooth beneath the enamel.

pulp

The tissue that contains the blood vessels and nerves of a tooth

Cementum

Tissue covering the tooth root

gums

tissue surrounding teeth and bone, protects and provides lubricated surface

nerves and blood vessels

Maintain vitality of tooth

tooth decay

break down of teeth caused by acids made by bacteria. (too much sugar or starch)