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biology 0610printed 86 · PDF 86
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Once food is ingested, it undergoes both mechanical and chemical digestion.
Mechanical/Physical digestion breaks food down into smaller parts without chemical
altering it, thereby increasing the surface area and making chemical digestion easier.
This is done by the mouth and alimentary canal/oesophagus. Chemical digestion
involves breaking down large insoluble molecules to smaller, more soluble molecules,
with the use of enzymes - so absorption can take place more efficiently.
Passage of food down the digestive tract:
Mouth and Salivary glands: contains teeth which mechanically digest food. Enzymes
(amylase) start to work on starch, starting to chemically digest it
Oesophagus: food passes from mouth to stomach, contraction of muscles enables
peristalsis which allows for more mechanical digestion
Stomach: hydrochloric acid is present which provides a condition of ph 2. The
Protease enzyme pepsin works here in optimum ph, to produce amino acids. Acid
kills bacteria by providing extremely acidic conditions.
Duodenum: first part of small intestine. Acidity from the stomach is neutralized. Fats
are emulsified through bile and digested by pancreatic lipase to form fatty acids and
glycerol. Pancreatic trypsin breaks down starch to simple carbohydrates such as
maltose
Ileum: maltase breaks down maltose to glucose, absorption takes place here
Pancreas: produces amylase, trypsin, lipase
Liver: produces bile which neutralizes acidic fat molecules, helping in production of
alkaline ph of trypsin. Bile is stored in gallbladder and secreted to duodenum through
bile duct
Colon: first part of large intestine. Reabsorption of water. Indigestible food passes
through
Rectum: second part of large intestine. Faeces are stored here and expelled through
anus
Teeth:
Incisors
Canines
PreMolars
Molars
rectangular
shape, for cutting
and biting of food
sharp and pointed.
Used for tearing and
piercing food. Used by
predators to kill prey
Chewing and
grinding, blunt,
have one ridge
Further chewing
and grinding,
have two ridges