Upload
emerald-terry
View
221
Download
0
Tags:
Embed Size (px)
Citation preview
Enzymes in Digestion
Text p.168
Syllabus • Some enzymes work outside the body cells. • The digestive enzymes are produced by specialised cells in
glands and in the lining of the gut. The enzymes then pass out of the cells into the gut where they come into contact with food molecules.
• They catalyse the breakdown of large molecules into smaller molecules.
• The enzyme amylase is produced in the salivary glands, the pancreas and the small intestine. This enzyme catalyses the breakdown of starch into sugars in the mouth and small intestine.
• Protease enzymes are produced by the stomach, the pancreas and the small intestine. These enzymes catalyse the breakdown of proteins into amino acids in the stomach and the small intestine.
• Lipase enzymes are produced by the pancreas and small intestine. These enzymes catalyse the breakdown of lipids (fats and oils) into fatty acids and glycerol in the small intestine.
Digestive system sequencing
• Use cards
Table of digestive enzymes
Nutrient Enzymes used Where enzyme made
Part of digestive system in which digestion occurs
Product
Carbohydrate(starch)
amylase Salivary glandsPancreasSmall intestine
MouthSmall intestine
Simple sugars (eg GLUCOSE)
Protein Protease StomachSmall intestine
StomachSmall intestine
Amino acids
Lipid(fats and oils)
Lipase PancreasSmall intestine
Small intestine Fatty acids and glycerol
A cell which produces enzymes makes protein (enzymes are proteins)
Carbohydrates (polymers) are chains of identical sugar molecules (monomers). The enzyme that digests carbohydrates must be able to break the chemical bonds between the individual sugar molecules.
The product of the chemical breakdown of carbohydrates is sugar. The sugar is known as glucose.
Enzymes that digests carbohydrates are known as carbohydrases.
Digestive enzymes:
sugar
sites of enzyme attack
The digestion of carbohydrates can be represented by the following equation.
SugarsCarbohydratescarbohydrase
Enzyme driven reaction
As with carbohydrates, proteins are made of chains of chemicals. However, instead of the chain containing identical molecules, in protein these molecules are different.
Protein is made up of chains of amino acids. There are over 20 different kinds of amino acid.
Proteins and amino acids
Imagine a bead necklace made up of over 20 different kinds of bead.
amino acids sites of enzyme digestion
Enzymes for digesting proteins
sites of enzyme attack
The enzymes that digest proteins must be able to break the chemical bonds between the different amino acids.
Enzymes that digest protein are known as proteases.
amino acids
The digestion of proteins can be represented by the following equation.
proteaseProtein Amino Acids
Fat in our food
site of enzyme attack
The enzymes that digest fats must be able to break the chemical bonds between the glycerol phosphates and the fatty acids.
Fats are also known as lipids.
Fats are made up of a molecule of glycerol attached to three fatty acid molecules.
fatty acids
glycerol
Fat digestion can be represented by the following equation:
lipaseFat Fatty Acids + Glycerol
The enzymes that digest fats must be able to break the chemical bonds between the glycerol phosphates and the fatty acids.
Fats are also known as lipids.
Enzymes that digest fat (lipid) are known as lipases.
Enzymes for digesting fat
Of these three enzymes, the only one that is released within the mouth is carbohydrase. This is partly because the conditions within the mouth are suitable for carbohydrase action.
Carbohydrase in saliva
It works best within an alkaline (pH > 7) environment.
The carbohydrase in saliva in combination with other digestive carbohydrases added later from the pancreas and the small intestine complete carbohydrate digestion.
The food could now pass down either the trachea (windpipe) or the gullet/oesophagus.
sugars
chemically and physically digested
physically digested
physical digestion
chemical digestion
CarbohydratesFatsProteins
Digestive action of the mouth - summary