Digestion Flashcards
Enzyme
A protein that acts as a catalyst and so lowers the activation energy needed for a reaction.
Absorption
Movement of digested food molecules through the wall of the intestine into the blood or lymph
Oesophagus
Muscular tube which carries food from the mouth to the stomach
A muscular sac with an inner layer that produces enzymes. Its role is so store and digest food, especially proteins.
Stomach
A long muscular tube where food is further digested. Enzymes are produced by its walls and by glands that pour their secretions into it. Inner walls are folded into villi which gives them a large surface area. Where products of digestion are absorbed into the bloodstream.
Ileum
Where water is absorbed.
Large intestine
The final section of the intestines where the faeces is stored before being egested by the anus.
Rectum
Salivary glands
Situated near the mouth. They pass their secretions via a duct into the mouth which contain salivary amylase which hydrolyses starch into maltose.
A large gland situated below the stomach. It produces a secretion called pancreatic juice, which contains proteases to hydrolyse proteins, lipase to hydrolyse lipids and amylase to hydrolyse starch.
Pancreas
Type of digestive enzyme which hydrolyse carbohydrates, ultimately to monosaccharides.
Carbohydrases
Type of digestive enzyme which hydrolyse lipids (fats and oils) into glycerol and fatty acids.
Lipases
Proteases
Type of digestive enzyme which hydrolyse proteins, ultimately into amino acids.
Produced by the salivary glands and released into the mouth and starts hydrolysing starch in food to maltose.
Salivary amylase
Pancreatic amylase
Produced by the pancreas and released into the small intestine where it continues the hydrolysis of starch to maltose.
Maltase
Produced by the epithelial lining and is a membrane-bound disaccharidase which breaks down maltose into glucose.
An enzyme which is not released into the lumen of the ileum but is part of the cell-surface membranes of the epithelial cells that line the ileum. E.g. maltase
Membrane-bound disaccharidase
Sucrase
Produced by the epithelial lining and is a membrane-bound disaccharidase which breaks down sucrose into the monosaccharides glucose and fructose.
Produced by the epithelial lining and is a membrane-bound disaccharidase which breaks down lactose into the monosaccharides glucose and galactose.
Lactase
Produced by the liver and split up lipids into tiny droplets called micelles.
Bile salt
Emulsification
The process by which lipids are split up into tiny droplets called micelles by bile salts, which are produced by the liver. It increases the surface area of the lipids so that the action of lipases is sped up.
Micelles
Tiny structures (4-7nm in diameter) formed when monoglycerides and fatty acids remain in association with the bile salts that initially emulsified the lipid droplets. They break down as they come into contact with the epithelial cells lining the villi of the ileum and release the monoglycerides and fatty acids which diffuse across the cell membrane into the epithelial cells.
A structure formed when triglycerides associate with cholesterol and lipoproteins, which are adapted for the transport of lipids. Start forming in the endoplasmic reticulum and continuing in the Golgi apparatus.
Chylomicrons
Lymphatic capillaries that are found in the centre of each villus, where chylomicrons pass into and then enter the bloodstream.
Lacteals
Exocytosis
The outward bulk transport of materials through the cell-surface membrane. How chylomicrons move out of the epithelial cells by this process.
Endopeptidases
A type of protease which hydrolyses the peptide bonds between amino acids in the central region of a protein molecule forming a series of peptide molecules.
A type of protease which hydrolyses the peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases. They progressively release dipeptides and single amino acids.
Exopeptidases
Dipeptidases
A type of protease which hydrolyse the bond between the two amino acids of a dipeptide. Dipeptidases are membrane-bound, being part of the cell-surface membrane of the epithelial cells lining the ileum.
The cavity of the intestines
Lumen
Villi
Folded finger-like projections of the ileum wall, about 1mm long, which are increase the surface area of the ileum and therefore accelerate the rate of absorption.
Tiny finger-like projections from the cell-surface membrane of some animal cells.
Microvilli
