M3 Digestion Flashcards
All digestive enzymes are known as _________.
Hydrolases
What are the 3 types of proteases and where are they produced?
Endopeptidases - stomach
Exopeptidases - Pancreas
Dipeptidases - Epithelial cells of ileum
What do endopeptidases do?
They break peptide bonds within larger polypeptide chains, producing smaller polypeptide chains.
What do exopeptidases do?
They break the terminal peptide bonds (on the ends of the polypeptide chains) releasing dipeptides or amino acids.
What do dipeptidases do?
Hydrolyse the bonds between amino acids.
What are the 5 types of carbohydrases and where are they produced?
Salivary amylase - salivary glands
Pancreatic amylase - pancreas
Maltase - epithelial cells of ileum
Sucrase - epithelial cells of ileum
Lactase - epithelial cells of ileum
What do salivary and pancreatic amylase do?
They break glycosidic bonds - hydrolysing polysaccharides into maltose.
What do Maltase, Sucrase and Lactase hydrolyse? What are the products?
DISACCHARIDES
Maltose - alpha glucose x2
Sucrose - alpha glucose and fructose
Lactose - alpha glucose and galactose
What does lipase do? Where is it produced?
Hydrolyses lipids by breaking ester bonds, forming fatty acids and monoglycerides.
Produced in the pancreas.
What do bile salts do?
Emulsify lipids - increasing SA of lipid droplets for lipase enzyme attachment.
What is the difference between mechanical and chemical digestion?
Mechanical digestion includes the chewing and churning of food - increasing SA
Chemical digestion includes enzyme action and hydrolysis of polymers
How is the ileum adapted to it’s function?
(muscles, villi, lacteal, epithelial cells, capillaries…)
Muscles - contract to mix and propel food
Muscles - contract to project villi into the lumen when food is present, increasing SA
Villus - increases SA, thin-walled
Microvilli - further increases SA
Capillaries - transport absorbed molecules
Lacteal - transports chylomicrons to lymphatic vessels
Epithelial cells - large numbers of ER, golgi apparatus and mitochondria
What are chylomicrons? What are they made out of?
Droplets of fat present in the blood or lymph after absorption from the small intestine.
Made out of triglycerides, cholesterol, phospholipids and protein.
How are lipids absorbed into the bloodsteam?
Lipase -> fatty acids and glycerol
Fatty acids and monoglycerides readily diffuse across the phospholipid bilayer as they are lipid-soluble.
They enter the SER and are resynthesised into triglycerides so they don’t diffuse back out of the cell.
Triglycerides are packaged with cholesterol, phospholipids and protein to form chylomicrons.
Chylomicrons are enclosed in vesicles to leave the cell by exocytosis (into lymphatic vessel)
What are micelles?
Spheres of lipids which form in aqueous solution. Hydrophilic head points outwards, hydrophobic tail points inwards.
