unit 3; enzymes and digestion Flashcards
define the digestive system
an exchange surface through which food substances are absorbed
the oesophagus
carries food from the mouth to the stomach
the stomach
muscular sac with an inner layer that produces enzymes- stores and digests food
the ileum
long muscular tube that further digests food further by enzymes it secretes
describe the ileums adaptations
inner walls folded into villi, villi contain microvilli on the epithelial cells of each villi- increased sa for absorption
the large intestine
absorbs water- mainly from secretions of digestive glands
the rectum
faeces stored here before being moved to the anus in egestion
the salivary glands
near the mouth- pass secretions via a duct into the mouth, secretions contain amylase which hydrolyses starch into maltose
the pancreas
large gland near the stomach, produces secretions called pancreatic juice, containing proteases (proteins), lipase (lipids) and amylase (starch)
2 stages of digestion
physical breakdown + chemical digestion
carbohydrases
break down carbs ultimately into monosaccharides
lipases
break down lipids into fatty acids and glycerol
which parts of the body are involved in physical breakdown
the teeth and the stomach (muscles in the stomach wall)
where is amylase produced
mouth and pancreas
where is maltase produced
in the lining of the ileum
where are bile salts produced
liver
what do bile salts do
break lipids into micelles- increase sa of lipids
what do endopeptidases do
hydrolyses the peptide bond between amino acids- forming a series of peptide molecules
what do exopeptidases do
hydrolyse peptide bonds on ends of peptide molecules- forms dipeptides and single amino acids
what do dipeptidases do
hydrolyse bonds in dipeptidases- membrane bound
what happens to micelles when they reach the ileum
they break down, releasing monoglycerides and fatty acids that can diffuse through the membrane into the epithelial cells
what happens after monoglycerides and fatty acids enter epithelial cells
recombine to form triglycerides
what is a chylomicron
special particles adapted for transport of lipids- a combination of triglycerides, cholesterol and lipoproteins
where are chylomicrons formed
in endoplasmic reticulum + golgi apparatus of epithelial cells
