Digestion & Absorption Flashcards
what is the function of vitamins A, C and D?
A - vision
C - antioxidant
D - calcium absorption
what are the functions of calcium and iron minerals?
calcium - bone mineralisation
iron - oxygen transport
what are the 3 main types of carbohydrates?
monosaccharide, disaccharide, polysaccharide
what are the 3 types of monosaccharides?
glucose, fructose, galactose
how does the body digest large molecules in food?
breaks down into smaller molecules that the body can absorb
e.g protein -> peptide -> amino acid
what is the definiton of digestion?
the process of food being broken down into components simple enough to be absorbed into the intestine
what enzyme secretions aid digestion?
glandular cells (mouth)
chief cells (stomach)
exocrine cells (pancreas)
enzymes bound to apical membrane of enterocytes
what 3 glands produce saliva?
parotid, submandibular, sublingual
what is the function of saliva?
begins carbohydrate digestion (using alpha amylase)
begins lipid digestion (using lingual lipase)
what is a zymogen?
an inactive precursor (protein containing an inactive enzyme) that is activated by the cleavage of a specific peptide bond
what does bile do in digestion?
emulsifies fats to allow enzymes to access them
what are bile acids derived from?
cholestorol
how is bile conjugated and what does it become?
conjugated to amino acid, becomes amphipathic (both hydrophobic/hydrophilic components)
explain the functions of each small intestine component in digestion
duodenum - mixing secretions with food, acid neutralisation, further digestion, absorption
jejunum - completing breakdown, nutrient absorption
ileum - nutrient absorption
explain how enterokinase activates various digestive proteins in the pancreas
enterokinase in the duodenum turns inactive trypsinogen into active trypsin, which can activate various other digestive proteins
(e.g proelastase -> elastase)
what are the brush border enzymes? give examples
enzymes tethered to plasma membrane composed of numerous microvilli
examples - peptidases, lactase, sucrase, maltase
what is mastication and what does the food become after mastication?
chewing
breaks up food and moistens it, becomes bolus
what digestion occurs in the stomach?
protein digestion - HCL denatures proteins and activates pepsin (endopeptidases that break down proteins into small peptides)
lipids - gastric lipase present but minor contribution
what carbohydrate digestion occurs in the duodenum?
alpha amylase digests starch
brush border enzymes turn disaccharides into monosaccharides
what protein digestion occurs in the duodenum? (+ naming the enzymes)
cleaved by trypsin, chymotrypsin, elastase and carboxypeptidases to produce smaller peptides
brush border enzymes turn peptides into amino acids
what lipid digestion occurs in the duodenum?
pancreatic lipase digests lipids to monoglycerides and fatty acids
phospholipase digests phospholipids to lysolecithin and fatty acids
what 3 ways are nutrients absorbed?
passive absorption (diffusion)
facilitated transport (involved membrane carrier)
active transport (ATP needed)
how are lipids absorbed?
in mixed micelles, they diffuse down conc. gradients into cells
how do chylomicrons form and enter circulation?
triglycerides of above 12 carbons are formed into a chylomicron
then secreted into lymphatics through lacteals, where they end up in the bloodstream eventually
how are monosaccharides absorbed?
sodium co-transporters, transported across basolateral membrane by glut-2 transporter
how are amino acids absorbed?
sodium co-transporters and facilitated diffusion
