ch 23 digestive system p4 Flashcards
primary method of absorption and digestion
enzymatic hydrolysis, breaks down large food molecules to monomers
most digestion occurs in the
small intestine, where pancreatic enzymes break large to small down, brush border enzymes breakdown various molecules into monomers.
why Is lipid digestion hard
triglycerides love to stick together, slower n more complicated
absorption
substances move though enterocytes from apical membrane then to basal membrane of small intestine
substances pass through where to get transported
interstitial fluid then capillaries
which substance is absorbed passively through absorption
non polar bc its lipid soluble. the rest is active
can stuff be absorbed into small intestine before being broken into monomers
no! has to be monomer, simplest form
3 sources for carbohydrate digestion and absorption
polysaccharides- starch and glycogen
disaccharides- sucrose, lactose, maltose
monosaccharides- glucose, fructose, galactose
what do polysaccharides breakdown to
oligosacharides, chains of 2-8 glucose molecules linked together. these are the hardest to breakdown.
starch breakdown begins in the
mouth
monosaccharides
carb monomers absorbed by small intestine, smallest which we absorb
process of polysaccharide breakdown
broken to oligosacharides and disaccharides by pancreatic amylase
brush border enzymes dextrine and glucoamylase breakdown the disach/oligosach into monosach
monosach transports through enterocyte
monosach exit enterocyte at basal membrane via facilitated diffusion entering bloodstream via intracellular clefts and goes away
which monosachs get transported and how
glucose and galactose via secondary active ( Na+ follows these monomers) transport and fructose via facilitated diffusion.
sources of proteins for digestion and absorption
dietary, enzyme, and proteins from sloughed off disintegrating mucosal cells.
monomer of protein
amino acid
protein breakdown process
broken down by pancreatic proteases, trypsin and chymotrypsin break down larger proteins to smaller fragments, carboxypeptides split off individual amino acids
brush border enzymes split off remaining protein fragments into individual amino acids
amino acids cotransport into enterocyte
amino acids exit enterocyte via facilitated diffusion and enter blood via intracellular clefts
lipid sources and monomers
fatty acid and monogluycerides are the monomers, and triglycerides are the sources.
digestion begins where
small intestine, pancreatic juices containing lipases and bile necessary for fat digest.
process of lipid breakdown
emulsification, pancreatic lipase, micelle, move into enterocyte via simple diffusion, chylomicron formation, then chylomicron is transported out via exocytosis
emulsification of lipids
bile salts from bile break down large fat globule into smaller fat droplets. important bc smaller fat droplets have increased SA. it won’t break chemical bonds, so its not a digestive process so digestion can occur
pancreatic lipase of lipids
breaks down triglycerides to fatty acids and monoglycerides
micelle formation of lipids
fatty acids and monoglycerides associate with bile salts again to form micelles. without micelles, fatty acids and monoglycerides would float to chyme surface and won’t transport to enterocyte.
chylomicron formation of lipids
once lipids enter enterocyte via simple diffusion, triglycerides are made from fatty acids and monoglycerides. combined with various other molecules and coated with water soluble proteins to form chlyomicron. water soluble so it can travel thru blood
chlyomicron transported out enterocyte by
exocytosis, bc too large to go through capillary walls, so pumped straight into lacteals of lymphatic system, then exit lymph system into venous blood.
nucleic acid digestion and absorption
pancreatic nucleases hydrolyze nucleic acids from the nucleotide monomer. brush border enzymes break apart nucleotides into nitrogenous bases, pentose sugars, phosphate ions. enter blood after transporting across small intestine.
vitamin absorption
A D E K fat soluble only, can only be absorbed with a triglyceride source ex, taken with food to be digested
B C water soluble only
water absorption
95% of water absorbed in small intestine, almost rest by large intestine. 0.1 L leaves body with feces.
electrolyte absorption
sodium and potassium
sodium absorption
coupled with movement of glucose and amino acids, moves into enterocyte on apical surface with monomers, pumped via N and K pump
potassium absorption
K moves into mucosa by facilitated diffusion, K absorption influenced by water absorption, usually inhibit water absorption inhibits K absorption
