Digestion 3 Flashcards
what are the three types of carbohydrates
polysaccharides
disaccharides
monosaccharides
two are the two types of polysaccharides
starch and cellulose
what are the three types of disaccharides
sucrose, maltose, and lactose
what are the three types of monosaccharides
glucose, fructose, galactose
what type of carbohydrates can humans absorb?
monosaccharides
the other types have to be broken down further into things we can digest
what is starch broken down into
individual glucose molecules
how are carbohydrates broken down in the oral cavity
broken down by salivary amylase produced by salivary glands
starch molecules are made of glucose molecules; salivary amylast breaks the bonds between the glucose molecules
why can’t carbohydrates be broken down in the stomach
salivary amylase is inavtivated by the stomach’s chyme
carbohydrates must be broke down in the small intestine
how are carbohydrates broken down in the small intestine
broken down by pancreatic amylase produced in the pancreas
pancreatic amylase continues digestion of starch
we get maltose, glucose, and oligosaccharide strand
brush border enzymes complete starch breakdown
which three brush boarder enzymes complete starch breakdown
dextrinase, glucoamylase, and maltase
how do dextrinase and glucoamylase work to complete starch breakdown
break bonds between glucose subunits of oligosaccharides
how does maltase work to complete starch breakdown
breaks bonds between a maltose molecule (molecule with 2 glucose molecules)
what does lactase do
digests lactose molecule into glucose and galactose
what does sucrase do
digests sucrose molecule into glucose and fructose
explain how monosaccharides are absorbed
transported across the intestinal epithelial lining and into the blood by secondary active transport
sodium and potassium are pumped against their concentration gradient using a sodium/potassium ATPase pump
energy created allows monosaccharides to move through a monosaccharide carrier into the blood
they move across the basolateral membrane by facilitated diffusion then enter blood via intercellular clefts
where do monosaccharides go once they get into blood and what are they used for there
once in the venous blood, monosaccharides go to the liver
fructose and galactose converted to glucose
glucose can then be used for energy, converted and stored as glycogen, or converted into fat
how is protein broken down in the stomach
pepsinogen is activated to become pepsin
pepsin denatures proteins to facilitate chemical breakdown
what is the fiber adding bulk to the lumen content
cellulose, a carbohydrate component of plant cell wall that we can’t digest
what is the structure of a protein molecule
polymer made of amino acid subunits that are linked by peptide bonds
how is protein digested in the stomach
starts to be digested by the activated form of pepsinogen, pepsin
how is protein broken down in the small intestine
enzymes released from the pancreas continue protein digestion
what are the 3 enzymes released by the pancreas to assist protein breakdown in the small intestine
trypsinogen, chymotrypsinogen, and procarboxypeptidase
where is enteropeptidase released from and what does it do
released from brush border of epithelial cell
activates trypsinogen to trypsin
what does trypsin do
activates more trypsinogen to trypsin
activates chymotrypsinogen to chymotrypsin
activates procarboxypeptidase to carboxypeptidase
also breaks bonds between specific amino acids to produce smaller strands of peptides
what do trypsin and chymotrypsin do
break bonds between specific amino acids to produce smaller strands of peptides
what does carboxypeptidase do
breaks bonds between amino acids on carboxyl end and the remaining protein
where is dipeptidase released from and what does it do
released from brush border of epithelial cells
breaks final bond between two amino acids
what does aminopeptidase do
generates free amino acids which are used as building blocks for new proteins or converted into glucose
what is a triglyceride molecule made of
glycerol and three fatty acids
what are the 2 enzymes that break down lipids in the stomach
lingual lipase and gastric lipase
what produces gastric lipase
chief cells of the stomach
how is lipid digested in the stomach
lingual lipase and gastric lipase digest 30% of triglycerides to diglyceride and fatty acid
how are lipids digested in the small intestine
pancreatic lipase digests triglycerides (in micelles) into monoglycerides and two fatty acids
requires triglycerides to be emulsified first
how does emulsification work for lipid digestion
bile salts from the liver and gallbladder emulsify lipid droplets to form micelles
explain the organization of a micelle
molecules with polar head and nonpolar tail
nonpolar tails line up around fat droplet with heads toward the aqueous fluid
allows greater access of pancreatic lipase to triglyceride
how are lipids absorbed
monoglycerides and free fatty acids are transported to epithelial lining by micelles
they enter the cells, bile salts stay in the lumen
in the cell, monoglycerides and free fatty acids re-form into triglycerides and are wrapped in protein to form chylomicrons
chylomicrons are released by exocytosis and enter lacteals to get to the blood
what are nucleic acids and what are the two types
polymers of nucleotides
DNA and RNA
what makes up a DNA and RNA molecule
sugar, phosphate group, and nitrogenous base
how are nucleic acids broken down in the small intestine
deoxyribonuclease and ribonuclease released by the pancreas break phosphodiester bonds between nucleotides of DNA and RNA
phosphatase and nucleosidase from brush border
phosphatase breaks bonds holding phosphate
nucleosidase breaks bonds between sugar and nitrogenous base
what is hepcidin and what does it do
hormone released from the liver
inhibits absorption of iron
which vitamins are water soluble and how are they absorbed
B and C
absorbed through diffusion and active transport
which vitamins are fat soluble and where are they absorped
A, D, E, and K
absorbed in small intestine with lipids
how is water absorbed
by osmosis
where and how are electrolytes absorbed
absorbed mostly in the small intestine
usually unregulated and dependent on diet
how is vitamin B12 absorbed
by receptor-mediated endocytosis
requires intrinsic factor which is formed by parietal cells in the stomach
