Lab11 Flashcards
Digestion:
a catabolic process that break down large food molecules to monomers.
monomers:
chemical building blocks
digestion is accomplished by…
enzymes secreted into the lumen of the alimentary canal or GI tract by accessory glands
enzymatic breakdown of any food molecule is hydrolsis because
it involves adding a water molecule to each molecular bond to be broken.
most digestion occurs in the..
small intestine
how to pancreatic enzymes help digestion.
they break larger chemicals into smaller pieces, that than get broken down into individual componnets by the intestinal brush border enzymes.
_____ neutralizes the acidic chyme that enters the small intestine from the stomach.
what two things are necessary for efficient fat breakdown?
pancreatic juice and bile
absorption:
the process of moving substances from the lumen of the gut into the body
what prevents substances from moving between cells of the epithelia?
tight junctions join the epithelial cells of the intestinal mucosa.
how do materials pass through epithelial cells
enter its apical membrane and pass to the interstitial fluid on the other side of the cell.
what happens once material makes it to the interstitial fluid of a cell
substances diffuse into blood capillaries
from the capillary blood in the villus, substances are transported to the liver via the …
hepatic portal vein
lipid digestion is different because…
some lipid digestion products enter the lacteal in the villus to be carried via the lymphatic fluid to the blood.
nonpolar substances
lipid soluble
which substances can dissolve in the lipid core of the membrane and be absorbed passively through simple diffusion?
why.
nonpolar (lipid soluble) substances
because of the structure of the plasma membrane
how do substances (other than lipid soluble) get transported through the plasma cell membrane?
carrier mechanism
most nutrients are absorbed by active transport driven directly or indirectly (secondarily) by
metabolic energy (ATP)
enzymes:
digest small particles into components that can be absorbed.
what is proteins chemical monomer?
amino acids
what is carbohydrates chemical monomer?
monosaccarides
what is triglycerides (fats) monomer:
free fatty acids and monoglycerides
Pepsin is the only digestive enzyme that is maximally active at
acidic pH.
pepsin cleaves proteins into :
peptide fragments and small amount of individual amino acids
peptide:
a compound of two or more amino acids linked in a chain
what happens when chyme is neutralized in the duedenum?
pepsin is denatured
which organ supplies most of the enzymes used in digestion?
pancreas
exocrine part of the pancreas produces and secretes most of the digestive enzymes
neither amalyse or pepsin is required for digestion
pancreatic enzymes alone are sufficient
pancreatic lipase is essential for
what will happen without it?
fat digestion
malabsorption
which dietary component cannot be digested and absorbed by human?
cellulose:
a polysaccaride in fruits and vegetables.
dietary fiber
where is most of the water absorbed in the GI tract?
small intestine
salt and water may be absorbed through what 2 forms of transport?
trancellular: through intestinal epithelial cells
paracellular transport: through leaky tight junctions between cells.
which form of transport is passive and keeps the total osmolarity of intestinal contents to the osmolarity of blood plasma
paracellular transport
brush border enzymes:
enzymes located in the brush border (microvilli of small intestine) that break down starch and dissacarides
because
only monosacharides are absorbed
brush border:
microvilli of epithelial cells of the small intestine (apical surface)
what is the purpose of microvilli on epithelial cells in small intestine?
greatly increase surface area for absorption
after proteins, peptides from pepsin digestion, proteins from sloughed cells, and enzymes enter the small intestine for digestion these 4 things continue protein digestion in the lumen.
trypsin, chymotrypsin, caboxypeptidace, and major pancreatic proteases.
these enzymes are maximally active at pH 7.
what is the most abundant dietary fat?
triglycerides
triglycerides are made from:
a glycerol molecule and three attached fatty acids
(short, medium, or long chains of carbon and hydrogen)
what breaks down triglycerides?
pancreatic lipase
maximally active at pH7
which compound results in the emulsification of fats?
bile salts
which enzyme breaks down fat into the chemical building blocks?
lipase
since fat molecules are insoluble in water, they tend to aggregate in large drops, leaving little surface area of lipase to work.
what process is utilized to change this?
segmentation in the small intestine breaks the larger drops into smaller drops and disperses them throughout the chyme.
emulsification:
a process in which large lipid globules are broken down into several small lipid globules.
these small globules are widely distributed in the chyme rather than forming large aggregates
(shaking water and oil)
the function of bile is related to their function:
hydrophobic on one side, hydrophilic on the other side
most absorption of dietary nutrients occurs in the small intestine. which breakdown of products of digestion can cross the plasma membrane of small intestine epithelial cells by simple diffusion?
monoglycerides and free fatty acids
(nonpolar molecules that are lipid soluble)
triglycerides are reassembled inside of the cell and packaged into …
chylomicrons that are coated with lipoproteins to keep them emulsified
lipoproteins:
soluble proteins that combine with and transport fat or other lipids in the blood plasma
chylomicrons:
large triglyceride-rich lipoproteins produced in enterocytes from dietary lipids.
namely fatty acids and cholesterol
chylomicrons leave the cell by exocytosis. since they are too large to pass through the basement membrane of the capillaries, they enter lymph vessels called _____.
lacteals
what is the correct substrate for proteases?
proteins (or peptides)
what is the correct substrate for proteases?
proteins (or peptides)
which major process involves removing nutrients and water from the lumen of the GI tract and delivering them to blood or lymph?
absorption
most nutrients are absorbed into blood capillaries, and travel to the liver by way of the hepatic portal vein, most fats, however, are too large to be absorbed into blood capillaries and instead are absorbed into the larger _____.
lacteals
where does segmentation occur?
small intestine
(only organ who does this)
purpose is mixing food with enzymes and bringing it close to intestinal walls.
where does segmentation occur?
small intestine
(only organ who does this)
purpose is mixing food with enzymes and bringing it close to intestinal walls.
how would you classify chewing food?
mechanical breakdown
