Biochem - macronutrients digestions Flashcards
bonds in proteins? in fats?
proteins have peptide bonds
fats have ester bonds
class of enzymes that perform hydrolysis?
hydrolases
2 main disaccharides in diet?
lactose and sucrose
lactose =
galactose + glucose
sucrose =
fructose + glucose
starch
polysaccharides of glucose; contains amylose and amylopectin
amylose
spiral chain, unbranched, alpha 1,4 linked starch components
amylopectin
branched polymer of starch with alpha 1,4 chains and 1,6 branches; similar to glycogen
what enzyme works in mouth? what does it do?
salivary alpha amylase
cleaves starch by breaking the 1,4 linkages between glucose –> this creates dextrins
dextrins
linear and branched oligosaccharides that enter stomach after salivary amylase cleaves starch
digestion that started in the stomach is continued …
in the intestines by pancreatic alpha amylase
salivary and pancreatic alpha amylases are…
both endo-glucosidases found in the brush border
intestinal absorption : aa vs fats
aa absorbed by villi and enter portal vein –> liver
fats dont go through portal vein - they go into lymph as chylomicrons
what neutralizes stomach acid in the small intestine
bicarbonate from the pancreas
products of pancreatic alpha amylase on glucose
disaccharides maltose and isomaltose, trisaccharides, and small oligosaccharides
what is digested at brush border?
sucrose, lactose, and starch products
4 brush border enzymes…
hydrolyze di, tri, and oligo saccharides into monosaccharides
glucoamylase
isomaltase
sucrase
lactase
glucoamylase
also called alpha glucosidase
cleaves glucose from nonreducing ends of oligosaccharides
sucrase
converts sucrose into glucose and fructose
lactase
also called beta galactosidase
cleaves lactose into galactose and glucose
transport in intestines
glucose and Na+ are transported by secondary active transport
B-galactosidase deficiency
lactase deficiency
lactose cannot be digested and is oxidized instead by gut bacteria which produces gas and causes bloating and watery diarrhea due to increased osmotic pressure
-common in asians
dietary fiber
carbs that cannot be digested
=cellulose, carragennan, raffinose, lignin, hemicelluloses
cellulose
dietary fiber
B 1,4 linked glucose - cannot be cleaved by human enzymes
raffinose =
sucrose + galactose
trisaccharide in beans, cause gas
BEANO
alpha glucosidase breaks the B1,4 linkage in raffinose/trisaccharide in beans
fate of indigestible food…
fermentation by colon bacteria producing
- lactic acid, short chain FAs, and gases (H2, CO2, and CH4)
- osmotic effect –> watery stool
- malabsorption
protein digestion pathway
starts in stomach – pepsin converts proteins to smaller polypeptides – in small intestine proteolytic enzymes from the pancreas cleave polypeptides into oligopeptides and AA – intestinal enzymes cleave the oligopeptides into AA –finally AA are absorbed by epithelium into blood
proteolytic enzymes made by pancreas
trypsin, chymotrypsin, elastase, and carboxypeptidases
proteolytic enzymes made by intestinal epithelium
aminopeptidases, dipeptidases, and tripeptidases
inactive form of enzyme
zymogen
how to activate a zymogen?
remove a peptide fragment
functions of stomach low pH
kills bacteria and denatures proteins so that pepsin can cleave them into oligopeptides
pepsin
made by chief cells as the inactive pepsinogen
HCL in stomach is secreted by parietal cells
HCl cleaves pepsinogen to pepsin
parietal cells make?
chief cells make?
HCl
pepsinogen
bicarbonate role in intestines
secreted by pancreas to neutralizes stomach pH so that enzymes can act
endopeptidases vs exopeptidases
endo (trypsin, chymotrypsin, and elastase) cleaves peptide bonds in the middle of a chain
exo (carboxypeptidase A and B) cleave one at a time, peptide bonds at the ends of chain
trypsinogen –> trypsin
by enteropeptidase
trypsin can also begin to cleave other trypsinogen and all other zymogens
which enzyme can cleave all other zymogens and itself
trypsin
chymotrypsinogen and proelastase
cleaved by trypsin into chymotrypsin and elastase
procarboxypeptidases
cleaved by trypsin into carboxypeptidase A and B
proteases made by epithelial cells in intestines
finish conversion of proteins into aa amino peptidases (one at a time) and di and tri peptidases
sodium-aa carrier system
secondary active transport via atp hydrolysis of Na up its gradient into blood and aa travels down its gradient into blood
passive (facilitative )absorption of monosaccharides and aa
GLUT transporters do not use ATP
glucose needs transporter because it is water soluble and cannot cross lipid bilayer
GLUT
passive transporters; dont use ATP
SGLT1 and 2
sodium-glucose linked transporters – active transport
secondary active NA-KATPase
1 is in intestines and kidney
2 is in kidney
SGLT1 transports—
GLUT 5 transports…
GLUT2 transports…
sglt1 = glucose and galactose
glut5 = fructose
INTO enterocytes
glut2 transports glucose, fructose, and galactose from enterocyte into blood
enzyme to break down fat?
pancreatic lipase
fat digestion
begins in small intestine by pancreatic lipase which turns triacylglyceral into 2-monoacylglycerols and free FA –> packages into micelles
gallbladder role in fat metabolism
gallbladder releases bile (bile salts and acids) to emulsify fats
bile
made by liver and stored by gallbladder
used to emulsify fats
bile salts are..
recycled; only 5% are excreted in poop which is the only way to get rid of cholesterols
cmc
critical micelle concentration
minimum concentration at which a micelle will form
lechitin is a
phospholipid (phosphatidylcholine)
used with bile salts to emulsify
