protein and carb digestion Flashcards
digestion and absorption of carbohydrates
mouth and small intestine
digestion and absorption of proteins
stomach and small intestine
digestion and absorption of fats
small intestine
why does absorption occur at a rapid rate as a result of
extensive folding in intestinal mucosa called plicae circulares, villi and microvilli
t/f small intestine has a large surface area for both digestion and absorption
true
Epithelial cells of the small intestine produce membrane-associated digestive enzymes, which are
brush border enzymes = enterokinase
sucrase
maltase
lactase
enterokinase is required for
activation of trypsin
trypsin
digestive enzyme of proteins
sucrase
maltase
lactase are responsible for
splitting disaccharides
brush birder enzymes are not secreted into the
lumen
brush enzymes are found in
attached to the cell membrane of microvilli in small intestine
types of polysaccharides
starch
cellulose - plant fibers
glycogens - animal starch
types of starch
amylose
amylopectin
types of disaccharides
maltose = glucose + glucose
sucrose = fructose + glucose
lactose = galactose + glucose
in starch, glucose units are bounded by
alpha 1-4 linkages
in cellulose, glucose units are bounded by
beta 1-4 linkages
enzyme that breaks cellulose
cellulase
similar to cellulose
quitin
animal starch
glycogens
only found in plants
sucrose
only found in milk
lactose
only found in germinating seeds
maltose
2 sites of carb digestion:
- saliva ptyalin
- pancreatic amylase in small intestine
2 phases of carbohydrate absorption
luminal phase digestion
membranous phase digestion
monosaccharides transporters/absorbers
are in enterocytes
involved in small intetsine absorption of
d-glucose
d-galactose
d-fructose
enterocytes have 2 types of monosaccharide transporters/absorbers
luminal membrane
brush border membrane
basolateral membrane
monosaccharide transporters in luminal membrane
SGLT1
GLUT 5
Whic monosaccharide transporter can be found in luminal membrane and basolateral membrane
GLUT5
SGLT1 and GLUT2 transports and absorbs
glucose
galactose
GLUT 5 transports and absorbs
fructose
where are proteins digested?
stomach and small intestine
pancreatic proteases break proteins into
tri and di peptides
single amino acids
for protein digestion, IN THE STOMACH what has to happen to gastric pepsinogen
has to be activated by HCl to pepsin
how are peptides linkages broken?
hydrolisis
protein digestion in the small intestine is mediated by
pancreatic enzymes
name pancreatic enzymes that play a role in protein digestion in the small intestine
trypsin
chymotrypsin
carboxypolypeptidase
elastase
in the stomach, pepsin turns proteins into
proteoses, peptones,polypeptides
in the small intestine, peptidases, turn polypeptides and amino acids into
amino acids
proteins are broken first into_____in the stomach and then into_____ in the small intestines
plypeptides
amino acids
pancreatic enzyme activation
trypsinogen is activated by enterokinase and turned into trypsin
trypsin will activate
zymogens
name the active zymes of the following zymogens
chymotrypsinogen
proelastase
procarboxypeptidase A
procarbopeptidase B
chymotrypsin
elastase
carboxypeptidase A
carboxypeptidase B
pancreas derived enzymes for protein digestion
trypsin
chymotrypsin
carboxypeptidase
elastase
Trypsin and chymotrypsin cleave
peptide bonds
carboxypolypeptidase cleaves
individual amino acids off the carboxyl end of the polypeptide
elastase attacks
elastin fibers
Brush border enzymes for protein digestion
Aminopolypeptidase
dipeptidases
brush border enzymes are in the
microvilli of the eneterocyte looking inside the LUMEN
aminopeptidases and dipeptides split
the remaining polypeptides into di- and tri-peptides and a few amino acids. These two peptidases also facilitate peptide movement into the enterocyte
onece inside the cell, specific di or tir peptidases in cytoplams
disassemble the remaining peptides into individual amino acids which move across the cell and pass into the blood.
order or enzymes that digest proteins in small intestine
pancreas derived enzymes - in lumen of small intestine
brush border enzymes - in microvilli looking into lumen of small intestine
specific di or ti peptidases in cytoplasm inside enterocyte
Absorption of free single amino acids in enterocytes by
co-transport with Na+
Absorption of di- and tri-peptides in enterocytes by
co-transport with H+ ions (proton) via a transporter called PepT1
The basolateral membrane of the enterocyte contains additional transporters which export amino acids from the cell into
blood
basolateral membrane of enterocytes transporters are not dependent on
Na gradient
t/f Newborn babies appear to be capable of absorbing a substantial amount of undigested proteins, hence they can absorb antibodies( γ-globulins: IgG, IgA and IgM) from colostrum- their mother’s first milk;
true
t/f In adults, only the free amino acids enter the portal vein.
true
causes botulism
This protein is resistant to digestion and is thus intact when it is absorbed into the blood.
protein botox
which 2 proteins can be absorbed without being digested?
immunoglobulins
botox
Triglycerides (such as fat and oil),
Phospholipids (such as lecithin),
Sterols (such as cholesterol),
lipids
what enzymes hydrolises fats
lipase
The salivary glands and stomach of neonates (newborns) produce
lipases
where does fat digestion occur MAINLY
small intestine by pancreatic lipase
lipase is originated from the
PANCREAS
LIPASE digests fats into
two FFAs (free fatty acids) + one 2-monoglyceride
The arrival of lipids (primarily triglyceride, or fat) in the duodenum serves as a stimulus for
secretion of bile from the liver.
emulsification
bile salts are secreted into duodenum and act to break up the fat droplets into emulsified droplets = micelles
The emulsification of lipid aids digestion because the smaller and more numerous emulsification droplets present
great surface area
fat digestion occurs at the surface of the
emulsified droplets and colipase coats the emulsified droplets and lipase anchors there to digest
Pancreatic enzyme cholesterol ester hydrolase digest
Cholesteryl esters = dietary lipid
Pancreatic enzymes PLA2 can hydrolyze
phospholipids = FAA +lysophospholipids
lipid absorption occur when
Free fatty acid, monoglyceride and lysophospholipid can leave the micelles and enter enterocytes by p[assing through the microvilli
difference between absorption of amino acids + monosaccharides and free fatty acids inside the enterocyte
amino acids+ monosaccharides are not modified
free fatty acid, monoglyceride and lysophospholipids resynthesize triglycerides and phospholipids
Triglycerides, phospholipids, and cholesterol are then combined with protein (apoprotein) inside the enterocytes to form small particles called
chylomicrons
chylomicrons are going to be secreted into
central lacteals (lymphatic capillaries) of the intestinal villi.
absorbed lipids pass through the
lymphatic system entering the thoracic duct and going into the thoracic duct to venous blood
absorbed amino acids and monosaccharides enter the
hepatic portal vein
chylomicrons in blood are removed by which enzyme
lipoprotein lipase attached to endothelium of blood vessels
lipoprotein lipase attached to endothelium of blood vessels will hydrolize triglycerides into
FFA and glycerol for use for cells
the remnant particles of chylomicrons containing cholesterol are
taken up by liver by endocytosis
the protein part of the remnant part has the receptors
Cholesterol and triglycerides produced by the liver are combined with other apoproteins and secreted into the blood as
very-low-density lipoproteins (VLDLs) during fasting during fasting
very-low-density lipoproteins (VLDLs) are turned into
low-density lipoproteins (LDLs)
low-density lipoproteins (LDLs) and are in charge of transporting
cholesterol to organs
high cholesterol causes
atherosclerosis
excess cholesterol is returned to from organs to liver attached
to high-density lipoproteins (HDLs) and protects
to high-density lipoproteins (HDLs) and protects
against atherosclerosis
