[Physiology] Nutrient digestion and absorption Flashcards
Principal dietary constituents
Carbohydrate
Protein
Fat
Vitamins
Minerals
Water
Monosaccharides
Hexose sugars (6C)
Breakdown products of complex CHOs which are absorbed by small intestine only
Hexose sugars (6C)
glucose, galactose, fructose
Disaccharides
Two monosaccharides linked together by glycosidic bond
how are disaccarides broken down
Broken down to constituent monomers by brush border enzymes in small intestine (enterocytes in epithelial cells, in apical membrane)
what are the components of lactose
glucose + galactose (lactase)
what are the components of sucrose
glucose + fructose (sucrase)
what are the components of maltose
glucose + glucose (maltase)
what is starch
plant storage form of glucose
what are the two glucose components in starch
a-amylose, amylopectin
a-amylose
glucose linked in straight chains
amylopectin
glucose chains highly branched
what are glucose monomers linked by
α-1,4 glycosidic bonds
what are α-1,4 glycosidic bonds hydrolysed by
amylases (saliva, pancreas)
what is cellulose
constituent of plant cell walls
what are the components that make up cellulose
linear chains of glucose monomers linked by β-1,4 glycosidic bonds
Dietary fibre
what can the dietary fibre in cellulose be digested by
no enzymatic digestion in vertebrates - require bacteria
what is glycogen
animal storage form of glucose
what is glycogen made up of
Glucose monomers linked by α-1,4 glycosidic bonds
what are the two membranes
apical membrane
basolateral membrane
what are the apical membrane and basolateral membrane separated by
tight junction space complex
transcellular transport
vesicle-mediated transport of macromolecules, such as plasma proteins, across the endothelial barrier
paracellular
transfer of substances across an epithelium by passing through the intercellular space between the cells
vectorial transport
The transport of an ion or molecule across an epithelium in only one direction (e.g. absorption of nutrients in the gut). Vectorial transport requires that transport proteins are nonrandomly distributed between the apical and basolateral plasma membrane.
when starch/glycogen is broken down by amylase what is it broken down into
maltose, sucrose, lactose
how does Na and glucose enter the apical membrane
SGLT1 transporter
how does glucose enter the cell following transport by SGLT1
GLUT-2 transporter
how does sodium leave the cell following entry by SGLT1
sodium - potassium ATPase
how does fructose enter the apical membrane
GLUT-5 transporter
how does fructose go out the basolateral membrane following GLUT-5 entry
GLUT-2
what do all three sugars leave the cell using
GLUT-2
what transporter does glucose and galactose use for entry into the apical membrane
SGLT1
what is a protein
Polymers of amino acids linked together by peptide bonds
how does the chain length vary on different proteins
large variation of chain length
what is often undergone by proteins
post translational modification
what is an example of post translational modification for a protein
(addition of CHO = glycoprotein; lipid = lipoprotein)
what are peptides
Small proteins, 3-10 amino acids in length
what are proteases/peptidases
Enzymes which hydrolyse peptide bonds and reduce proteins or peptides to amino acids
endopeptidases
acts on the on the interior amino acids within the protein, not on the terminal ones. - used in water hydrolysis
exopeptidases
exopeptidase is any peptidase that catalyzes the cleavage of the terminal (or the penultimate) peptide bond
what are the two types of exopeptidases
aminopeptidase
carboxypeptidase
aminopeptidase
Aminopeptidases catalyze the cleavage of amino acids from the amino terminus of protein or peptide substrates
carboxypeptidase
protease enzyme that hydrolyzes a peptide bond at the carboxy-terminal end of a protein or peptide
how does an amino acid enter the apical membrane
enters alongside sodium on SAAT1
how does an amino acid leave basolateral membrane
independent of sodium
sodium leaves via sodium potassium ATPase
