Nutrient Digestion and Absorption Flashcards
what form can the body absorb carbohydrates in?
hexose sugars
what are the hexose sugars?
glucose, galactose, fructose
what are disaccharides made up of and what links them?
two monosaccharides linked together by a glycosidic bond
where are the enzymes which break down disaccharides?
brush border of small intestine
what is lactose made up of?
glucose + galactose
what is sucrose made up of?
glucose + fructose
what is maltose made up of?
glucose + glucose
which polysaccharide cannot be enzymaticallly digested by vertebrates?
cellulose
how do vertebrates digest cellulose?
bacterial production of cellulose
what form do plants store glucose in?
starch
what form does a-amylose take?
glucose linked in straight chains
what form does amylopectin take?
highly branched glucose chains
what type of bond links glucose monomers in starch and glycogen?
a-1,4-glycosidic bond
what is the animal storage form of glucose?
glycogen
which enzyme is required to break down b-1,4-glycosidic bonds?
cellulase
which enzyme is required to break down a-1,4-glycosidic bonds?
amylase
what separates the apical membrane of columnar cells from the basolateral membrane?
tight junctions
what is a normal blood glucose level?
5mM
which transporter allows glucose to cross the apical membrane?
SGLT1 –> sodium coupled glucose transporter
which transporter allows glucose to cross the basolateral membrane?
GLUT-2
which transporter allows fructose to cross the apical membrane?
GLUT-5
which transporter allows fructose to cross the basolateral membrane?
GLUT-2 (same as glucose)
structurally, what are proteins?
polymers of amino acids linked together by peptide bonds
what are small proteins of 3-10 amino acids in length known as?
peptides
which enzymes are required to hydrolyse peptide bonds?
proteases or peptidases
how do endopeptidases act?
act in the middle of the chain, splitting into two smaller peptides.. etc
how do exopeptidases act?
act near the amino-terminal or carboxy-terminal ends to shorten the chain
which transporter allows amino acids to cross the apical membrane?
SAAT1 –> sodium coupled amino acid transporter
what causes the acidic microclimate close to the apical membrane?
NHE3 –> sodium hydrogen exchange - creates high conc of hydrogen ions on the surface
why is it beneficial to have an acidic microclimate near the apical membrane?
PepT1 transporter transports dipeptide with a hydrogen ion across the apical membrane
