10 carb absorption Flashcards
Can the small intestine absorb polysaccharides?
nope, only monosaccharides
What does startch contain?
amylose - straight chain polymer (alpha-1,4 linkages)
amylopectin - branched (alpha-1,4 and alpha-1,6 linkages)
How does glycogen compare to startch?
its like a more branched version of amylopectin
What is lactose, maltose, and sucrose?
lactose = glucose + galactose maltose = glucose + glucose sucrose = glucose = fructose
What are the 2 main stages of dietary carbohydrates?
intraluminal hydrolysis
membrane hydrolysis
What is salivary amylase inactivated by?
gastric acid
What induces the release of pancreatic amylase?
CCK
What does amylase hydrolyse?
internal alpha-1,4 linkages
What does amylase NOT hydrolyse?
terminal alpha-1,4 linkages
alpha-1,4 linkages adjacent to alpha-1,6 linkages
alpha-1,6 linkages
What are the products of amylase activity?
maltose (ultimately) and alpha-limit dextrins which the alpha-1,6 linkages
What happens roughly in membrane digestion?
hydrolysis of oligosaccharides to monosaccharides by brush-border disaccharides
What are the 3 brush border disaccharidases, and what linkages must they hydrolyse?
galactase
maltase
sucrase isomaltase
(alpha-1,4 linkages, although the isomaltase is the only one able to split alpha-1,6 linkages of alpha-limit dextrins)
How are glucose and galactose absorbed?
SGLT1 transporter, energy provided by Na chemical gradient
How is fructose absorbed?
GLUT5 transporter
How do glucose, galactose, and fructose exit the basal end of the cell?
GLUT2 transporter
