Carb metabolism (1.6) Flashcards
What carb does the body want as fuel?
Glucose
What carb(s) do people eat?
NOT glucose
I know this is a copout, but there are more slides coming…
What monosaccharide do people usually eat?
Fructose
What are the disaccharides people usually eat?
Lactose
Sucrose
Maltose
Isomaltose
What enzyme breaks down lactose? What are the products? Where is it most active?
Lactase domain of beta-glycosidase (splits the α1,4 bond )
Forms Galactose and Glucose
Most active in the jejunem
What happens if someone is lactose intolerant (no lactase)?
Bacteria ferment lactose to lactic acid –> water floods in to balance pH –> diarrhea
What enzyme complex breaks down both sucrose and isomaltose? What are the products? Where is it most active?
Sucrase/Isolmaltase complex (S- cleaves α1,2 bonds; I- cleaves α1,6 bonds)
S- Fructose and Glucose
I- Glucose x2
Most active in the jejunem
What enzyme breaks down maltose? What are the products? What else can it do? Where is it most active?
Glucoamylase/maltase (cleaves α1,4 bonds) [exoglycosidase]
Glucose x2
cleaves glucose off non-reducing ends of starch
Most active in the ileum
What are the starches people eat?
Amylose (α1,4 bonds)
Amylopectin (α1,4 bonds AND α1,6 bonds)
What breaks down starch? What are the products? Where is it most active?
Amylase (cleaves α1,4 bonds) [endoglycosidase]
Polysaccharides 4-9 residues long…often maltose
Most active in the duodenum
What is an easy way to remember which enzyme is most active in which site?
Purely starch breakdown (duodenum…has to be broken down to smaller first)
Purely disaccharide breakdown (jejunem…get the bulk of the carbs out)
Mix of starch and disaccharide breakdown (ileum…take care of what’s left from the initial starch breakdown)
What co-transports with carbs into intestinal epithelial cells when they have to go up their gradient?
Na+…same as usual…there is a Na/K pump on basolateral side
