98. CHEMICAL CHANGES IN CARBOHYDRATE DIGESTION AND 

 ABSORPTION: MAN, LABORATORY MAMMALS 



Carbohydrate digestion Is the enzymatic hydrolysis of poly- and oligosaccharides Into their monosac- 

 charide components which are then absorbed into the blood stream. Monosaccharides are phosphorylated 

 to hexose-6-P047 as they enter the intestinal mucOBa and then dephosphorylated before they enter the 

 blood stream. 



A = Salivary amylase (ptyalin); B = Pancreatic amylase (amylopsln); C = Maltase; D = Sucrase ( inver- 

 tase); E = Lactase 



CAR BOHYDRATE 1 



Polysaccharides^ 



Soluble Starch 



Erythrodextrins 



Achrodextrins 



B B' 



Oligosaccharides 3 



Monosaccharides'* 



C''. D^, e9 



^ 



Maltose 



Galactose 



^ 



Fructose 



-i— C7 »• 



10 



Glucose 



lOy 



ATP 



Hexose 

 Phosphates 



/l/ Ingested. /2/ Polysaccharides Including glycogen, starch dextrlns and cellulose are made up of many 

 monosaccharide (simple sugar) molecules. Cellulose, although made up of glucose molecules is not digest- 

 ible by mammals. /?/ Oligosaccharides are carbohydrates con^iosed of only a few (down to two in the case of 

 dieacchftrides) molecules of monosaccharide. Sucrose contains glucose and fructose; maltose is congjosed of 

 two molecules of glucose; and lactose contains glucose and galactose as constituents, /k/ Ingested mono- 

 saccharides are absorbed into the blood stream without breakdown. /5/ Salivary amylase not only converts 

 polysaccharides to soluble starch, etc., but also breaks off some maltose. /6/ Pancreatic amylase, but not 

 salivary amylase, will hydrolyze uncooked starch only to an insignificant extent. /?/ Maltase, in Intes- 

 tinal secretion, hydrolyzes each molecule of maltose to two molecules of glucose. /8/ Sucrase, in intes- 

 tinal secretion, hydrolyzes sucrose to glucose and fructose. /9/ Lactase, in intestinal secretion, hydro- 

 lyzes lactose to glucose and galactose. /lO/ Possibly other hexoses. 



178 



