Carbohydrate Digestion Flashcards
Digestion
Primary site is intestinal lumen, catalyzed by glycosidases
Salivary Amylase
Break α(1-4) bonds during mastication. Inactivated with high stomach acidity.
Pancreatic Amylase
Continue carbohydrate digestion when bicarbonate ,from the pancreas, neutralizes acids.
Intestinal Digestion
In mucosal lining of duodenum &
upper jejunum catalyzed by disaccharidases
& oligosaccharidases
Isomaltase
Cleaves α(1-6) bond in isomaltose, producing glucose
Maltase
Cleaves the α(1-4) bond in maltose, producing glucose
Sucrase
Cleaves α(1-2) bond in sucrose, producing fructose & glucose
Lactase
Cleaves β(1-4) bond in lactose, producing galactose & glucose
Galactose and Glucose absorption
Absorbed into enterocytes along brush boarder by active transport through SGLT1 (Na+/K+ ATPase pump) which increases intracellular concentrations. Leak out GLUT2 into circulation.
Fructose Absorption
Absorbed into enterocytes along brush boarder by facilitated diffusion through GLUT5. Converts to fructose 1-phosphate (via Ketohexokinase) and released into circulation via GLUT2.
Disaccharide deficiency
Carbohydrates not absorbed in small intestine and make it to large which draws water from mucosa into large intestine, causing osmotic diarrhea.
Exocrine pancreatic insufficiency (EPI)
Decrease pancreatic enzymes leading to polyphagia, weight loss & large volume of loose stools
Lactose Intolerance
After weaning. cats and dogs stop producing lactase. Undigested lactose draws water into intestine, results in diarrhea
Congenital sucrase-isomaltase deficiency (CSID)
Autosomal recessive disorder in Japanese shrew causing intolerance to sucrose.
Rumen Digestion
Breakdown carbs to VFAs, gas, microbial cell mass and heat. Some ingested by microbes directly.
Fungi role
Penetrate cell wall of plants, begin enzymatic digestion and provide entrance area for bacteria to break down cellulose
Cross Feeding
Feed microbes to feed cow. End products of one organism are substrates for another
Rumen Fermentation of Starch
Degraded by amylolytic bacteria. Helps to process grains to decrease particle size and increase surface area.
Methane Production
Cattle responsible for ~9.5% of greenhouse gasses. Cellulose fermentation increase methane production (grass fed beef)
Precocial
Born self-sufficient. Some birds have full development of carbohydrate digestive enzymes at birth
Altricial
Born in helpless condition. The birds that require crop milk or young mammals rely on lactose for mom’s milk and develop other enzymes with slow introduction of solid food.
