Digestion And Absorption Flashcards
Where are carbs digested?
In the intestinal lumen
How are carbs broken down for digestion in the mucosal lining of the duodenum and jejunum?
Glycosidase breaks down polypeptides
Isomaltase cleaves the a1-6C bond
maltase cleaves the a1-4C bond
Sucrase cleaves the a1-2C bond
Lactase cleaves the b1-4C bond
How are polysaccharides broken down in the mouth?
The 1-4 carbon bond of amylose is broken apart by salivary amylase into a short polysaccharide and maltose
Where are glucose, galactose, and fructose absorbed after digestion?
Through enterocytes into the bloodstream
How are galactose and glucose absorbed?
- Both are absorbed via active transport by the sodium glucose cotransporter protein (SGLT-1)
- SGLT-1 trades off 2 potassium for 2 sodium
- This process creates a high intracellular concentration of glucose
- The cell swells
- GLUT-2 pumps glucose out of the cell into the bloodstream
How is fructose absorbed?
- Fructose is absorbed via facilitated diffusion using GLUT-5 and transferred to the apical membrane
- Fructose then enters the cytosol of enterocytes
- Ketohexokinase phosphorylates fructose into fructose 1-phosphate
- Fructose 1-phosphate is released into the basolateral membrane of the blood vessel by GLUT-2
What happens to the body is there is a deficiency in disaccharides in the diet?
This can cause the passage of carbs into the large intestine which then draws water from the mucosa-osmosis cycle causing diarrhea
This reduces nutrient absorption
Causes polyphagia and weight loss
Also called exocrine pancreatic insufficiency
What is CSID?
Similar to EPI
It is an autosomal recessive disorder
Caused by an intolerance to ingested sucrose and causes bacterial fermentation
How are carbs metabolized by alloenzymatic eaters?
Carbs are metabolized by microbes
Turn the polysaccharides into acetate, butyrate, and propionate and excrete VFAs, CO2, and methane gas
What is cross-feeding?
Where the end products of one bacterial colony becomes the substrate for another
How is starch degraded in the rumen?
By amylolytic bacteria
What does it mean if chickens and ducks are precocial?
They have fully developed enzymes to degrade carbs at birth
What does it mean if a parrot or pelican are altricial?
They consume crop milk to get enzymes to degrade carbs
How do young mammals degrade carbs?
They rely on lactate from the mother
Develop specific enzymes with introduction to feedstuffs
