CARBS Digestion and Absorption Flashcards
Where digestion begins in earnest
duodenum (first section of small intestine)
The mixture for digestion can be any osmolality in these three regions. Where does the luminal contents need to be isosmotic to plasma?
- oral cavity
- esophagus
- stomach
starting in the DUODENUM
Which organ contains a larger number of microorganisms?
Large intestine (stomach and small intestinal lumen are relatively free of them)
amylose
alpha-1,4 glycosidic linkage
amylopectin
alpha-1,4 and alpha-1,6 glycosidic linakeges
The human pancreas and salivary glands only secrete which enzyme for digestion and absorption of carbs? What linkages does it cleave? Where is it secreted and specifically where is it NOT secreted?
alpha-amylase, secreted into the lumen of the intestine and NOT into the blood
The two components of starch
amylose and amylopectin (70-80% of structure)
Where does digestion start?
In the mouth! Salivary gland amylase initiates
What in the stomach inactivates salivary gladn amylase?
Acid pH
Function of pancreatic amylase
hydrolyzes alpha-1,4 bonds to make small oligos, disacchs, and some monosacchs
Enzyme responsible for producing monosaccharides
Brush border glycosidases
What absorb monosaccharides? What are the transporters?
Intestinal epithelial cells: SLGT1, GLUT-5
What happens to nondigestable complex carbs?
Partially fermented by microorganisms. The short chain free FAs resulting can be used by epithelial cells to make ATP
Byproduct of the fermenation process
Methane–gets eliminated along with the non-digestible complex carbs (fiber)
What are the two main ectoenzymes the intestinal epithelial cells make and secrete?
Lactase and sucrase
What does SLGT1 in the absorptive epithelium transport?
Everything except fructose
Glut-5:
- Transports _____
- active/not active transporters
- Absorption capacity
- fructose (think 5=five=fructose=F)
- not active
- incomplete-50%
SLGT1
- Transports ____
- Active/not active transporter
- Reabsorption capacity
- Na-linked glucose/galactose transporter
- Active transporter: Energy for transportation from Na/K ATPase on basolateral side.
- High capacity and can absorb ~100%
If you ingest equal amounts of glucose and fructose, which will have a higher plasma level?
Glucose will be higher since fructose absorption is not complete.
Glut-2
- Transports ____
- Location
- passive/active
- paracellular reabsorption
- osmolality
- galactose/glucose + fructose
- basolateral side
- can only transport DOWNHILL (diffusion)
- Cl
- isosmotic
Role of lactase
Lactose –> Glucose + Galactose
Sucrase
Sucrose –> Glucose + Fructose
Maltase
Maltose –> Glucose + Glucose
If you wanted to lose weight, would you eat fructose or glucose?
Fructose
What is the rate of digestion of brown starches? Explain why
The rate of digestion is slow and digestion and absorption occur over a longer distance of GI tract.
What is they glycemic index? Compare glycemic index of amylose and oatmeal.
Glycemix index measures plasma glucose (y axis) vs. time. Oatmeal has a LOW index and over time has a much smaller peak than amylose. This is because it remains in the system longer. Feel full longer. Oatmeal rocks!
After amylose sharply rises in the glycemix index graph, it drops quickly. What is the cause of this?
Insulin is released due to high blood sugar.
What has the lowest glycemic index?
Fructose –30% (oatmeal is 67%)
Cellulose, hemicellulose, xylans, pectin, and gums are all examples of what?
Non digestible starches = fiber
-made of plant cell wall materials, we lack enzyme to respond
Where do enterocytes in small intestine get nutrition from?
Ingested amino acids
3 advantages of eating fiber
- gut stays full–requires bulk, motility stimulated by contents
- keeps microflora happy–they digest and yield short chain fatty acids (which feed the colonocytes). methane and hydrogen are eliminated
- absorbs certain toxins (cholesterol)
Why can short (
Transporters are in absorptive cells in small and large intestine so these shorter FAs can be absorbed along most of the GI tract and reach the portal vein (to liver).
NB: liver secretes bile which is usually essential for lipid digestion and absorption. The liver screens and filters molecules absorbed by GI tract
