Flashcards in Nutrient Absorption Deck (36):
What are the 2 forms of carbs?
-Monosaccharides (glucose, galactose, fructose)
-Disaccharides (Sucrose, lactose, maltose
-Starch (plant storage of glucose)
-Glycogen (animal storage of glucose)
Out of simple and complex carbs, which ones are readily absorbed?
-disaccharides, starch and glycogen all need chemical digestion before they can be absorbed
Are carbs digested in the mouth?
Yes, if carbs contain starch salivary amylase will start to turn it into maltose
Are carbs digested in the stomach?
no, salivary amylase is inactivated because of the stomach acid
Are carbs digested in the small intestine?
Yes, but the brush border enzymes
What are the brush border enzymes?
Lactase- lactose into glucose and glycogen
Sucrase- sucrose into glucose and fructose
Maltase-maltose into glucose and glucose
How are starch and glycogen digested into monosaccharides?
Amylase breaks them down to disaccharides and then brush border enzymes break them down into monosaccharides
How are glucose and galactose absorbed through the luminal side?
Trough Glucose/ galactose and Na symporter with Na concentration gradient
-because they have the same carbon configuration
How is fructose absorbed on the luminal side?
Fructose uniporter because it is a different carbon configuration and normally low levels in the body
How are sugars moved from the basolateral side to the interstitial fluid and then blood?
Moves through a monosaccharide (sugar) uniporter. Once in interstitial space, sugars diffuse into the capillaries
How do we maintain Na concentrations in the epithelial cells of small intestines?
Through Na/KATPase pump
What are sources of protein?
-different and same aminos for each group
What are essential amino acids?
Those that we require from food that our body can not make
Is there digestion of protein in the mouth?
No chemical because there are no enzymes but there is mechanical digestion due to chewing
Is there protein digestion in the stomach?
Yes, pepsin in the stomach breaks down polypeptides into smaller peptide strands
Is there protein digestion in the small intestine?
-Aminopeptidase and dipeptidase
-Pancreas secretion of trypsin, chymotrypsin, carboxypeptidase (all activated in small intestine)
What are exopeptidase?
Enzymes that cut one amino acid off either end of a polypeptide
-aminopeptidase and carboxypeptidase
What are endopeptidases?
Enzymes that cut polypeptides in the middle to form smaller peptides
How are di and tripeptides absorbed?
Enter through the luminal membrane via H/di and tripeptide symporter
-they either remain as di and tripeptides and exit via Na/di and tripeptide exchanger or they are broken down into single amino acids
How are single amino acids absorbed?
Enter through the luminal membrane via Na/AA symporter and exit through Na/AA exchanger
How are peptides absorbed?
Common in infants but through endo and exocytosis
What is a triglyceride?
glycerol backbone with 3 fatty acid chains
-chains do not have to be the same, can have different amount of carbon and can be saturated and unsaturated
Is there fat digestion in the mouth?
Yes, lingual lipase is present but does not work in the mouth
Is there fat digestion in the stomach?
Yes, this is where lingual lipase is activated due to the acidic environment.
-Gastric lipase is also there and ready
Is there fat digestion in the small intestine?
Yes, pancreatic lipase does the best job at digesting fat (with the help of collapse)
-liver secretes bile which also helps
What are chylomicrons?
Repacking of lipids within cells into carriers to allow for transport in the body
What are the functions of the lipases?
Within the fat droplet ball after mixing, they break down the triglyceride into di,mono and free fatty acids
What is the role of colipase?
Is able to move bile salts aside on the fat droplet in order to let lipase in and start breaking down the triglycerides
How are lipids absorbed?
When large lipid droplets are broken down via SI into smaller drops, the bile salts attach sound the outside. Colipase separates bile salts to allow pancreatic lipase to enter and break down triglycerides in the droplet. Once broken down into monoglycerides and fatty acid chains and if the micelles are close enough to the cell membranes, the fatty acids and monoglycerides diffuse into the cell, and are repacked by the smooth ER into chylomicrons in which those are leased into the lymphatic vessels
What are chylomicrons?
Reformed balls of fatty acids and monoglycerides in the cell by smooth ER.
-transportation form of the lipids to other cells and throughout the body
What makes a chylomicron different from a micelle?
Chylomicrons are protected with a protein shell
Micelles have bile salts surrounding the outside
How to chylomicrons exit the cell and enter the lymph?
Exit via exocytosis
Enter via pores
What are the fat soluble vitamins?
What are the water soluble vitamins?
How to water soluble vitamins enter the cell?
Through transporters on the cell membrane in order to bring them in