Nutrient Digestion & Absorption Flashcards
What are the different Absorptive Mechanisms of Absorption?
1) Passive Diffusion
2) Facilitated Diffusion
3) Active Transport
4) Co-Transport
What occurs during Carbohydrate Digestion?
1) Salivary Amylase & Pancreatic Enzymes break complex carbs into Di-/Trisaccharides
2) Brush Border Enzymes break Disacchs into Monosacchs
What are examples of Brush Border Enzymes?
1) Maltase [Maltose -> 2x Glc]
2) Sucrase [Sucrose -> Glc-Frc]
3) Lactase [Lactose -> Glc-Gal]
What occurs during CHO Absorption Pt.1?
1) Intestinal Epithelial cells absorb Monosacchs by FacDiff & Cotransport
2) FacDiff always occurs down Conc. Grad
3) Cotransport can move molecule against ConcGrad
4) Both involve a carrier protein
What occurs during CHO Absorption Pt.2?
1) Cotransport of Glc reqs Na+ to enter cell
2) From epithelial cells, diffuse through cytoplasm -> Interstitial fluid -> capillaries
3) Transported to Liver via Hepatic Portal Vein
4) Once in the Liver, Gal & Frc can be converted into Glc
What occurs during Lipid Digestion & Absorption?
1) Lingual, Gastric, and Pancreatic Lipase breaks off two fatty acids leaving monoglycerides
2) Bile aids process by emulsifying lipids & aiding formation of micelles
3) Intestinal cells form new triglycerides that are coated with proteins creating chylomicrons which diffuse into interstitial fluid
4) From lacteals, chylomicrons proceed through the Lymph System and enter the bloodstream via the Thoracic Duct and Left Subclavian Vein
What occurs during Protein Digestion?
1) Tertiary structure disrupted via mechanical process & chem processing
2) HCl activates Pepsin, breaking peptide bonds
3) Pancreatic proteases break specific peptide bonds in polypeptides creating smaller peptides in the Small Intestine
What are two examples of Protein Enyzmes?
1) Carboxypeptidase [Sm. Intestine] breaks off terminal AA’s of peptide chain creating free AA’s
2) Dipeptidases from the Brush boarder break short peptide chains into individual AA’s
What occurs during Protein Absorption?
1) Individual AA’s are absorbed via FacDiff and Cotransport [some also “Active Transport”]
2) Diffuse from Epithelial Cells into Capillaries and transported to the Liver via HPV
What occurs during Water Absorption?
1) Cells do not actively absorb or secrete water
2) Water movement occurs via osmosis
3) Intestinal epithelial cells continuously absorb nutrients and ions
4) As a result, solute conc. drops towards the end of Sm. Intestine and into the Large Intestine
5) As a result, water is reabsorbed to maintain Os. Pressure
What occurs during Ion & Vitamin Absorption?
1) Regulated by Hormones [e.g. Aldosterone & Calcitriol] as well as existing tissue and fluid concentrations
2) Transport mechanisms include Cotransport, Active Transport, FacDiff, Simple Diffusion
3) Location varies by type and need
What is Gastrin?
Digestive Hormone that:
1) Stimulates release of Gastric Acids & Enzymes
2) Increases Motility
3) Released when foods enters the stomach
What is Cholecystokinin?
Digestive Hormone that:
1) Stimulates release of Pancreatic Enzymes, contraction, and emptying of Cholecyst
2) Relaxes Hepatopancreatic Sphincter
3) Inhibits Gastric Secretion
4) May reduce Hunger
What is Secretin?
Digestive Hormone that:
1) Secretion of water, bicarbonate, and Bile from Pancreatic & Bile Ducts
2) Increases rate of Bile Secretion from Liver
3) Inhibits Gastric Secretion and Motility
What is Gastric Inhibitory Polypeptide?
Digestive Hormone that:
1) Inhibits Gastric Secretion & Motility
2) Encourages release of Insulin
