BIO Exam 2: Nutrient Uptake and Transport Flashcards
Nutrient Uptake and Transport
Lots of digestion in the small intestine lumen
* Amylase
* Lipase
* Trypsin, Chymotrypsin
Need to transport out of the lumen
Carbohydrate Uptake
mostly digested to mono-and disaccharides
active transport
Energy Transfer:
ATP to Na+ gradient.
Na+ gradient to Glucose.
Amino Acid Uptake
Amino acid uptake is very similar
* Na+/Amino acid symport in apical membrane
* H+/Di- and tripeptide symport in the apical membrane
* Facilitated amino acid transporters in basal membrane
Bile salts are reabsorbed similarly
Nutrient Uptake
Crossed the epithelial cell to ECF
Solutes diffuse into capillary pores
Leave in venules
Does not go directly to heart
Hepatic portal vein delivers blood to liver
New capillary bed in liver before returning to the heart
In this action, Bile salts absorbed some molecules, detoxified nutrients, and processed nutrients.
Nutrient Uptake (2)
Most amino acids and monosaccharides remain in blood plasma
Can be absorbed by any cell that needs them, typically by facilitated transport
Lipid Uptake
Emulsified by bile salts into micelles Triglycerides → Free fatty acids in intestine lumen by lipase
Fatty acids can diffuse, leaving micelles and crossing the phospholipid bilayer
Steroids also diffuse into cells
Lipid Uptake (2)
Fatty acids diffuse to ER
Synthesized into Triglycerides
Combined with lipoproteins(made on Rough ER) and also steroids and other lipids
Lipid Uptake (3)
Forms a large Chylomicron within ER
Triglycerides in middle
Covered by phospholipids and steroids
Organized by lipoproteins
Lipid Transport
Chylomicron leaves the cell by exocytosis at the basal membrane
Chylomicron is far to large to enter capillary
Enters a lymph vessel, the lacteal then flows through lymph system
ultimately enters plasma
Lipid Transport (2)
Triglyceride → Fatty acids in intestine lumen
Diffuse across plasma membrane
Fatty acids → Triglyceride in ER
Chylomicron assembly
Exocytosis
To lymph
Lipid Transport (3)
Lipoprotein Lipase is a membrane-bound protein in some capillary endothelial cells
Fatty acids diffuse into tissue. May be metabolized (muscle)or stored as triglycerides (adipose)
Lipid Transport: Chylomicron
reduced in size as triglycerides are removed.
lipoproteins remain
Chylomicron remnant is absorbed by liver
Vitamin Uptake and Transport
Macronutrients:
Often used as energy sources. It can be used to make new macromolecules.
Essential amino acids
Essential fatty acids
Vitamins
Minerals
Essential Amino Acids
Eight amino acids cannot be synthesized (by humans). Must be supplied in the diet
Examples:
1) linolenic acid: C18 with three unsaturations (omega-3)
2) inoleic acid: C18 with two unsaturations (omega-6)
Nutrient Uptake and Transport
Vitamins:
small organic molecules needed in small amounts for health
Some water-soluble; some fat-soluble
Usually act as co-factors for enzymes .Sometimes chemical messengers
