GI absorption Flashcards
what does absorption refer too
small molecules move through epithelila cells into underlying blood or lymphatic vessels
where does absorption tend to occur
-about 90% occurs in the small intestine
-10% in the stomach and large intestine
-any undigested or unabsopred material is passed into large intestine
how does absorption occur in the small intestine
simple diffusion, facillitated diffusion, osmosis and active transport
what kind of substances can diffuse through cell membeane without the aid of a channell
small, lipid soluble substances
e.g. steroid hormones
name the 2 types of active transport mechanisms and describe them
-Primary active transportdirectly uses a source of chemical energy (e.g., ATP) to move molecules across a membrane against their gradient.
-Secondary active transport(cotransport), on the other hand, uses an electrochemical gradient – generated by active transport – as an energy source to move molecules against their gradien
why is the sodium-potassium pump a key in the intestinal absorption
-moves 3 Na ions out of cells and 2K into them.
-also plays a major role in generating voltage across cell membrane
what macronutrients and micronutrients need to be absorped
macronutrients:
-Carbohydrates
-Lipids
-Proteins
micronutrients:
-Nucleic Acids
-Vitamins
-Minerals
-Water
-Drugs
discuss the carbohydrate startch
-long chains of glucose units (polysacharides)
-found in rice,pasta,potatoes ect
discuss the carbohydrate sugar
-shorter chains (mono-or-dissacharides)
-found in fruit and veg or dairy
what may a person experience who lacks the enzyme lactase
lactose intolerance
-diarrhoea
-flatulence
which monosaccharides require energy for absoprtion
-glucose
-galactase
why is fructose unable to be transported against electrochemical gradient
because its absoprbed by facillitated diffusion
discuss proteins and how we absorb them
-dietary sources of protein (meat,fish,eggs,)
-imtake varies across world
-also absorb proteins from digestive juices and dead mucousal cells
-long chains of amino acids (polypeptides)
name the proteins found in the following organs and describe what they do
stomach
-pepsin
produce smaller polypetide chains
pancreas
-trypsin
produce small peptide chains
small intestine microvilli
-specific peptidases
produce tripeptides, dipeptides and amino acids
what absorbs Di and Tri peptides
taken up by PepT1
-allows AAs to be liberated and absorbed into bloodstream
define lipids and list examples of some
sunstances that are more soluble in organic solvents than water
-triglycerides
-phospholipids
-cholesterol
-steroids
-fat soluble vitamins
what are the effects of lipases triglycerides
break them into monoglycerides and fatty acids (short or long chain)
discuss emulsification of lipids
breaks large lipid droplets into smaller droplets
-increase the surface area
-begins in stomach without churning
bile salts
-hydrophillic and hydrophobic regions
Recombined in sER of SI epithelial cells
FFA + monoglyceride → triglyceride
Proteins added
Chylomicrons formed
Triglycerides (90%)
Cholesterol (5%)
Phospholipids (4%)
Protein(1%)
why do chylomicrons enter lymph rather than blood
how do they then enter the bloodstream
-they are too large to enter the blood
-lymphatic capillaries lack basement membrane and are more permeable to large particles
-they travel through lymphatic system to thoracic duct into bloodstream and then by blood to adipose tisseu
list some organic substances that cannot be manufactured in the body
-vitamin C
-thiamine
-vitamin D
-vitamin A
-B12
discuss vitamin absorption in the small intestine
fat-soluble vitamins -(A,D,K,E) carried by micelles and then diffuse into absorptive cells
water soluble vitamins- (C,B) absorbed by diffusion or by passive or active transport
vitamin B12-binds with intrinsic factor, is absorbed by endocytosis
discuss vitamin absoption in the large intestine
-vitamin K and B vitamins from bacterial metabolism are absorbed
why would a bile duct blockage lead to vitamin E deficinecy
-vitamin E is a fat soluble so must be carried via a micelle
-bile duct delivers bile to SI to allow micelle generation
discuss electrolytes
-mostly along the length of small intestine
-usually active transport
ron and calcium absorbed in duodenum
-ionic iron is stored in mucosal cells with ferritin
-Ca2+ absoprtion is regulates by vitamin D and parathyroid hormone (PTH)
