Absorption

• Maltase (breaks down maltose), sucrase (splits sucrose into glucose and fructose) as they can cleave internal and terminal 1-4 • isomaltose (can cleave alpha limit dextrin’s as it cleaves 1-6) Lactase which breaks down lactose

Intraluminal digestion (salivary enzymes and pancreatic enzymes in the GI tract) and membrane digestion (microvilli on the brush border convert oligosaccharides to monosaccharides)

jejunum

Intraluminal digestion occurs via proteases excreted by the gastric and pancreatic cells (secreted as proenzymes activated by low PH and enterokinases on the brush border respectively)

endopeptidases (cleave after specific amino acids within polypeptide chain) exopeptidase (cleave specific peptide bond adjacent to the C terminus)

can absorb intact antibodies from mothers breast milk via endocytosis otherwise peptides have to be oligopeptides or amino acids to be absorbed

secreted from chief cells in the stomach, or acinar cells in the pancreas where they are activated in the small intestine, membrane of enterocytes (membrane digestion)

PepT1- H+ cotransporter (oligopeptides and H+ into cells), Na+ cotransporter of AA, Na+ independent AA transporters on the basal side

cysteine stone formation in renal system due to mutated channels leading to deficient cysteine uptake in the intestine

• Retinol (animal form), Beta Carotene (Plants) • Needed to form rhodopsin a key component of the eye for detecting light Deficiencies lead to light blindness

• Also know as alpha-tocopherol • Major source is oily food • Antioxidant, turn of oxidants produced by immune cells to kill pathogens • Deficiencies damage caused in many areas of the body / poor immune system function due to the build-up of oxidants

• Can get it from sunlight, if lack sufficient sunlight need to consume it in our diet • Vitamin D deficiency = bone softening also known as osteomalacia also have demineralisation

• Green leafy vegetables are a major source • Produced by macrobacteria in the gut • Deficiencies are uncommon but supplements are given to babies • Needed for prothrombin formation so deficiencies = excessive bleeding

dissolved within micelles in the small intestine to aid adsorption

energy storage molecule that provides a large source of energy and insulation essential for membrane formation as essential fatty acids cannot be endogenously produced

There are lingual, gastric (from chief cells) and pancreas lipases

emulsifies fat globules (micelle) this gives a large surface area for lipase to work provides optimum PH for lipases

come from the pancreas and anchors the lipase to the micelle so catalytic activity can occur without the lipase being washed off by bile salts

at low PH’s they work more optimally when they reach the stomach they work minimally in the mouth at neutral PH

diglycerides = single fatty acids and monoacylglycerol

passive diffusion through enterocytes

as triglycerides are broken down longer fatty acids remain with the lipid droplet shorter ones can diffuse into the solution and across the gastric mucosa a new core lipid will replace what is lost to be broken down and the micelle will get smaller and smaller

protonated at the low PH of the enterocyte brush border then absorbed by diffusion, carrier mediated transport or integrated into the cell membrane

Na+/H+ antiporter in the enterocyte