Samenvatting - HNH28305 Metabolic Aspects of Nutrition
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Course
Metabolic Aspects of Nutrition (HNH28305)
Institution
Wageningen University (WUR)
Samenvatting/ aantekeningen van het volledige vak metabolic aspects of nutrition. Uitgebreide samenvatting met uitleg van moeilijke principes. Voornamelijk in het Engels maar ook stukjes in het Nederlands
Galblaas
Gal
Productie in levercellen, opslag in galblaas
Galzouten worden efficiënt gereabsorbeerd (in ileum): enterohepatische cyclus
o Natrium symport
Cholesterol:
Alleen afgifte door gal
Als cholesterol of als galzouten
Primaire mechanismen nutrient opname
Vertering en opname eiwitten
Maag
Maagzuur:
o Denaturatie (uitscheiding door pariëtale cellen)
Protease
o Pepsine (uitscheiding door chief cellen als pepsinogeen)
Dunne darm
Proteasen
o Pancreatische proteasen
o Brush-border proteasen op enterocyten
Vooral opname als di- en tripeptiden (80%) (20% aminozuren (afbraak naar aminozuren in darmcellen))
Absorptie aminozuren
Verschillende transporteiwitten
Transporters hebben
o Stereospecifiek (L-aminozuren)
o Substraat specifiek
o Overlap in specificiteit (multiple transporters per aminozuur
Mechanisme
o Gefaciliteerde diffusie
o Secundair actief transport (NatriumKalium pomp, ATP, co-transport)
Efficientie: 95-99%
o 30-35% als aminozuur
o 70% di- en tripeptides
, COLLEGE 2
VERTERING EN OPNAME VAN NUTRIËNTEN – DEEL 2
Protein digestion & absorption
Stomach:
Gastric acid: denaturation (parietal cells)
Protease: pepsin (chief cells: pepsinogen)
Small intestine
Protease: pancreatic protease
Brush-border protease (on enterocytes)
Peptidase on brush border: protein di- & tripeptides
PEPT1 = peptide transport protein
Low affinity: most di- & tripeptides can be transported
Broad substrate specificity
Secondary active transport (H+ influx, H+ exchange with Na+)
o Also Na/K pump to produce ATP in cell (Na+/K+-ATPase)
Facilitated transport (cotransport)
Efficient absorption: 95-99%, 30-35% AA, 70% di- & tripeptides
Summary:
1. Brush-border membrane peptidase: protein AA / di/tri-peptides
2. Brush-border membrane amino acid transporters
3. Brush-border membrane di- and tripeptide transporters
4. Intracellular peptidases: peptides AA
5. Basolateral-membrane amino acid carriers: AA (lumen blood)
6. Basolateral-membrane di- and tripeptides carriers
AA supplements
AA slower absorbed than di- & tripeptides
Toxicity: tryptophane
Branched carbohydrates are digested faster: digestion enzymes have more endings where digestion can be started
Normally lactase disappears over time, Western countries highly mutated, still having lactase as adults
Lactose intolerance
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