Lecture7-1notes

Lecture7-1notes - 10/8/10 Absorp&on: small...

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Unformatted text preview: 10/8/10 Absorp&on: small intes&ne Diges&on 2 10/11 Absorp&on: small intes&ne •  Difference between crypt and &p –  Tip: absorp&on •  Carbohydrates, amino acids, small pep&des •  Pep&des: Fig. 14 ­23 –  Taken up by endocytosis across apical membrane –  Processed into amino acids intracellularly by lysosome pathway –  Exit on amino acid transport systems on basolateral Sherwood, Klandorf, Yancey Fig. 14-23 membrane Absorp&on: small intes&ne •  Specific transport systems •  Specific transport systems •  Carbohydrates, etc. •  Pep&des •  Fats –  Present in lumen as micelles, emulsified by bile salts –  Cross apical membrane by simple diffusion –  Chemically modified in e. r. –  Processed by Golgi into chylomicrons –  Exit cells by exocytosis •  Carbohydrates, amino acids, small pep&des •  Pep&des •  Fats: Fig. 14 ­24 –  Cross apical membrane by simple diffusion –  Chemically modified in e. r. –  Processed by Golgi into chylomicrons –  Exit cells by exocytosis –  Too large to cross endothelium of blood vessels »  Enter circulatory system via lymph Sherwood, Klandorf, Yancey Fig. 14-24 1 10/8/10 Absorp&on: small intes&ne Absorp&on: small intes&ne &p •  Difference between crypt and &p –  Tip: absorp&on •  Carbohydrates, amino acids, small pep&des •  Pep&des •  Fats •  Ions Crypt vs &p Tip: absorbs nutrients Crypt: secre&on –  Many specific transport systems Sherwood, Klandorf, Yancey Fig. 14 ­19c Absorp&on: small intes&ne •  Difference between crypt and &p –  Tip: absorp&on –  Crypt: secre&on •  Secretes water into lumen (mucosa) by secre&ng NaCl (review leaky secretory epithelia) •  Func&ons –  Lubrica&on –  Salt/water balance •  Hormonal control: cholera disrupts Diges&on •  •  •  •  Head gut: mouth Midgut: stomach Small intes&ne Hindgut: large intes&ne – Water absorp&on •  Driven by Na+/Cl ­ absorp&on •  Major organ for water balance •  Major organ for water balance •  Recovers water moving through gut 2 10/8/10 Large intes&ne •  Water absorp&on – Recovers water moving through gut – Water comes from •  Ea&ng, drinking •  Secre&on Diges&on •  •  •  •  –  Salivary, gastric, pancreas, gall bladder –  8 liters per day in humans! Nutrient processing •  •  First stop for both blood and lymph: liver Liver is major homeosta&c organ Head gut: mouth Midgut: stomach Small intes&ne Hindgut: large intes&ne – Water absorp&on – Mucous secre&on – Control elimina&on Nutrient processing •  Liver func&ons –  Carbohydrates •  Convert various sugars to glucose: major transported sugar •  Mediate glucose glycogen, as a func&on of availability and metabolic demand 3 10/8/10 Nutrient processing •  Liver func&ons Nutrient processing •  –  Carbohydrates –  Fats •  Major source of energy for most cells Cholesterol –  Some converted to bile salt –  Some packaged for transport •  –  Highly reduced: more energy per C –  Insoluble: does not interfere with osmo&c balance •  Not soluble, so must package for transport Nutrient processing •  Cholesterol –  Some converted to bile salt –  Some packaged for transport •  Low density lipoprotein: LDL –  Rela&vely high fat, therefore low density –  Job: cholesterol/fat donor –  “Bad” cholesterol: donates cholesterol to plaques Low density lipoprotein: LDL –  Rela&vely high fat, therefore low density »  25% protein »  50% cholesterol »  25% other fats Nutrient processing •  Cholesterol –  Some converted to bile salt –  Some packaged for transport •  •  Low density lipoprotein: LDL High density lipoprotein: HDL –  Lower fat content »  50% protein »  20% cholesterol »  30% other fats 4 10/8/10 Nutrient processing •  Cholesterol Nutrient processing •  –  Some converted to bile salt –  Some packaged for transport •  •  Low density lipoprotein: LDL High density lipoprotein: HDL –  Lower fat content –  Job: pick up fats and return to liver –  “Good” cholesterol: prevents plaque forma&on •  •  •  •  Nitrogen catabolism •  Excess amino acids catabolized for energy •  Converted to α-keto acid and ammonia H O HOOC ­C ­R HOOC ­C ­R NH2 NH3 Liver func&ons –  Carbohydrates –  Fats –  Proteins Carried in blood as amino acids Taken up as needed by cells and converted to proteins Myosin acts as storage reservoir Excess amino acids catabolized for energy Nitrogen catabolism •  •  Excess amino acids catabolized for energy Converted to α-keto acid –  Accumula&on of α-keto acids one reason for decreased appe&te on high ­protein diet –  Altera&on of insulin due to low carbohydrates a major reason for decreased appe&te 5 10/8/10 Nitrogen catabolism Nitrogen catabolism Excess amino acids catabolized for energy Converted to α-keto acid α-keto acids fed into TCA cycle in mitochondria •  Fate of NH3? Cf. pp. 522 ­525 •  •  •  Fate of NH3 Secrete directly : ammonotelic: FW animals –  •  What is characteris&c of FW animals that enables them to excrete toxic ammonia? Sherwood Klandorf Yancey Fig. 12 ­1 Nitrogen catabolism Nitrogen catabolism •  •  Fate of NH3 Fate of NH3 –  Secrete directly : ammonotelic: FW animals –  Convert to urea –  Secrete directly : ammonotelic: FW animals •  •  Copious, dilute urine – Excre&on = urine flow rate x Curine – With high urine flow rate, can have high excre&on even with low Curine O What is urea? C H2N NH2 Sherwood Klandorf Yancey Fig. 12 ­1 6 10/8/10 Nitrogen catabolism Nitrogen catabolism •  –  –  –  Fate of NH3 •  Fate of NH3 –  Secrete directly : ammonotelic –  Convert to urea: ureotelic –  Convert to uric acid: uricotelic Secrete directly : ammonotelic Convert to urea: ureotelic What is urea? Highly soluble, less toxic than NH3 •  •  What is uric acid? Purine: not very soluble Who uses urea? –  Mammals, amphibians, fish, echinoderms, snails Sherwood Klandorf Yancey Fig. 12 ­1 Nitrogen catabolism Nitrogen catabolism •  Fate of NH3 •  –  Secrete directly : ammonotelic –  Convert to urea: ureotelic –  Convert to uric acid: uricotelic Fate of NH3 –  Secrete directly : ammonotelic –  Convert to urea: ureotelic –  Convert to uric acid: uricotelic •  Purine: not very soluble •  Who are uricotelic? Birds, rep&les, land crabs, insects •  Organisms may alter secre&on between life phases, e.g., rep&les –  Embryo in egg forms uric acid –  Adults excrete urea Tend to deposit nitrogen waste along with feces as insoluble paste Sherwood Klandorf Yancey Fig. 12 ­1 7 ...
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This note was uploaded on 09/16/2011 for the course BIO 203 taught by Professor Loretz during the Fall '09 term at SUNY Buffalo.

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