Section 10 Nutrients & Their Functions 1. Acquiring nutrients Digestion & absorption of carbohydrates & proteins 1/3/06.

Slides:



Advertisements
Similar presentations
Moving along the GI tract
Advertisements

Single stomach Eat feed low in fiber Humans are also non-ruminants.
Major food groups Carbohydrates = sugars = saccharides Lipids = fats Proteins nucleic acids  Carbohydrates, proteins and nucleic acids (but not fats)
Digestion and Absorption Of Proteins Prof. Dr. Arzu SEVEN.
Proteins.
Portland Community College
Catalytic Mechanism of Chymotrypsin slide 1 Chymotrypsin –Protease: catalyze hydrolysis of proteins in small intestine –Specificity: Peptide bond on carboxyl.
Pancreatic secretions The pancreas acts as an exocrine gland by producing pancreatic juice which empties into the small intestine via a duct. The pancreas.
Hormonal control in the Digestive system: Gastric hormones
Digestive System Chapter 18.
Human Biology: Digestive System
Lecture 5 Dr. Zahoor Ali Shaikh
THE HUMAN DIGESTIVE SYSTEM THE CHEMICAL DIGESTION.
Metabolic fuels and Dietary components Lecture - 5 By Dr. Abdulrahman Al-Ajlan 1.
Digestive Process and Enzymes. Review What is the difference between physical digestion and chemical digestion? What is an enzyme? Why are enzymes specific.
Physiology of Gastrointestinal System (L6) Physiology of The Pancreas
Digestive and absorptive functions of the gastrointestinal system 1.
Lab Activity 30 Digestive Enzymes Portland Community College BI 233.
Ex 39A Digestive Enzymes. Energy Transfer in Chemical Reactions Forming new bonds can either release or absorb energy Chemical reactions usually involve.
1Dr.S. Nayak Digestion Digestion The human diet contains carbohydrates, fat and proteins, which are high molecular weight complex compounds. All have to.
Digestion Overview. salivary α-amylase, mucins - parotid, submandibular, sublingual glands lingual lipase - lingual serous bicarbonate ion, mucus - mucosal.
Nutrient Digestion Site of Absorption Carbohydrates
GASTROINTESTINAL PHYSIOLOGY Chapter-II (DIGESTION and ABSORPTION)
Digestion of Dietary Carbohydrates. Main Carbohydrates of Diet 1- Monosaccharides: mainly glucose & fructose ABORBED with NO DIGESTION 2- Disaccharides:
Digestion and Absorption Johnson Chap Jack L. Leonard 2004.
Digestive System Topic 6 – Human Anatomy and Physiology Van Roekel – IB Biology 2.
PROTEIN METABOLISM: NITROGEN CYCLE; DIGESTION OF PROTEINS Red meat is an important dietary source of protein nitrogen.
© CU/SONMS/nutrition/CSSAN Digestion &Absorption of every day foods.
Digestive System Jeopardy Directions In Jeopardy, remember the answer is in the form of a question. Select a question by clicking on it. After reading.
Anatomy and Physiology Part 4: Pancreas and Pancreatic Control
Molecular breakdown/absorption of Polysaccharides Lipids Proteins
Pancreas.
Digestion Food: The easiest thing you will pass in school.
Digestion & Absorption of Proteins Lecture by: Dr. Samia Naz (APWMO) Biochemistry Department, KEMU.
Dr Pradeep Kumar, Professor department of physiology, KGMU, Lucknow.
Protein digestion Peptidases are enzymes responsible for protein digestion Types of peptidases: Endopeptidases: e.g. pepsin, trypsin, chymotrypsin and.
PANCREATIC SECRETION DR. AMEL EASSAWI DR. SHAIKH MUJEEB AHMED 1.
Human digestion. Human digestive system (General plan) Accessory digestive organs.
- No absorption in esophagus, little in the stomach and vast majority of absorption occurs in small intestine. - The small intestine has specialized structures.
Lecture 51 : Digestion and absorption of protein Digestion and absorption of protein ط Peptidases : Gastric and Intestinal ط Pancreatic peptidases ط Amino.
Digestion of proteins Dr. Samah Kotb Lecturer of Biochemistry 2015 Cellular Biochemistry and metabolism 1 CLS 331.
Dr. Mohammed Vaseem Assistant Professor Biochemistry Explain the process of digestion & absorption of proteins and carbohydrates in the GIT.
Biochemical Aspects of Digestion of Proteins and Carbohydrates (GIT/Hematology Block) Dr. Ahmed Mujamammi Dr. Reem Sallam.
Digestion of proteins.. Protein digestion Digestion in Stomach Stimulated by food acetylcholine, histamine and gastrin are released onto the cells of.
Gastrointestinal Physiology – Part 2 11/04. Digestive secretions: saliva Functions of saliva in non-ruminants: –Lubricates food to facilitate swallowing.
BIOC Dr. Tischler Lecture 21 – February 14, 2006 METABOLISM: PROTEIN DIGESTION & ABSORPTION.
Digestion and absorption of Proteins
Biochemical Aspects of Digestion of Proteins & Carbohydrates
Digestion of Proteins and Amino Acids
Summary of Digestion of Carbohydrates
Physiology.
Digestion and Absorption
Digestion and Absorption of Proteins
Digestion of carbohydrates, proteins & fats - Dietary substrates, enzymes, end-products of digestion.
Mechanical vs. Chemical Digestion
6.1 - Digestion.
22.3 Digestion of Carbohydrates
The digestive system.
Deanna Page, Mike Lin, Mali Bowers, Gayle Seales
6.1 - Digestion.
Digestion & Absorption
L. digestion and absorption
Human digestion.
Pancreatic Secretions
Pigs are non-ruminants
Physiology.
4. Proteins Lecture 3.
Digestion Topic 6.1 (modified for 2016 exam).
FHB-(Digestion-Absorption-Metabolism) Sandwich Conference 2019
Digestion and Absorption Of Proteins and its Disorders
Presentation transcript:

Section 10 Nutrients & Their Functions 1. Acquiring nutrients Digestion & absorption of carbohydrates & proteins 1/3/06

Section 10 Acquiring Nutrients Overviewnutrients digestion, absorption glucose, amino acids, fats distribution precursors, available fuels metabolism macromolecules, energy, end products 1

Digestion: general features u general function: convert nutrients into absorbable form u larger molecules (macro)  smaller molecules u chemical reaction: hydrolysis H 2 O + RX YR'  RXOH + HYR' where X = C, P Y = O, N H 2 O + RX – YR'  RXOH + HYR' where X = C, P Y = O, N u reaction catalyzed by hydrolases major nutrientshydrolase typebond cleaved poly, oligosaccharidesglycosidaseglycosidic proteins, peptidesprotease, peptidasepeptide fats (triglycerides)esteraseester minor nutrients phospholipids, nucleic acidsphospholipase, nucleasephosphoester esters ( e.g., cholesterol, retinol )esterasesester H2OH2O 2

Activation of hydrolases u noncovalent activator binds reversibly to enzyme examples: enzymeactivator  -amylase Cl – lipasecolipase u covalent activator catalyzes hydrolysis of one or more peptide bonds of precursor activator precursor  active enzyme (proenzyme or zymogen) HCl examples:pepsinogen  pepsin HCl examples:pepsinogen  pepsin trypsin trypsin proelastase  elastase 3

Carbohydrates: digestion (poly   oligo) u only monosaccharides are absorbable u Stage I: polysaccharides  oligosaccharides enzyme:  -amylase (specificity: internal  1,4 glucosidic bonds) enzyme:  -amylase (specificity: internal  1,4 glucosidic bonds) sources: salivary glands (minor) & pancreas (major) l substrates: amylose (only  1,4 links ) products: maltose, maltotriose 4 (glc 3 )

Carbohydrates: digestion (oligo   mono) u Stage II: oligosaccharides  monosaccharides source of enzymes: mucosal cell surface (brush border) source of enzymes: mucosal cell surface (brush border)  -limit dextrins  glc 3 + glcisomaltase + maltose(  -dextrinase) α 1,6 glucosidic bonds maltose  2 glcmaltase maltose  2 glcmaltase glc 3  3 glc " glc 3  3 glc " sucrose  glc + fructosesucrase sucrose  glc + fructosesucrase lactose  glc + gallactase (inducible) lactose  glc + gallactase (inducible)  -limit dextrins: (glc) with one  1,6 linkage glc: glucose gal: galactose glc: glucose gal: galactose 5

Carbohydrates: absorption from lumen u frc & mannose facilitated diffusion (carrier-mediated) u glc & gal l transported against concentration gradient l cotransport (Na + gradient-driven symport) l aka secondary active transport u pentoses, others absorbed via simple diffusion Na + glc symport protein 6

glc-Na + symport animation u for “snapshots” of this animation, see the next slide u stop animation by clicking browser’s Stop button u resume animation by going to another slide, then return- ing to this one glc-Na + symport protein 7

glc-Na + symport mechanism 1. outer gate open, sites unoccupied 2. sites occupied, outer gate closing 3. inner gate opening 4. Na +, glc dissociating 5. inner gate closed, outer gate opening glc-Na + symport protein 7

Glucose movement: lumen  blood lumen of small intestine glucose (lower conc.) glucose (lower conc.) glucose (higher conc.) glucose (higher conc.) interstitial fluid blood Na + glc transporter (symport) GLUT2 glucose carrier (facil. diffusion) mucosal cell 8 Na +,K + ATPase Na + K+K+K+K+ K+K+K+K+ u transport into mucosal cell (enterocyte) l across luminal (apical) membrane l against concn. gradient l Na + glc symport u transport out of mucosal cell l across contraluminal (basolateral) membrane l down concn. gradient l glc transporter (GLUT2)

Proteins: digestion to peptides & amino acids u only amino acids & some small peptides absorbable u stomach: food polypeptides stimulate G-cells in pyloric region to secrete the hormone gastrin u gastrin stimulates parietal cells to secrete HCl u effects of HCl l denatures (unfolds) proteins l solubilizes iron, other metals (ions) l inactivates pathogenic organisms (antiseptic) l stimulates secretion of secretin & cholecystokinin (CCK) l activates pepsinogen l in bulimia, erodes enamel 9

Proteins: gastric digestion u peptidases (proteases, proteolytic enzymes) l exopeptidases: peptide bonds next to N- or C-terminus l endopeptidases: bonds not next to N- or C-terminus u pepsin l endopeptidase l secreted as pepsinogen by chief cells l activation: catalyzed by HCl, pepsin (self-activation) l specificity: bonds next to aromatic side chains (phe, tyr, trp) l an aspartate protease (2 asp at active site; slide 14) u main result of passage through stomach: polypeptides unfolded & converted to large peptides + OOOO + OOOO H 3 NCC–NCC–NCC–NCC–NCCOO – exoendoendoexo (stimulus: gastrin) 10

Gastric secretions & digestion u HCl secretion by parietal cells u pepsinogen secretion by chief cells u pepsinogen activation by l HCl l pepsin autocatalysis: product activation of precursor Sherwood, Fig HCl, pepsin pepsin pepsinogen 11 Shrwd5_16-11.jpg

Proteins: intestinal secretions & digestion u HCl, peptides in chyme stimulate duodenum to secrete l CCK: stimulates pancreas to secrete enzyme - rich juice l secretin: stimulates pancreas to secrete HCO 3 – - rich juice l gastric inhibitory peptide: inhibits antral contractions u HCO 3 – raises pH of chyme to 7- 8 u pancreatic proteases: trypsin ( an endopeptidase ) l secreted as trypsinogen l trypsinogen activated by enteropeptidase* (mucosal cells) & by trypsin (self-activation) l important as activator of many other digestive enzymes l specificity: bonds next to cationic side chains (lys, arg) l a serine protease (contains a catalytic triad; slide 14) * aka enterokinase 12

Intestinal digestion by peptidases u pancreas also secretes trypsin inhibitor u other pancreatic peptidases peptidasetypeactivatorside chain specificity chymotrypsinendotrypsinnonpolar, aromatic elastase " "small, aliphatic carboxypep- tidase Aexo "nonpolar, aromatic " B " "cationic " B " "cationic u mucosal cell luminal surface peptidases l aminopeptidase (peptide bond next to N-terminus) l dipeptidase (dipeptides) 13

Protease classes or families u all proteases belong to 1 of 4 classes u classification based on main catalytic site feature protease class examples serine (section 4) trypsin, chymotrypsin, elastase, thrombin, plasmin thrombin, plasmin zinc "carboxypeptidases, thermolysin thiol (cysteine)papain, cathepsins (lysosomes) aspartatepepsin, renin, HIV-1 protease u within a class, substrate specificity due to structure of part of the active site: the specificity site 14

Serine proteases: specificity pocket u binding pocket structured to favor side chains on substrate that are: l nonpolar/aromatic chymotrypsin l cationic trypsin l small elastase gly 216 gly 226 gly 216 thr 216 gly 226 val 226 asp 189 ser 189 chymotrypsin trypsin elastase + –+ – N N N 15

Absorption of peptides & amino acids from GI lumen u amino acids l Na + gradient-driven symports (cotransport) mechanism same as glucose–Na + symport l at least 6 kinds of symport proteins l specificities by amino acid types examples: small, polar side chains (ala, ser, thr) cationic side chains (lys, arg) anionic side chains (asp, glu) 16

Absorption of peptides & amino acids u some small peptides are absorbed l mostly di- & tripeptides l H + gradient-driven symport l absorbed peptides hydrolyzed to amino acids by cytosolic peptidases u amino acids reach portal blood via facilitated diffusion across contraluminal membrane of mucosal cells l mechanism same as monosaccharide systems l specific transmembrane carrier proteins 17

lumen of small intestine amino acids interstitial fluid blood Na + aa symport amino acid carriers (facil. diffusion) mucosal cell 18 Na +,K + ATPase Na + H+H+H+H+ K+K+K+K+ K+K+K+K+ u analogous to glc movement (slide 8) u absorption via symports l aa: Na + gradient-driven l peptides: H + gradient-driven  in cytosol: peptides  amino acids u aa’s cross contraluminal membrane via facilitated diffusion carriers Na + small peptides H+H+H+H+ peptidases Amino acids, peptides movement: lumen  blood H + peptide symport

Study questions u Describe step-by-step the processes of digestion, absorption, and distribution of proteins. Include the roles of enzymes, activators, hormones, and membrane transport. u Do the same for carbohydrates.

Next time: Digestion & absorption of lipids