Introduction to MetabolismConcept of metabolism, catabolism     طAnabolic and catabolic pathways     طImportant consideration for metabolism of carbohydrates, Protein and Lipid     طOverview of metabolic pathways, energetic and regulation     ط                           D4 268-269  , 362-363  ,446-447

Introduction1. Metabolism:

intracellular biochemical reaction involve synthesis, conversion, transport & breakdown of various compounds.

2. Anabolism (-genesis): synthesis reactions in metabolism.3. Catabolism (-lysis): breakdown of metabolites or oxidation:

stored in the form of ATPATP ENERGY ADP + Pi ENERGY AMP + Pi

a) Energy produced from high energy compound: e.g. ATP, GTP, UTP     -ATP to ADP = 13000 kcal

ADP to AMP = 1200 kcalAMP to A = 3000 kcal

b) Substrate level phosphorylation: S-P + ADP S + ATP c) Oxidation phosphorylation: 

-NADH + H     3 ATP-FADH2            2 ATP

Carbohydrate Metabolism1.        fig7.1: GLYCOGEN (glucose storage) GLUCOSE PYRUVATE  …..

2.        Defect in Glc metab causes OBESITY & DIABETES:Atherosclerosis, hypertension, kidney disease, blindness

Lipid Metabolism1. FA lipid molecules (nonpolar/hydrophobic)2. fig9.1: TG (FA storage) FA FA / albumine,

TG/LP, KB FA ACoA …..3. Lipid functions: a) Oxidation of FA ENERGY b) Hydrophobic Structure, FA bound to:

-carbohydrates (Glycolipids)  -organic phosphate (phospholipids) c) Surface active Properties:

-maintenance of lung alveolar integrity-solubolization of nonpolar substances in body fluid-steroid hormones & prostaglandins in metabolic control

4. Deficiencies cause:      obesity, diabetes, ketoacidosis & abnormal lipid transport   Refsum's Disease & familiar hypercholesterolemia

Amino Acids Metabolism1. fig11.1: H2 BACT/PLANT/LIGHT NH3 (ammonia) INCORPORATED AA/Prt (Diet)excretion of NH3 involve sythesis & degradation: Glu, Gln, asp, asn, ala, arg2. T11.1:          

-Essential: from diet-Nonessential: de novo biosynthesis

3. T7.2: -Glucogenic: carbon source for Glc synthesis, to Pyr, 3PG, a-KG, OA, Fum, SCoA-Ketogenic: cannot function as carbon source, to ACoA or acetoacetate

4. fig11.2: carbon enters in 7 points

a) nonessential b) essential

Digestion and absorption of carbohydratesDigestion and absorption of carbohydrates     طTransport of Monosaccharides     ط glucose transporters     طInsulin effect on different transporter     طLactose intolerance     ط                                         D4 1073-7

Carbohydrates Digestion5. Polysaccharides (Branched 100,000 glc mol):

α-1, 4-glucosidic bond (amylose)α-1, 6-glucosidic bond (amylopectin)

a) Starch (plant); α-1, 4-bond:α-1, 6-bond (ratio 20:1) b) Glycogen (animal); more branches6. Poly- AMYLASE (salivary & pancreatic) Di- (maltose) MALTASE Mono …..fig7. poly- or oligo- (e.g. beans) or di- (e.g. young mushrooms) BACT. (lower ileum)

….. figthis will cause anaerobic hydrolysis è gases è diarrhea

Monosaccharide Absorption1. Intest Luman; Mono- transported by SGLT1:

Na+-dependent active transport specific for Glc, Gal    by Na+-independent facilitative diffusion:

-GLUT5 for Fru     -GLUT for all mono2. Mono transporters or glc trans (GLUT1, 3, 4 ) …… Table 3. Insulin Effect on transporters: a) INS-insensitive glc transport system, GLUT2 (liver):

Rapid glc uptake & release b) INS-sensitive glc transport system, GLUT5 (muscle/AT):

insulin-stimulated glc uptake

Table: Monosaccharides Transporters

 LocationFunction

Facilitated-diffusion Transporters

GLUT 1Brain, Kidney, RBCsGlucose uptake

GLUT 2Liver, S. intestine, KidneyRapid glucose uptake & release

GLUT 3Brain, KidneyGlucose uptake

GLUT 4Muscle, Adipose tissueInsulin-stimulated glucose uptake

GLUT 5S. intestineFructose absorption

Active Na+-dependent Transporter

SGLT 1S. intestine, KidneyGlucose & galactose absorption & transport

Cytochalasin N is an inhibitor of GLUT 2Pholorizin is an inhibitor of SGLT 1

Intestinal Disaccharide Deficiencies: cc26.4 a) In 1 enzyme or more b) Reasons: genetic, age, injury c) Most common is LACTOSE deficiency (milk, lactose intolerance) d) Lower ileum Bact. fermentation causes gas & osmosis lead to diarrhoea e) Yogurt contain partially hydrolyzed lactose f)  The enzyme lactase is commercially available