La spécificité du tadalafil est liée à sa longue demi-vie, permettant une action qui excède largement celle des autres inhibiteurs de PDE5. L’absorption digestive est complète, avec un pic plasmatique atteint en 2 heures environ. Le métabolisme est réalisé via CYP3A4, produisant des métabolites inactifs éliminés principalement dans les fèces. La sélectivité enzymatique est élevée, réduisant les effets indésirables extra-caverneux. Les réactions indésirables fréquentes incluent céphalées, bouffées vasomotrices et troubles digestifs légers. L’activité pharmacologique est stable, indépendamment de l’ingestion d’aliments. Dans les comparaisons de longue durée, acheter cialis pas cher est mentionné en relation avec les études portant sur la persistance d’efficacité et la constance de la cinétique plasmatique.

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A. Biological Chemistry(though water is the universal medium for life on earth, living organisms are made of chemicals based mostly on the element a. contain Carbon. total of 6e-, 2 in 1st shel , 4 in 2nd that holds 8 i. Carbon has 4 valence electrons that can join with an electron from another atom to form a strong covalent bond-usual y with C, H, O, or N ex/ CH4 (methane) ii. Carbon can bond with other carbon atoms to form large, complex molecules; can be straight, branched, or rings b. C chains form skeletons of most organic molecules c. each repeating unit is called a monomer d. long chain called a polymer; polymers are macromolecules-large, organic molecules i. macromolecules are formed by combining monomers by removing water; called dehydration synthesis or condensation reactions ii. macromolecules are broken down, separated, or digested by e. hydrocarbons-only contain C & H molecules ii. non-polar linkages; can release a lot of energy f. isomers-compounds with same molecular formula, but different structural arrangements (thus different properties) fig 4.7 p62 i. structural-different covalent arrangement of atoms, often ii. geometric-same sequence of covalently bonded atoms, but different spatial arrangements (cis vs. trans) iii. enantiomers-right & left handed versions of each other 3. Carbohydrates (starches & sugars) smal or large, can be monosaccharides, a. main energy source, fuel, & nutrients for cell ex/ glucose, fructose, galactose, deoxyribose, ribose c. simple unit (monomer)-monosaccharide (simple sugars) CH20 Exists in 2 interconvertable forms—alpha glucose (α), and beta glucose (β) (differ in placement of hydroxyl group 3. ID test: Benedict’s: monosaccharides turn green, yellow, d. double sugar-disaccharide (two monosaccharides bonded together by glycosidic linkage) 1. C6H12O6 + C6H12O6 --> C12H22O11 + H2O Water lost when bonded together: dehydration (Water added to break apart: hydrolysis) 2. C12H22O11 --sucrose; most common (table sugar) e. most complex-polysaccharides—many sugar units (macromolecules) 1. long polymers few hundred to few thousand monosaccharides joined 2. ID test: Iodine: polysaccharides turn blue a. plant starch found in breads/grains,potato (stores extra sugar as granules in plastids) 2 forms, amylose & amylopectin b. animal starch (called glycogen) stored in liver & muscle c. cellulose (gives plants their strength/rigidity; primary structure of cell wall; in wood, paper, cotton, d. chitin—cell wall of fungi & exoskeleton of arthropods *humans don’t have enzymes to digest cel ulose & chitin—our enzymes can only digest alpha glycosidic linkages & these have beta* 4. Lipids (fats)-usually small non-hydrocarbon part joined to 3 HC tails a. function-long term energy storage (contains twice as much energy as an equivalent weight of polysaccharide), parts of biological membranes, waterproof coverings, insulation b. composition: C, H, O, & often P (phospholipids) c. saturated-only single bonds (most often solids-animal) unsaturated-some double bonds; most often: oils/plants d. example: triglycerides: 1 glycerol + 3 fatty acids e. lipids don’t consist of polymers; grouped together because they have f. ID tests: translucent spot on brown paper, soluble in lighter fluid, g. phospholipids—phosphate group forms hydrophilic head h. steroids—lipids with a carbon skeleton of 4 fused rings 5. Proteins—examples: insulin, hemoglobin, antibodies, enzymes a. functions: (fig 5.1 p78) support, storage of amino acids, transport cell communication (hormones), movement, defense, growth & repair c. ID test: nitric acid turns proteins yellow (xanthoproteic test) d. monomer- amino acids; have amino group on one end (-NH2) with
basic properties, and carboxyl group on other end (-COOH) with acidic properties. At center is the α carbon, covalently bonded to a hydrogen atom. Other part is called R group (side chain) i. approx 20 found in nature (differ in their R-groups) ii. bonds between amino acids: peptide bonds—fig 5.18 p80 e. polymer-long chain (thousands of amino acids; called polypeptides) f. some function as enzymes-definition: biological catalysts
1. speed up reactions by lowering activation energy EA—the initial investment of energy for starting a reaction 2. very specific—only react on a certain substrate (‘lock & key’) 3. induced fit—enzyme actually changes its shape ii. active site (enzymes provide it, usually a groove on the if organic, called coenzymes ex/vitamins 4. inhibitors—if bind covalently, usually irreversible ex/sarin i. mimic normal substrate (competitive inhibition), ii. bind & cause enzyme to change shape (noncompetitive) 5. allosteric regulation—can inhibit or activate by binding 6. some factors affecting enzymatic activity 1. primary: sequence of amino acids (peptide bonds created) 2. secondary: spatial organization (ex. alpha helix, beta pleated sheet); due to H bonds between backbone, not amino acid side chains. amino acids can be twisted, folded 3. tertiary: shape of entire molecule; chain itself is folded. Level where interactions between R groups most important. Strong covalent bonds between amino acids maintain 3D shape. Example: can have disulfide bridges—from 2 cysteines 4. quaternary: # of chains; >1 chain → 3D structure 5. chaperonins: (chaperone proteins)—assist proper folding of 6, Denaturation: a change in a protein’s 3D shape/conformation due to disruption of H bonds, disulfide bridges, or ionic bonds. Can be due to pH, salt concentration, temp, chemicals, etc. Denatured protein becomes misshapen, and biologically inactive. h. Amino acid sequence of a polypeptide is programmed by a unit of inheritance called a GENE. Genes are made up of DNA, a nucleic acid. a. function: chemical activity & code for information. c. monomer-nucleotides. Nucleotides have 3 components pyrimidines-one ring (ex. thymine, uracil, cytosine) purines- double ring (ex. adenine, guanine) d. important examples: DNA (double strands—held together with H 7. ATP—organic phosphate—adenosine triphosphate a. primary energy transferring molecule in cell i. consists of an organic molecule (adenosine) attached to a b. one of ATP’s three phosphates may split off as an inorganic phosphate c. losing 1 phosphate, ATP becomes ADP; the reaction releases energy

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