Chapter 1 Molecular Biology Cellular Respiration.pdf

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University of Florida
Biology - Biological Sciences
BSC 3096

Chapter 1 Molecular Biology; Cellular Respiration Tuesday, June 25, 2013 9:51 PM 1. Water a. Solvent chemical reactions take place in b. Ability to hydrogen bond is what allows it to maintain its liquid state in cellular environment c. H-bonding provides strong cohesive force that squeeze hydrophobic molecules away 2. Lipids a. Low solubility in water, high solubility in nonpolar organic solvents b. Six major groups i. Fatty acids 1) Building block for most (NOT ALL) complex lipids 2) Usually contains an even number of carbons, max is 24 3) Saturated have only C-C bonds 4) Unsaturated have at least 1 C=C bond 5) Most fats reach the cell in the form of fatty acids ii. Triacylglycerides 1) Fats and oils 2) Constructed from 3 C backbone called a glycerol attached to three fatty acids 3) Function is to store energy and provide thermal insulation and padding a) Are more efficient at storing energy than carbs and proteins 4) Adipocytes (fat cells) are special cells that contain almost all triacylglycerides iii. Phospholipids 1) Also built from a glycerol backbone but has a polar phosphate group instead of one FA 2) Amphipathic iv. Glycolipids 1) Also built from a glycerol backbone but has one or more carbohydrates instead of a phosphate group or FA 2) Also amphipathic 3) Found in abundance in the membrane of myelinated cells composing the human nervous system v. Steroids 1) Four ringed structures 2) Include hormones, vitamin D, cholesterol vi. Terpenes 1) Vitamin A 2) Strong smelling 3) Major component of resin vii. Eicosanoids 1) Include prostaglandins, thromboxanes, leukotrienes 2) Released from cell membranes as local hormones by oxidizing a fatty acid a) Regulate blood pressure, body temp, smooth muscle contractions 3) Aspirin is commonly used to inhibit synthesis of prostaglandins viii. ix. Lipids are insoluble. They must be transported in the blood via lipoproteins x. Lipoproteins 1) Contains lipid core surrounded by phospholipids and apolipoproteins 2) Classified by their density 3) Apolipoproteins are complexes on the lipoprotein specific to membrane receptors in different tissues used for receptor mediated endocytosis 4) The more protein in the center, the denser it is (HDL) 5) Types of lipoproteins are chylomicrons, VLDL, LDL, HDL 6) 3. Proteins (AKA polypeptides) a. Built from chains of AA linked by peptide bonds b. There are 10 essential AA in humans. We cannot make them c. Amino acids in solution will always carry one or more charges d. Number and sequence of AA in a polypeptide is called primary structure e. Primary structure can twist into α-helix or β-pleated sheet (secondary structures) f. Secondary structures contribute to the conformation of the protein g. α-helix i. h. β-pleated sheet i. Can be parallel or antiparallel ii. i. There are five forces that create tertiary structures i. Covalent disulfide bonds between two cysteine AA on different parts of chain ii. Electrostatic interactions between acidic and basic side chains iii. H bonds iv. Van der Waals forces v. Hydrophobic side chains j. Proline induces turns in polypeptide that disrupts both α-helix and β-pleated sheet formation k. Once a denaturing agent has been removed, the protein will spontaneously refold to its original conformation l. AA sequence plays a key role in conformation of proteins! m. n. Globular proteins act as enzymes o. Structural proteins are made from long polymers and add strength to matrix p. Collagen (main component of connective tissue) i. Adds strength to skin, tendons, ligaments, and bone ii. Most abundant protein in the body q. Microtubules i. Made from globular tubulin r. Glycoproteins i. Proteins with carbs attached ii. Components of plasma membrane s. Proteoglycans i. Proteins that are heavily glycosylated (have lots of carbs attached) t. Cytochromes (example: hemoglobin) i. Proteins that require a prosthetic heme in order to function ii. Membrane bound and generate ATP via electron transport iii. Add color to the cell u. Conjugated protein i. Protein that functions in interactions w/ other chem groups by covalent bonds or by weak interactions 4. Carbohydrates (AKA sugars and saccharides) a. Made from sugar and water b. C(H 2) n c. Essentially all digested carbs that reach body cells have been converted to glucose d. Glucose can exist in chain and ring form, but ring for is heavily favored in aqueous solutions e. Anomer - one of two configurations that a cyclic saccharide can have f. α-glucose i. Hydroxyl group on carbon number 1 and methoxy group on carbon 6 are on opposite sides of the carbon ring ii. g. beta-glucose i. Hydroxyl group and methoxy group are on the same sides of the ring ii. h. Glucose can be stored as the polymer glycogen or converted to fat i. Glycogen i. Branched (α-(1-6) linkage) glucose polymer ii. Found in all animal cells iii. Large amounts are found in muscle and liver cells 1) The liver regulates blood glucose levels and can change glycogen back to glucose and release it into the bloodstream iv. j. Most cells absorb glucose thru facilitated diffusion i. k. Only certain epithelial cells in the digestive tract and proximal tubules of the kidneys can absorb glucose against a concentration gradient via secondary active transport i. Epithelial cells lining the gut need to bring glucose made available from digestion into the body and must prevent the reverse flow of glucose from body to gut. We need a mechanism to ensure that glucose always flows into intestinal cells and gets transported into the bloodstream, no matter what the gut concentration of glucose ii. The blood stream already has a high level of glucose iii. An Na+ gradient is established thru Na+/K+ pump iv. The Na+ ions reenter the cell epithelia, contransporting glucose v. l. Insulin increases the rate of facilitated diffusion of glucose and other monosaccharaides i. m. Plants store glucose as starch and cellulose n. Starch i. Amylose and amylopectin ii. Amylose is an isomer of cellulose that can be branched or unbranched and has the same α linkages as glycogen iii. Amylopectin resembles glycogen but has the a different branching structure (still α) o. Cellulose has β linkages i. p. Animals can only digest α linkages q. Some animals like cows and termites have bacteria in their digestive systems that release an enzyme to digest β linkages 5. Nucleotides a. Made of a five carbon sugar, nitrogenous base, phosphate group b. Common nitrogenous bases are AGCTU c. Nucleotides form polymers to make nucleic acids, DNA & RNA d. Nucleotides are joined to each other by phosphodiester bonds i. Between phosphate group of one nucleotides and 3rd carbon of pentose of the other e. Adenine and thymine form two hydrogen bonds f. Guanine and cytosine form three hydrogen bonds g. The nucleoside is only the sugar and the nitrogenous base h. Other nucleotides: i. ATP, cAMP, NADH, FADH 2 6. Minerals a. Dissolved inorganic ions both inside and outside cell b. Create electrochemical gradients i. This assists transport of substances entering and exiting the cell c. Can also combine with the cellular matrix to give strength d. Can also act as cofactors in proteins 7. Enzymes a. Lower activation energy for biological reaction b. Are not consumed and not permanently altered by the reaction they catalyze c. DO NOT ALTER THE EQULIBIRUM OF A REACTION! JUST REACTION RATE! d. Lock and key theory i. Enzyme will only fit one substrate (the key) ii. Doesn’t explain all enzymes e. Induced Fit model i. Shape of both enzyme AND substrate are altered upon binding ii. Change in shape helps reaction proceed f. Saturation Kinetics i. As the concentration of substrate increases, the rate of the r
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