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BSC 2010 - Exam I Lectures and Text Pages • I. Intro to Biology (2-29) • II. Chemistry of Life – Chemistry review (30-46) – Water (47-57) – Carbon (58-67) – Macromolecules (68-91) • III. Cells and Membranes – Cell structure (92-123) – Membranes (124-140) • IV. Introductory Biochemistry – Energy and Metabolism (141-159) – Cellular Respiration (160-180) – Photosynthesis (181-200) The Chemistry of Carbon (Ch. 4) • Carbon can bond to carbon: and form long chains or ring structures • Carbon can bond: to many different functional groups. Carbon—The Backbone of Biological Molecules • All living organisms – Are made up of chemicals based mostly on the element carbon Figure 4.1 Carbon atoms can bond to four other atoms • Carbon has four valence electrons • This allows it to form four covalent bonds with a variety of atoms, and to form large complex molecules. Molecular Diversity Arising from Carbon Skeleton Variation • Carbon chains – Form the skeletons of most organic molecules – Vary in length and shape H H H H C C C H H H H Propane H H C H H H H H H H (b) Branching H C C C C H H C C C H H H H H H H H 2-methylpropane Butane (commonly called isobutane) H H H H H H H H (c) Double bonds H H C C C C H C C C C H H H H H 1-Butene 2-Butene H H H H C H H C C H C H (d) Rings H C C H H C C H H C C C (a) Length Figure 4.5 A-D H H H C C H H H Ethane Cyclohexane Benzene The electron configuration of carbon Gives it covalent compatibility with many different elements Figure 4.4 Hydrogen Oxygen Nitrogen Carbon (valence = 1) (valence = 2) (valence = 3) (valence = 4) H O N C Hydrocarbons are molecules consisting of only carbon and hydrogen • Hydrocarbons – Are found in many of a cell’s organic molecules Fat droplets (stained red) Figure 4.6 A, B (a) A fat molecule 100 µm (b) Mammalian adipose cells Functional groups = chemically reactive groups of atoms within a molecule – Give organic molecules distinctive chemical properties Estradiol OH CH3 HO Female lion OH CH3 CH3 O Figure 4.9 Male lion Testosterone Functional Groups Engage in Chemical Reactions • Six functional groups are important in the chemistry of life – Hydroxyl -OH; alcohols – Carbonyl >CO; aldehydes and ketones – Carboxyl -COOH; carboxylic (organic) acids – Amino –NH2; amines – Sulfhydryl -SH; thiols – Phosphate –OPO32-; organic phosphates BSC 2010 - Exam I Lectures and Text Pages • I. Intro to Biology (2-29) • II. Chemistry of Life – Chemistry review (30-46) – Water (47-57) – Carbon (58-67) – Macromolecules (68-91) • III. Cells and Membranes – Cell structure (92-123) – Membranes (124-140) • IV. Introductory Biochemistry – Energy and Metabolism (141-159) – Cellular Respiration (160-180) – Photosynthesis (181-200) Macromolecules – Structure and Function (Ch. 5) Another level in the hierarchy of biological organization is reached when small organic molecules are joined together. Macromolecules are large molecules composed of smaller molecules, and they can be very complex in structure. Figure 5.1 Macromolecules – Structure and Function (Ch. 5) 4 main classes of carbon-based molecules necessary to life 1. Carbohydrates – sugars and their polymers 2. Lipids – diverse group of nonpolar molecules 3. Proteins – polymers of amino acids 4. Nucleic Acids –polymers of nucleotides Most macromolecules are polymers, built from monomers Three of the classes of life’s organic molecules are polymers – Carbohydrates – Proteins – Nucleic acids A polymer is a long molecule consisting of many similar building blocks called monomers The Synthesis of Polymers • Monomers form larger molecules by condensation reactions called dehydration reactions HO 1 3 2 H Unlinked monomer Short polymer Dehydration removes a water molecule, forming a new bond HO Figure 5.2A 1 2 H HO 3 H2O 4 H Longer polymer (a) Dehydration reaction in the synthesis of a polymer The Breakdown of Polymers • Polymers can disassemble by – Hydrolysis HO 1 2 3 4 Hydrolysis adds a water molecule, breaking a bond HO 1 2 3 H Figure 5.2B (b) Hydrolysis of a polymer H H2O HO H Carbohydrates Carbohydrates include both sugars and their polymers Carbohydrates serve as immediate fuel, energy storage, and building material. Sugars • Monosaccharides – the monomers of carbohydrates – Are the simplest sugars – Can be used for fuel – Can be converted into other organic molecules – Can be combined into polymers Examples of monosaccharides Triose sugars Pentose sugars (C3H6O3) (C5H10O5) H O H Aldoses C O H O C C OH H C OH H C OH H C OH H C OH HO C H C OH H H C OH H H H H C H C OH H HO C H C OH HO C H H C OH H C OH H C OH H C OH H H Glucose Galactose H C OH H C O H C OH H C OH C O O C OH H C OH HO H H C OH H C OH Dihydroxyacetone H C OH H C OH H H C OH H Ribulose O C H Ribose Ketoses H C Glyceraldehyde Figure 5.3 Hexose sugars (C6H12O6) C H H Fructose Monosaccharides May be linear, or can form rings O H 1C H HO 2 3 C 6CH OH 2 OH H C H 4 H H H C 5 5C 6 C H OH 4C OH OH OH O 5C H H OH C 6CH OH 2 3 C H 2C O H H 4C 1C CH2OH O OH H OH 3C 6 H 1C H 2C 4 HO H OH 3 OH H H 1 2 OH OH H H O 5 OH OH H Figure 5.4 (a) Linear and ring forms. Chemical equilibrium between the linear and ring structures greatly favors the formation of rings. To form the glucose ring, carbon 1 bonds to the oxygen attached to carbon 5. Disaccharides = dimers • Disaccharides – Consist of two monosaccharides – Are joined by a glycosidic linkage Examples of disaccharides (a) Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide. CH2OH CH2OH H O H OH H OH HO H H H HO H OH H OH H H OHOH H O H OH H CH2OH H 1–4 1 glycosidic linkage HO 4 O H H OH H OH O H OH H H OH OH H2O Glucose Glucose CH2OH H (b) Dehydration reaction in the synthesis of HO sucrose. Sucrose is a disaccharide formed from glucose and fructose. Notice that fructose, though a hexose like glucose, forms a five-sided ring. Figure 5.5 O CH2OH O H OH H H CH2OH H OH HO CH2OH O H H H HO CH2OH OH OH Maltose H O H OH H 1–2 glycosidic 1 linkage H Fructose 2 H H CH2OH OH H OH Sucrose H HO O HO H2O Glucose CH2OH O Polysaccharides – polymers • Polysaccharides – Are polymers of sugars – Serve many roles in organisms – May be 100s to 1000s of monomers Storage Polysaccharides • Starch Chloroplast – Is the major storage form of glucose in plants – Is a polymer consisting entirely of glucose monomers Starch 1 m Amylose Amylopectin Figure 5.6 (a) Starch: a plant polysaccharide Storage Polysaccharides • Glycogen – Consists of glucose monomers – Is the major storage form of glucose in animals Mitochondria Giycogen granules 0.5 m Glycogen Figure 5.6 (b) Glycogen: an animal polysaccharide Structural Polysaccharides - Cellulose H – Is a polymer of glucose CH2O H O H OH H H 4 H – Has different glycosidic linkages than starch CH2O H H O OH H 4 1 OH H HO H C H OH HO O OH glucose H C OH HO C H H C OH H C OH H C OH H OH glucose (a) and glucose ring structures CH2O H O CH2O H O HO 4 1 OH O 1 OH 4 O 1 OH OH OH CH2O H O CH2O H O O 4 1 OH O OH OH (b) Starch: 1– 4 linkage of glucose monomers CH2O H O HO Figure 5.7 A–C OH CH2O H O OH O 1 4 OH O OH OH O OH O O CH2O CH2O OH OH H H (c) Cellulose: 1– 4 linkage of glucose monomers OH Cellulose – Is a major component of the tough walls that enclose plant cells Cell walls Cellulose microfibrils in a plant cell wall Microfibril About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. 0.5 m Plant cells Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. Figure 5.8 OH CH2OH OH CH2OH O O O O OH OH OH OH O O O O O O CH OH OH CH2OH 2 H CH2OH OH CH2OH OH O O O O OH OH OH OH O O O O O O CH OH OH CH2OH 2 H CH2OH OH OH CH2OH O O O O OH OH OH O O OH O O O O CH OH OH CH2OH 2 H Glucose monomer Cellulose molecules A cellulose molecule is an unbranched glucose polymer. Cellulose • Cellulose is difficult to digest – Cows have microbes in their stomachs to facilitate this process Figure 5.9 Chitin – an animal structural polysaccharide – Is found in the exoskeleton of arthropods – Can be used as surgical thread CH2O H O OH H H OH H OH H H NH C O CH3 (a) The structure of the (b) Chitin forms the exoskeleton of arthropods. This cicada chitin monomer. is molting, shedding its old exoskeleton and emerging Figure 5.10 A–C in adult form. (c) Chitin is used to make a strong and flexible surgical thread that decomposes after the wound or incision heals. Lipids • Lipids, a diverse group of hydrophobic molecules – Are the one class of large biological molecules that do not consist of polymers – Share the common trait of being hydrophobic – Are fats, oils, waxes and other biologically important molecules Fats • Fats, oils and waxes – Are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids H H C O C OH HO H C OH H C OH H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H Fatty acid (palmitic acid) H Glycerol (a) Dehydration reaction in the synthesis of a fat Ester linkage O H H C O C H C H O H C O C O H C H Figure 5.11 O C H C H H C H C H H H C H C H H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H (b) Fat molecule (triacylglycerol) H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H H C C H H H C H H C H H C H H C H H C H H C H H C H H H C H H H C H H H C H H • Fatty acids – Can be saturated or unsaturated – Vary in the length and number and locations of double bonds they contain Saturated fatty acids – Have the maximum number of hydrogen atoms possible – Have no double bonds Stearic acid Figure 5.12 (a) Saturated fat and fatty acid Unsaturated fatty acids - Have one or more double bonds - and are thus not “saturated” with the maximum number of hydrogens Oleic acid Figure 5.12 (b) Unsaturated fat and fatty acid cis double bond causes bending Phospholipids • Phospholipids (major part of membranes) – Have only two fatty acids – Have a phosphate group instead of a third fatty acid Phospholipid structure – Consists of a hydrophilic “head” and hydrophobic “tails” (amphipathic) CH2 + N(CH ) 3 3 Choline CH2 O O P O– Phosphate O CH2 CH O O C O C CH2 Glycerol O Fatty acids Hydrophilic head Hydrophobic tails Figure 5.13 (a) Structural formula (b) Space-filling model (c) Phospholipid symbol Cell Membranes • The structure of phospholipids – Results in a bilayer arrangement found in cell membranes WATER Hydrophilic head WATER Hydrophobic tail Figure 5.14 Steroids – lipids characterized by four fused carbon rings • One steroid, cholesterol – Is found in cell membranes – Is a precursor for some hormones H3C CH3 CH3 Figure 5.15 HO CH3 CH3 Steroid Hormones – important chemical messengers • Cholesterol is the precursor to many important hormones: estrogen, testosterone, and progesterone. • Testosterone is the major anabolic steroid, leads to muscle formation, plays a role in sexual drive in the brain. Testosterone can be converted to estrogen, which signals cells to divide. Steroids are also important in bile acids. Prostaglandins • non-steroid lipid-based hormones • important to the inflammatory response and pain. • important in the birth process. • precursor- arachidonic acid.