3.3 Molecules of Life

Objectives Define monosaccharide, disaccharide, and polysaccharide, and discuss their significance to organisms Relate the sequence of amino acids to the structure of proteins Relate the structure of lipids to their functions List two essential functions of nucleic acids

Carbohydrates organic compounds in a ratio of 2 hydrogen atoms to one oxygen atom; the # of carbon atoms varies

Obj 8: Define monosaccharide, disaccharide, and polysaccharide, and discuss their significance to organisms Monosaccharide a monomer of a carbohydrate simple sugars made mostly by green plants have one carbon ring used for energy

Ex. glucose, fructose, galactose, and dextrose these examples are isomers to each other all have same molecular formula – C6H12O6 have different structural formulas – diff. shape

Disaccharide complex sugars two carbon rings formed by combining of 2 monosaccharides in a condensation reaction

Ex. glucose + galactose = lactose (milk sugar) + H2O glucose + glucose = maltose (malt sugar) + H2O glucose + fructose = sucrose (table sugar) + H2O “-ose” ending tells you it’s a sugar

Polysaccharide composed of three or more monosaccharides Ex. 1. glycogen (animal starch) hundreds of glucose monomers strung together in highly branched chains 2. cellulose (plant starch) thousands of glucose monomers linked in long, straight chains So monomer is glucose

Obj 9: Relate the sequence of amino acids to the structure of proteins Amino Acids - the building blocks of proteins there are 20 basic structure is: a central carbon atom bonded to 1. a single hydrogen atom, 2. a carboxyl group (-COOH), 3. an amino group (-NH2), and 4. a functional group (called the R group)

differences in a.a.’s found in their R groups diff R groups of a.a.’s give proteins their shape – diff shapes have different functions (structure related to function) 2 a.a.’s bond to form a dipeptide covalent bond is called a peptide bond is a condensation reaction long strands of a.a.’s called polypeptides

Protein - an organic macromolecule – composed of long strands of polypeptides sequence or order, #, and kind of amino acids will determine the structure (what protein is produced) - temperature can affect the structure (shape), and so function

enzymes - special proteins that act as catalysts in reactions rxns depend on physical fit btwn enzyme and substrate (reactant being catalyzed) – called a lock-and-key model can be affected (& so fail to work) w/ temp or pH change

Obj 10: Relate the structure of lipids to their functions (fats) - large, nonpolar molecules do not dissolve in water have large #’s of carbon-hydrogen bonds store energy efficiently

Fatty Acids unbranched carbon chains (12 to 28 carbons) - have a carboxyl group (-COOH) at one end carboxyl end is polar, so hydrophilic, “water-loving” other hydrocarbon end is nonpolar, so tends not to react w/ water – termed hydrophobic or “water-fearing” - make up most lipids

1) saturated (“full”) each carbon has 4 bonds all single bonds 2 types: 1) saturated (“full”) each carbon has 4 bonds all single bonds 2) unsaturated less than 4 bonds some double bonds

4 types of lipids – 1st 3 contain fatty acids and an alcohol triglycerides – structure: 3 f.a.’s & 1 alcohol (glycerol) function: Saturated vs. Unsaturated saturated have high melting points, and tend to be solid @ room temp. ex. margarine, lard

unsaturated - liquid @ room temp - found in plant seeds and fruits energy source for sprouting plants 2. phospholipids – structure: 2 f.a.’s joined by glycerol function: form 2 layers of cell membrane waterproof barrier for cell insulation

3. waxes – structure: 1 long f.a. chain joined to a long alcohol chain function: highly waterproof protective coating in plants & animals ex. earwax vs. microorganisms

4. steroids – structure: composed of 4 fused carbon rings w/ various functional groups function: needed for normal nerve cell function ex. cholesterol male development (testosterone)

Obj 11: List two essential functions of nucleic acids DNA (deoxyribonucleic acid) – stores genetic information ribonucleic acid (RNA) – transfers info. for building proteins Both DNA & RNA are polymers composed of repeating monomers called nucleotides

4 monomers: adenosine, thymine, guanine, cytosine Have 3 components (parts) a 5-carbon sugar (deoxyribose) a phosphate group a ring-shaped nitrogenous base 4 monomers: adenosine, thymine, guanine, cytosine