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Download Chapter 3 - Advanced Biology
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Chapter 3 The Organic Molecules of Life From: http://www.linearwater.com/membranes.htm The cholesterol molecule is extremely important for the stability and function of nerve and muscle membrane because it stabilizes phospholipid chains in their energetic, alpha forms. At the same time, it provides so much energy to the internal hydrocarbon zone of membranes, by spinning around on its own axis, that ions, molecules and charges cannot pass through. It produces membranes that are extremely good insulators - they prevent positive proton pulses from passing through the walls of cells. But cholesterol also fulfills another vital function. By removing the tail section, a large number of hormone molecules are produced in the glands of our bodies that correspond in length to six linear water molecules. With oxygen atoms in several different configurations on the ends, these hormone molecules bind to different organs to control a large variety of functions. Organic Molecules Inorganic chemistry = nonliving world ◦ Water ◦ Salts Organic chemistry = living world ◦ Chemicals that contain carbon and hydrogen (hydrocarbons) ◦ Carbohydrates, lipids, proteins, nucleic acids The Carbon Atom Prokaryotes have about 5,000 different organic molecules! Eukaryotes about 10,000! How can you make so many different molecules all based on carbon? Carbon has 4 valence electrons Can form 4 covalent bonds with other elements. Mostly CHNOPS! Most often, carbon bonds with itself C-C C=C C=C This bond is very stable and can lead to very long chains. C-C-C-C-C-C-C-C-C-C-C-C-C……. C chains can also branch and form rings Carbon can also form isomers Same chemical formula, different arrangement/geometry Leads to different chemical properties The Carbon Skeleton and Functional Groups Carbon chain of an organic molecule = its backbone/skelton ◦ Gives the molecule its shape Functional groups hang off of the carbon skeleton in various places ◦ Largely determines the molecule’s reactivity Functional groups = a specific combination of bonded atoms with specific chemical properties See pg 33 The letter “R” stands for the rest of the molecule the functional group is attached to. ◦ Saves space when you are only interested in the chemistry of the functional group Examples ◦ -OH groups make a carbon chain polar and therefore hydrophilic (soluble in water) Carbon chains by themselves are very nonpolar and therefore hydrophobic (insoluble) ◦ -COOH groups are polar AND weakly acidic One carbon chain can have many functional groups (repeats or unique) They all interact to form a unique chemistry/reactivity for that particular molecule. The Biological Molecules of Cells 4 Main Categories: ◦ ◦ ◦ ◦ Carbohydrates Lipids Proteins Nucleic acids All can be broken down into subunits and reassembled into the molecules your cells need. Those subunits are called monomers monomer+monomer+monomer=polymer Polymers can get very long, like boxcars on a train Dehydration reaction ◦ water removed (OH + H) ◦ Used to hook monomers togetherpolymer Hydrolysis reaction ◦ water added ◦ Used to break down polymermonomers Carbohydrates Monomer = simple sugar (saccharides) Polymer = disaccharides or polysaccharides Used widely in living things for immediate energy Also used in structural roles Monosaccharides ◦ C backbone of 3-7 carbons ◦ Have many polar –OH groups ◦ Soluble in water ◦ Glucose-most widely known C6H12O6 ◦ 2 isomers = fructose & galactose ◦ Other monosaccharides: ribose & deoxyribose Dissacharides ◦ 2 monosaccharides bonded together ◦ Maltose (glucose-glucose) used in brewing beer ◦ Sucrose (glucose-fructose) from sugar beets and sugarcane = table sugar ◦ High fructose corn syrup (HFCS) = commercially modified sucrose to a higher fructose content. Fructose tastes sweeter to humans. “empty” calories??? Polysaccharides - Energy storage ◦ ◦ ◦ ◦ ◦ Short term energy storage Relatively insoluble Stored in cell Plants store as starch Animals store as glycogen (easier to break down quickly for energy) Storage/release controlled by hormones Polysaccharides – Structural ◦ Long, organized polymers can provide structure and support ◦ Cellulose = most common, make up plant cell walls Wood Cotton fibers ◦ Polymers held to each other by hydrogen bonds ◦ Fibers crisscross each other in the cell wall for more strength ◦ Animal digestive systems can’t break down cellulose, but some microbes can Cows, termites ◦ For humans dietary fiber Helps with digestive system health ◦ Chitin = like cellulose, but with different functional group Exoskeletons of shellfish, insects Cell walls of fungi Coats some seeds (protective) Used in wound dressings, cosmetics and some foods Lipids Widely varied, but ALL don’t mix well with water Long nonpolar hydrocarbon chains Lack of polar functional groups “Oil and water don’t mix” Fats and Oils Fats: ◦ Used by animals long-term energy storage Insulation Oils ◦ Plants Long-term energy storage ◦ Animals Secreted by glands Waterproofing skin, hair, feathers Fat and oil monomers = glycerol & fatty acids Glycerol ◦ Has 3 –OH functional groups (polar) Fatty acid ◦ Long chain of just C and H ◦ Carboxyl on one end Each –OH reacts with the carboxyl groups to form a triglyceride Fatty acids ◦ Most contain 16-18 carbons ◦ Can be saturated or unsaturated Saturated: ◦ ◦ ◦ ◦ All single bonds Maximum number of hydrogens possible Tend to be solids at room temp Linked to atherosclerosis cardiovascular disease Trans fats ◦ Partially hydrogenated (a few double bonds) ◦ Found mainly in processed foods ◦ Heart disease Unsaturated: ◦ ◦ ◦ ◦ Has double or triple bonds Fewer hydrogens than saturated Tend to be liquids at room temp Protective against atherosclerosis Monounsaturated and polyunsaturated ◦ Olive oil, canola oil, certain fish Phospolipids Found in cellular membranes Like a triglyceride, except a phosphate (polar) in the place of the 3rd fatty acid Polar head and non-polar tail Arrange themselves in a bilayer ◦ Important to life Steroids Carbon skeleton = 4 fused rings No fatty acid groups Very diverse ◦ Depends on functional groups attached to rings All derived from cholesterol Ex: testosterone & estrogen Proteins Many functions ◦ ◦ ◦ ◦ ◦ ◦ Support Metabolism Transport Defense Regulation Motion Shape and job of a cell depends on what proteins it contains Protein monomers = amino acids 2 functional groups ◦ NH2 (amino) ◦ Carboxyl (acid) R group ◦ Defines amino acid type ◦ 20 different kinds Interaction between amino acids protein folding protein shape protein job Peptide bonds ◦ Attach amino acids to each other ◦ Are polar ◦ Allows H bonds Polypeptide = chain of amino acids Protein = 100+ amino acids in a polypeptide ◦ 100 is small, some proteins have over 33,000! Levels of structure in proteins ◦ ◦ ◦ ◦ Primary-order of amino acids Secondary-alpha helix or pleated sheet Tertiary-overall shape of amino acid chain Quaternary-some proteins, not all Due to multiple proteins working together Tertiary structure then called subunits of main protein Denatured: when a protein loses its shape and ability to function ◦ Heat ◦ Change in pH Most proteins can be described as: ◦ Fibrous Rod-like Keratin, collagen ◦ Globular Rounded and irregular Most enzymes Nucleic Acids DNA and RNA Monomer = nucleotide ◦ A, T (U), C, G ◦ Each made of phosphate, sugar and nitrogen base DNA ◦ ◦ ◦ ◦ ◦ Double stranded Complementary base pairs Deoxyribose ATCG Linked to protein structures Codes for amino acids in a triplet code ◦ Humans: arranged into 20,500 genes 46 chromosomes RNA ◦ Single stranded ◦ Can loop back on itself ◦ 3 types rRNA tRNA mRNA ◦ Ribose U instead of T
