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Download Chapter 5: Biological Molecules Molecules of Life • All life made up
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Chapter 5: Biological Molecules Molecules of Life All life made up of four classes of large biological molecules o Lipids, Carbohydrates, Proteins, Nucleic Acids Macromolecules o Large molecules made of thousands of covalently connected atoms Polymer – long molecule made of many similar or identical building blocks Monomer – small building-block o 3 of 4 organic classes are polymers (Carbs, Proteins, & Nucleic acids) Dehydration Reactions Two small molecules covalently bonded together w/ loss of water o Forms polymers, fats, & phospholipids Enzyme – protein that speed up reactions & remains unchanged Hydrolysis Reactions ‘Breaking with water’ Reverse of Dehydration o Breaks polymers into monomers by adding hydrogen & hydroxyl ATP hydrolysis breaks off phosphate releasing energy Lipids Hydrophobic molecules o Mostly hydrocarbons parts (nonpolar covalent bonds) DO NOT form polymers Fats (Triglycerides) o Glycerol (head) w/ 3 Fatty acids (tails) connected via ester linkage o Energy storage molecules o Humans & other mammals store fat in adipose cells Adipose tissue – cushions vital organs & insulates body o Fatty Acids Vary in length (# carbons), location, & # of double bonds Saturated fatty acids – max # of hydrogens (no double bonds) Unsaturated fatty acids – 1+ double bonds present Trans Fat Raises LDL (bad cholesterol) Lowers HDL (good cholesterol) Phospholipid o Major component of all cell membranes o Glycerol w/ phosphate group & 2 fatty acid tails o Amphipathic molecule Hydrophilic head (phosphate) 2 Hydrophobic tails (fatty acids) Steroids o Lipids characterized by carbon skeleton of 4 fused rings o Cholesterol – made in liver Precursor to sex hormones (testosterone & estrogen) & bile salts (digestion aid) Common part of animal cell membrane Transported via lipoproteins Carbohydrates Sugars & polymers of sugars Fuel & building material for cells Monosaccharides (aka simple sugars) o Empirical formula of CH2O Glucose (C6H12O6) most common o Classified by: # of carbons in carbon skeleton Location of carbonyl group Disaccharides o 2 monosaccharides linked to transport sugars in organisms o Sucrose: Fructose/Glucose o Maltose: Glucose/Glucose o Lactose: Glucose/Galactose Polysaccharides (aka Complex Carbs) o Polymers of monosaccharides Few hundred to few thousand Glycosidic linkage connection o Storage & structural roles o Plant Polysaccharides Starch (Amylose & Amylopectin) – energy storage; made of -glucose Surplus starch stored as granules in chloroplasts & other plastids Cellulose – major structural component of cell wall; made of -glucose Glycosidic linkages differ b/c two ring forms for glucose: alpha () & beta () Polysaccharide Digestion Enzymes digesting starch (hydrolyze -linkage) can’t digest cellulose (hydrolyze -linkage) Humans pass cellulose as insoluble fiber Many herbivores have mutualistic relationships w/ microbes that digest cellulose o Animal Polysaccharides Glycogen – energy storage polysaccharide Humans & other vertebrates store glycogen mainly in liver & muscle cells High blood sugar = Insulin (pancreas) released Blood sugar uptaken & glycogen formed Low blood sugar = Glucagon (pancreas) released Glycogen broken down releasing glucose o Chitin Structural polysaccharide found in arthropod exoskeletons & fungal cell walls Nucleic Acids DNA – Deoxyribonucleic acid o Made of genes, which form chromosomes o Direct amino acid sequence of proteins o Has directions for DNA replication RNA – Ribonucleic acid o DNA directs synthesis of messenger RNA (mRNA) = transcription mRNA read by ribosomes to make proteins = translation o rRNA – ribosomal RNA o tRNA – transfer RNA DNA Double Helix o Double helix – 2 polynucleotides spiral around an imaginary axis Backbones run in opposite (5 → 3) directions; antiparallel o DNA bases pair up & form H-bonds T w/ A & G w/ C DNA v. RNA o DNA Directs cell processes Double stranded A, T, G, C Deoxyribose sugar o RNA Protein synthesis Single stranded A, U, G, C (U replaces T) Ribose sugar Evolutionary Tape Measure Sequences of nucleotides in DNA are passed from parents to offspring Molecular biology is used to assess evolutionary kinship 2 closely related species’ DNA is more similar than more distantly related species Proteins Account for over 50% of cell’s dry mass Functions – enzyme, storage, structural support, transport, movement, cellular communications, & defense against foreign substances Polypeptide o Polymer built from set of 20 amino acids o Linked by peptide bonds via dehydration reaction o Each has unique amino acid sequence; can be a few to more than a thousand Amino Acid Structure o -Carbon bonded to: Hydrogen Carboxyl group Amino group Side Chain (R group) – accounts for different properties Structure & Function o Functional protein consists of 1 or more polypeptides coiled, twisted, & folded into a unique shape o Amino acid order determines protein’s 3-D structure, which determines function 4 Levels of Protein Folding o Primary Structure Unique sequence of amino acids Like letters in a word Determined by inherited genetic information (DNA) o Secondary Structure Found in most proteins; made of coils & folds in chain H-bonds form b/w repeating parts of polypeptide backbone helix coils β pleated sheet folds o Tertiary Structure Final folding of individual polypeptide Determined by interactions b/w side chains (R groups) H-bonds, ionic bonds, hydrophobic interactions, & van der Waals interactions Disulfide bridge – strong covalent bonds that reinforce protein structure o Quaternary Structure Results from 2 or more polypeptide chains forming 1 macromolecule Collagen – fibrous protein made of 3 polypeptides coiled like a rope Hemoglobin – globular protein made of four polypeptides (2 alpha & 2 beta chains) Sickle-Cell Disease o Inherited blood disorder o Single amino acid change in protein hemoglobin Amino Acid 6 is Valine instead of Glutamic Acid Alters shape & function Protein Structure o Physical & chemical conditions affect structure, along w/ primary structure Changes in pH, salt, temp, or other environmental factors can cause proteins to unravel o Denaturation – loss of protein’s native structure; becomes biologically inactive Protein Folding o Most go thru several states on way to a stable structure o Chaperonin – protein that assists in proper folding of other proteins Separate proteins from ‘bad’ influences in cytoplasm during folding Protein Examples Fibrous Proteins o Alpha-helix fibrous proteins Alpha-keratin – horns, nails, claws, hooves, hair, fur Elastin – found in arteries, lungs, ligaments, skin, bladder, cartilage o Beta-pleated fibrous proteins Reptiles & birds – scales, feathers, shells, claws Globular Proteins o Irregular shaped ‘glob’ Actin Intrinsic membrane proteins Antibodies Hormones Most blood proteins Enzymes Conjugated Proteins o Proteins with nonproteinaceous group attached Glycoproteins Lipoproteins Metalloproteins Hemoproteins Phytochromes