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Large Biological Molecules

Large Biological Molecules. Chapter 5. Fuel for Living Systems. Large molecules are important for the basic processes of life Grouped into 4 classes of organic compounds Carbohydrates* Lipids Proteins* Nucleic acids* Important to know how these are made, stored, and destroyed

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Large Biological Molecules

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  1. Large Biological Molecules Chapter 5

  2. Fuel for Living Systems • Large molecules are important for the basic processes of life • Grouped into 4 classes of organic compounds • Carbohydrates* • Lipids • Proteins* • Nucleic acids* • Important to know how these are made, stored, and destroyed • Also, structure and function * are considered macromolecules

  3. Polymers • Chain of similar repeating units linked by covalent bonds • E.g CAT-CAT-CAT-CAT=CAT-CAT or the alphabet • Carbs, proteins, and nucleic acids are examples • The similar repeating units are called monomers • E.g CAT or any letter of alphabet • Joined and broken by reversible reactions • Enzymes can speed the reaction • E.g digestion: cells need organic molecules broken down so can be absorbed after which they can be rebuilt

  4. Polymers Making polymers Breaking polymers • Dehydration reaction • Links monomers • Loss of water for each monomer added • Forms a covalent bond • Hydrolysis reaction • Breaks polymers • Addition of water for each broken bond 1 2 4 3 4 1 2 3 1 4 2 3 1 2 3 4

  5. Examples of Polymers • Small molecules are ordered to dictate life • DNA is a polymer composed of 4 monomers (nucleiotides) • Creates variation based on arrangement • Proteins are polymers from 20 different amino acids (AA’s) • Sequence variation separates humans from flowers and individuals from individuals

  6. Carbohydrates • Simple sugars and polymers of simple sugars • Sugars are broken down based on the number of polymers • Monosaccharides • Disaccharides • Polysaccharides • Each is joined by a dehydration reaction • Polymers of sugar are actually what is generally considered a carbohydrate or starchy food

  7. Monosaccharides • Glucose is most common • Major nutrient for cells • Respiration, fuel for cellular work, and raw material • Trademarks of sugars • Molecular repeating unit of CH2O- • Carbonyl and hydroxyl functional groups • 3-7 carbons long • Hexoses (6 carbons, e.g glucose and fructose) • Pentoses (5 carbons, e.g ribose and dioxyribose) • End in “-ose”

  8. Glucose vs Fructose Also are examples of what?

  9. Disaccharides • 2 monosaccharides joined by a covalent bond • Result of dehydration reaction • Form a glycosidic bond/linkage • Maltose • glucose + glucose • Whoppers, malts, beer • Sucrose • Glucose + fructose • Table sugar • Plant sap • Lactose • galactose + glucose

  10. Polysaccharides • Multiple glycosidic linkages • Storage material until needed • Hydrolysis will break apart to provide sugars to cells • Building materials for cell protections • 4 types • Starch • Glycogen • Cellulose • Chitin

  11. Polysaccharides For Storage • Starch • Polymer of many glucose monomers • Plants use as storage • Form of plastids • Stockpiled glucose = stored E • E.g potatoes, grains, wheat, and corn • Glycogen • More branched polymer of glucose • Vertebrate storage in liver and muscles • Hydrolyzed when sugar is needed • Not good for long term because depleted quickly

  12. Cellulose • Cell wall of plant cells • Most abundant organic compound on Earth • Polymer of glucose with different linkages • Straight molecule, grouped to form microfibrils = strong • Major component of paper and only of cotton • Most animals can’t hydrolyze • Undigested, stimulates GI tract through abrasion to stimulate mucous secretion • Most fresh fruits, vegetables, and whole grains • Insoluble fiber on packages

  13. Chitin • Composes arthropod exoskeletons • CaCO3 covers body and hardens • Molted off and commonly eaten as Ca2+ source • Cell walls in fungi • Used for surgical thread • Dissolvable stitches

  14. Lipids • ‘Grab bag’ of molecules • Not true polymers • Not really big enough to be macromolecules • All mix poorly with water due to hydrophobic nature (hydrocarbon chains) • Form ester linkages • 3 types • Fats • Phospholipids • Steroids

  15. Fats • Glycerol (alcohol w/ 3 carbons) and fatty acids (16-18 carbons and carboxyl end) • Hydroxyl and carboxyl linkage = ester linkage (triglyceride) • Can be saturated or unsaturated • Hydrogenated vegetable oils • Unsaturated synthetically to saturated by adding hydrogens • Peanut butter and margarine to prevent separation • Trans fats when conversion changes conformation of double bond • Necessary for energy storage (hydrogen bonds) • More compact, better for mobility • Adipose storage • Cushions vital organs and insulates

  16. Saturated All single bonds with H Most animal fats Solid, close bonds; e.g butter Unsaturated Carbon carbon double bonds Most plant and fish fats Liquid, can’t bind close = bend; e.g olive oil Saturated versus Unsaturated Chains

  17. Phospholipids • Makes up cell membranes • Glycerol with 2 FA’s and 1 phosphate (negative charge) • Hydrocarbons make hydrophobic (form tails) • Phosphate and attachment are hydrophilic (form heads) • Bi-layered to protect hydrophobic from water

  18. Steroids • Lipids with 4 fused rings • Synthesized from cholesterol, common in animal cell membranes • Precursor to sex hormones • Synthetic variants • Anabolic steroids (Testosterone)

  19. Proteins • Necessary for almost anything living organisms do • Know types and functions from table 5.1 • Enzymes regulate metabolism by acting as catalysts • Speed reactions w/o being consumed • Unique 3D shapes • Formed from polypeptides (polymers of amino acids) • 20 AA’s, same set for all • Protein = 1+ polypeptide folded and coiled into specific 3D shape

  20. Amino Acid Monomers • Common structure • Carboxyl and amino group • α-carbon is middle with H and R group (variable) • Determines specific AA from fig. 5.17 • Side chains grouped by properties • Nonpolar, hydrophobic • Polar, hydrophilic • Acidic, (-) charge b/c carboxyl group • Basic, (+) charge b/c amino group • Charges = hydrophilic • Polymers formed by peptide bonds

  21. Structure and Function • Polypeptides ≠ protein • AA sequence does • 4 levels of structure • 1°-seq of AA, determined by genes • 2°-repeated coils or folds for overall shape • H-bonds b/w carboxyl and amino backbone • α-helix = H bonds b/w 4th AA • ß-pleated sheet = 2+ regions of H bonds • 3 °- interactions b/w side chains • Hydrophobic interaction = side chains cluster in • Disulfide bridges = -SH side chain interactions • 4°-overall structure of 2+ polypeptides

  22. Protein Structure and Function • Polypeptides ≠ protein • 1°: genes decide • 2°: H-bonds b/w carboxyl and amino • α-helix: 4th AA • Β-sheet: 2+ regions of side by side H-bonds • 3°: hydrophobic side chains and disulfide bridges • 4 : 2+ polypeptides

  23. Changing Protein Structure • Sickle cell • Single AA substitution in hemoglobin • Abnormal shape RBC’s that clogs vessels • Denaturation • Proteins unravel and lose shape • pH, [salt], temp, and other effects can cause • Inactivates proteins • Removing agents might reverse • Misfolding • Accumulate and cause detrimental problems • E.g Alzheimer’s and Parkinson’s disease

  24. Often times unfolding exposes hydrophobic areas to the aqueous solutions surrounding the protein Aggregates to protect itself Protein Misfolding

  25. Nucleic Acids • Polymers of nucleotides (polynucleotides) • Blueprint for proteins to control all of cellular workings • Control of reproduction • DNA RNA proteins • Central dogma of molecular biology • Occurs in ribosomes • Monomer is a nucleotide • Structure consists of 3 components • Nitrogenous base • 5 carbon sugar • Phosphate group

  26. Nucleotide • Nitrogenous base • Pyrimidine = a 6 member carbon and nitrogen ring • cytosine (C), thymine (T), uracil (U) • Purines = 6 member carbon ring fused to a 5 member ring (smaller name, bigger structure) • adenine (A) and guanine (G) • DNA – C, T, G, and A • RNA – C, U, G, and A • 5 Carbon sugar • Ribose • Deoxyribose (missing oxygen)

  27. Nucleotide Polymers • Phosphodiester linkage = phosphate joins sugars of 2 nucleotides • For backbone of DNA • Phosphate on 5’ carbon joins hydroxyl on 3’ carbon • DNA codes 5’ -3’ • Sequence of bases unique to each gene • Linear order of nitrogenous bases in a gene specifies AA sequence (which level of structure ?) • Start codon • ATG and AUG = DNA and RNA • Stop codon • UAG, UAA, UGA

  28. Double Helix • 1st proposed by Watson and Crick • Sugar-phosphate backbones are antiparallel • Nitrogenous bases face in and H-bonds hold them together • 2 strands are complementary • Binding specific • A binds w/ T • G binds w/ C

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