1 / 45

BIOLOGY 189 Foundations of Life Science Spring 2004

BIOLOGY 189 Foundations of Life Science Spring 2004. Chapter 3. The Molecules of Cells . Introduction. Ability to spin a web is genetically programmed … But so are the properties of the silk produced Structure of silk proteins are determined by DNA. Introduction.

benito
Download Presentation

BIOLOGY 189 Foundations of Life Science Spring 2004

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. BIOLOGY 189Foundations of Life ScienceSpring 2004 Chapter 3 The Molecules of Cells

  2. Introduction • Ability to spin a web is genetically programmed … • But so are the properties of the silk produced • Structure of silk proteins are determined by DNA

  3. Introduction • Structure determines function • Elasticity results from coiling and uncoiling of silk fibers • 5 times stronger than steel • Industrial applications • Surgical thread • Fishing line • Bulletproof vests

  4. Introduction • Spider DNA and spider silk represent two of the four classes of molecules in living organisms • Carbohydrates • Lipids • Proteins • Nucleic acids • A nearly infinite variety of molecules can be made from these four simple classes

  5. 1) Organic Compounds • Next to water, compounds containing carbon are the most abundant in an organism • Organic compounds – compounds synthesized by cells and containing carbon • Large diversity of organic compounds, over 2M described. Diversity stems from… • Carbon’s ability to form 4 covalent bonds • Molecules composed only of carbon and hydrogen are called hydrocarbons

  6. Carbon atoms with attached hydrogen atoms can bond together in chains of various lengths • - Lengths and shapes determine function • - Carbon skeleton – the chain of carbon atoms in organic molecules • - Carbon skeletons may or may not be branched, and may / not have multiple bonds • - Isomers – same molecular formula, but different structure

  7. 1) Organic Compounds • Carbon skeletons may be arranged in rings • Ball and stick (3D) models are vastly different from the structural formulas Ethane Cyclohexane

  8. 2) Functional Groups • Functional groups – groups of atoms that usually participate in chemical reactions • Give a compound some of its unique properties • Four common types in biological systems. All are polar due to O or N. Therefore they are usually hydrophilic (water-loving) and soluble • Hydroxyl – appendage to C skeleton • Carbonyl – add a C to the C skeleton • Carboxyl – add a C to the C skeleton • Amino - appendage to C skeleton

  9. 2) Functional Groups

  10. 3) Macromolecules • Macromolecules – gigantic biological molecules • Carbohydrates • Proteins • Lipids • Nucleic acids • Polymers – large molecules consisting of many identical or similar molecular subunits strung together in a chain • Monomers – the units that serve as the building blocks of polymers

  11. 3) Macromolecules • Immense diversity of polymers, and all are made from a list of 40-50 common monomers. Alphabet example • Examples: 20 amino acids, 4 nucleotides • Arrangement / sequence is the key to diversity • Dehydration synthesis – process by which cells link monomers to form polymers • Hydrolysis – process by which polymers are broken into monomers

  12. 3) Macromolecules

  13. 4) Carbohydrates • Carbohydrate – class of molecules ranging from small sugar monomers to very long polymers • Monosaccharide – carbohydrate monomer • The molecular formula of a monosaccharide is usually a multiple of CH2O. Glucose= C6H12O6 • Monosaccharides possess several hydroxyl groups and a carbonyl group

  14. 4) Carbohydrates • Glucose and fructose are isomers and… • This gives these monomers different properties. • Example: Fructose tastes considerably sweeter than glucose

  15. 4) Carbohydrates • C skeleton can vary from 3 to 7 carbons • Pentoses – 5 C • Hexoses – 6 C • Some monosaccharides switch between linear and ring forms in an aqueous solution • Monosaccharides are the main fuel for cellular work. Cells also use C skeletons

  16. 4) Carbohydrates • Disaccharide – a double sugar constructed by a cell, from two monosaccharides. Occurs via dehydration synthesis • Sucrose (table sugar) is made from 1 glucose and 1 fructose

  17. 4) Carbohydrates • The chemical structure of a compound determines its shape, which determines how well it fits into a taste receptor • Compounds that bind more tightly to a sweet receptor are perceived as being sweeter • Artificial sweeteners may bind to other types of taste receptors, leaving an aftertaste

  18. 4) Carbohydrates • Polysaccharides – polymers of a few hundred to a few thousand monosaccharides linked together by dehydration synthesis • Starch – storage polysaccharide in plant roots, ect. that consists entirely of glucose monomers. Coiled / helical • Cells can break starch down as needed to obtain glucose. This is done via hydrolysis in the digestive system • Potatoes, grains, corn and rice are good sources

  19. 4) Carbohydrates • Animals store excess sugar in the form of glycogen • Glycogen – polysaccharide identical to starch, but extensively branched • Stored as granules in liver and muscle cells. These cells hydrolyze glycogen to release glucose • Our digestive system hydrolyzes glycogen in the meat we eat

  20. 4) Carbohydrates • The most abundant organic compound on Earth is cellulose • Cellulose – polysaccharide resembling starch and glycogen, but forms unbranched fibrils supported by hydrogen bonds • Forms plant cell walls; major component of wood • Cannot be hydrolyzed by most animals. Fiber or roughage. Requires microorganisms (cows / termites)

  21. 5) Lipids • Lipids – diverse compounds consisting of C and H atoms linked by nonpolar covalent bonds • Lipids do not include polymers. Exception among macromolecules • Lipids are hydrophobic (water fearing). Insoluble in water and aren’t attracted to water • Example: Salad dressing. Oil is a type of lipid. It separates from vinegar (mostly water) • Also…

  22. 5) Lipids • The feathers of waterfowl are water resistant!! • “Like water off a duck’s back”

  23. 5) Lipids • Fat – large lipid made from two types of smaller molecules: • glycerol • fatty acids • The main function of fat is energy storage. • One gram of fat contains twice the energy of a gram of starch. • 9 calories per gram of fat • 4 calories per gram of carbohydrate or protein

  24. 5) Lipids • Glycerol – alcohol with 3 carbons, each with a hydroxyl group • Fatty acid – molecule consisting of a carboxyl group and a carbon chain with about 15 other carbons. Nonpolar and therefore hydrophobic • Fatty acids link to glycerol via dehydration synthesis • Triglyceride – synonym for fat. Three fatty acid chains linked to glycerol.

  25. 5) Lipids • Fatty acid chains are often different • Unsaturated – fatty acids and fats with double bonds. • Double bonds cause kinks in the carbon chain and prevent the maximum number of H atoms from bonding • Saturated – single bonds, maximum H atoms

  26. 5) Lipids • Kinks prevent molecules from packing tightly together and solidifying at room temperature • Oils are unsaturated fats (corn, vegetable, olive oil). Plant fats are unsaturated • Margarine and some vegetable oils are hydrogenated • Animal fats are saturated (butter and lard) • Health risk (atherosclerosis) due to plaque build-up

  27. 5) Lipids • There are other lipids of importance • Phospholipids – major component of cell membranes. Structurally similar to fats but… • only have two fatty acid tails • contain phosphorous

  28. 5) Lipids • Waxes – consist of one fatty acid linked to an alcohol • More hydrophobic than fats • Natural protective coating • Fruits • Insects • Plants

  29. 5) Lipids • Steroids – lipids with a carbon skeleton of four fused rings • Cholesterol is a common steroid found in animal cells • Starting material for other steroids (sex hormones) • Too much leads to atherosclerosis • Anabolic steroids pose health risks • Mood swings • Cardiovascular problems • Decrease in natural testosterone

  30. 6) Proteins • Protein – biological polymer constructed from amino acid monomers • Extremely diverse and important molecules • Tens of thousands of different proteins in the human body • Each has a specific function

  31. 6) Proteins • Seven classes of proteins. Different structures for different functions • Structural – spider silk, mammal hair, fibers of tendons and ligaments • Contractile - work with structural proteins, provide muscle movement • Storage - ovalbumin (egg whites), source of AAs for developing embryo • Defensive – antibodies, fight infections • Transport - hemoglobin, carries oxygen around the body • Signal - hormones, chemical messengers that coordinate body activities • Enzymes – catalysts – change rate of chemical reactions without being used up in the process. Most important class of proteins. Suffix -ase

  32. 6) Proteins • Protein diversity is based on different arrangements of 20 universal amino acids • Amino acid – has an amino group, a carboxyl group and an R group • R group – variable part of an amino acid • R groups can be polar (hydrophilic) or nonpolar (hydrophobic). This will determine an AA’s properties

  33. 6) Proteins • Cells link amino acids by dehydration synthesis • Peptide bond – connects the carboxyl group of one AA to the amino-group of a second AA • Multiple AAs connected in a chain • Dipeptide • Polypeptide, can be thousands of monomers or more! • Peptide bonds are cleaved by hydrolysis

  34. 6) Proteins • Protein shape determines function • Ribbon model of lysozyme, an enzyme in tears and WBCs • Lysozyme has a globular shape with a groove • Groove fits over surface molecule on bacteria. Lysozyme recognizes target as bacteria, and destroys!

  35. 6) Proteins • Space –filling model of lysozyme • Denaturation – unraveling of polypeptide chain, usually due to • Extreme temperature • Change in pH • Change in salinity • Denaturation alters the specific shape of a protein • As a result the protein loses it’s function (fried egg ex.)

  36. 6) Proteins • Four levels of structure determining a protein’s specific shape • Primary (1°) structure • Secondary (2°) structure • Tertiary (3°) structure • Quaternary (4°) structure • Transthyretin example. Transport protein in blood • It’s primary structure consists of 4 polypeptide chains, each 127 AAs long • Altering hemoglobin’s AA sequence by one AA causes sickle-cell disease

  37. 6) Proteins • Secondary structure of transthyretin consists of… • Alpha helix – coiling of a polypeptide chain • Pleated sheet – folding of a polypeptide chain • These patterns are maintained by H bonds

  38. 6) Proteins • Tertiary structure – overall 3D shape of protein • Two shapes • Globular – helix and sheet • Fibrous - helical • Globular proteins in aqueous solutions are folded so that hydrophobic R groups are on the inside

  39. 6) Proteins • Quaternary structure – overall shape or structure resulting from the bonding interactions among multiple polypeptide chains (subunits) • Transthyretin has 4 identical subunits • Hemoglobin has 4 subunits of 2 different types

  40. 7) Nucleic Acids • Nucleic acids – polymers that serve as blueprints for proteins • DNA – deoxyribonucleic acid. Inherited from parents • RNA – ribonucleic acid • Genes – specific stretches of DNA molecules that program AA sequences (1° structure) of proteins • Genes ultimately determine the 3D structure of proteins, and thus, their function

  41. 7) Nucleic Acids • DNA works in conjunction with RNA • Information from DNA is transcribed into RNA • This information is translated into the 1° structure of proteins • More on this later in the course!

  42. 7) Nucleic Acids • Nucleotides – monomers that make up nucleic acids • 3 parts • Pentose (5-C sugar) • Phosphate group • Nitrogenous base • DNA nitrogenous bases • Adenine (A) • Thymine (T) • Cytosine (C) • Guanine (G) • Same for RNA, except Uracil (U) instead of Thymine

  43. 7) Nucleic Acids • Polynucleotide – polymer formed from nucleotide monomers via dehydration synthesis • To form a polynucleotide the phosphate group of one nucleotide bonds to the sugar of the next monomer • The result is a repeating sugar-phosphate backbone

  44. 7) Nucleic Acids • DNA forms a double helix, RNA is a single polynucleotide • Double helix – two polynucleotide strands wrapped around each other • Nitrogenous bases protrude into the center of the helix from the sugar-phosphate backbone • Nitrogenous bases pair up via H bonds • A pairs with T • C pairs with G

  45. 7) Nucleic Acids

More Related