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Life: Levels of Organization •Atoms •Molecules •Macromolecules •Organelles •Cells •Tissues •Organs •Organ systems •Organism THE ELEMENTS OF LIFE • ABOUT 20–25% OF THE 92 NATURAL ELEMENTS ON EARTH ARE ESSENTIAL TO LIFE = ESSENTIAL ELEMENTS • • • • NEEDED TO LIVE A HEALTHY LIFE AND REPRODUCE OF THE TOTAL AMOUNT OF NATURAL ELEMENTS ON EARTH - CARBON, HYDROGEN, OXYGEN, AND NITROGEN MAKE UP 96% MOST OF THE REMAINING 4% CONSISTS OF CALCIUM, PHOSPHORUS, POTASSIUM, AND SULFUR TRACE ELEMENTS ARE THOSE REQUIRED BY AN ORGANISM IN MINUTE QUANTITIES Organizational Levels Atom = smallest unit of an element that still retains the chemical & physical properties of that element i.e. really, really, really tiny thing! -composed of: protons = one positive charge, 1 atomic mass unit (1.673x10-24g) electrons = one negative charge, no mass (9.109x10-28g) neutrons = no charge, 1 atomic mass unit each atom is comprised of a nucleus of protons and neutrons + orbiting electrons PERIODIC TABLE OF ELEMENTS -elements are grouped on a Periodic Table of Elements -the elements are grouped according to physical and chemical characteristics -on the chart each element is associated with a letter, an atomic number & an atomic mass IA IIA http://oxford-labs.com/xray-fluorescence/theperiodic-table/ IIIA IVA VA VIA VIIA VIII atomic symbol atomic mass (weight) 7 3 Li e.g. # protons (e-) = 3 # pr+3 + #No 4 = 7 atomic number 39 19 K e.g. # protons (e-) = 19 # pr+19 + #No 20 = 39 Atomic mass = number of protons + neutrons Atomic number = number of protons when the element is electrically neutral ** when neutral, the number of protons and electrons are equal Molecule • particle formed by the union of more than one atom e.g. same kind of atom - O2 e.g. different types of atoms - H20, C6 H12 O6 • • atoms interact with one another through chemical bonds 2 kinds of chemical bonds: • 1. covalent – sharing of electrons between two atoms • 2. ionic bonds – interaction between a +ve and a –ve ion -chemical bonds form through interactions between electrons Molecule • the true definition of a molecule: a molecule consists of two or more atoms held together by covalent bonds • a single covalent bond – or single bond – is the sharing of ONE pair of electrons • denoted with the structural formula H-H • a double covalent bond – or double bond – is the sharing of TWO pairs of electrons • denoted as O=O or C=C ORGANIC MOLECULES 1. carbohydrates 2. lipids 3. proteins 4. nucleic acids • MUST contain carbon, oxygen and hydrogen 1. Carbohydrates: • provide energy to cells • can be stored as reserve energy supply (humans = glycogen) • supply “building materials” to build certain cell structures • e.g. cell wall of plants • water soluble = hydrophilic • characterized H - C - OH (ratio C:H 1:2) • e.g. glucose C6H12O6 sucrose C12H22O12 classified by size: simple sugars – saccharides complex – polysaccharides monosaccharides disaccharides A. Simple carbohydrates • monosaccharides = known as simple sugars • single saccharide subunit in which the # of carbon atoms is low - from 3 to 7 • e.g. 5 carbon sugar = pentose • e.g. 6 carbon sugar = hexose - formula: C:2H:O • monosaccharides found in humans: glucose galactose fructose Monosaccharides: - in aqueous solutions – the monosaccharides are not linear -they form rings -three ways to represent the ring structure of a monosaccharide 3. Simplest form 1. Molecular ring form 2. Abbreviated ring structure A. Simple carbohydrates • disaccharide = two 6-carbon monosaccharides joined through a covalent bond (glycosidic linkage) -forms by a dehydration synthesis reaction -broken up by a hydrolysis reaction e.g. glucose + glucose = maltose e.g. glucose + fructose = sucrose e.g. glucose + galactose = lactose B. Complex carbohydrates: • known as polysaccharides • built of repeating saccharide subunits • polymer: large molecule built of multiple, repeating monomers or “building blocks” • the monomer of the polysaccharide is usually glucose, • can also include galactose or fructose • some serve as storage materials – hydrolyzed into individual monosaccharides – e.g. starch • others serve as structural or building materials – e.g. cellulose Chloroplast Starch granules Amylopectin Amylose (a) Starch: 1 m a plant polysaccharide Mitochondria Glycogen granules Glycogen (b) Glycogen: 0.5 m an animal polysaccharide LIPIDS • MANY TYPES • 1. TRIGLYCERIDES = FATS AND OILS • 2. PHOSPHOLIPIDS • 3. STEROIDS • CHOLESTEROL – ANIMAL CELL MEMBRANES, BASIS FOR STEROID HORMONES • BILE SALTS - DIGESTION • VITAMIN D – CALCIUM REGULATION • ADRENOCORTICOSTEROID HORMONES • SEX HORMONES A. Triglycerides (Fats) • longest lasting, most plentiful energy supply of the human body • “building blocks” = 3 fatty acid chains (hydrocarbons usually from 16 to 24 carbons) PLUS 1 glycerol molecule • the 3 fatty acids are linked onto the glycerol backbone by dehydration synthesis reactions • fatty acids -differ in chain length with each fat -also differ in the location and number of double bonds within the hydrocarbon chains 1. single C bonds - saturated 2. double C bonds - unsaturated monounsaturated: 1 double bond polyunsaturated: 2 or more double bonds • Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds • Unsaturated fatty acids have one or more double bonds B. Phospholipids • similar to fat molecules - glycerol + 2 fatty acids • modified through the replacement of one fatty acid with a phosphate group (slight negative electrical charge) • phosphate gp hydrophilic “head” • fatty acid gps hydrophobic “tails” • when added to water – self-assemble and form a form a phospholipid bilayer – major component of the plasma membrane C. Steroids • backbone is called cholesterol = 4 fused carbon rings • synthesized in the liver • diversity through attached functional groups e.g. testosterone, estrogen, aldosterone, cortisol 3. Proteins • nearly every dynamic function of a living organism depends on proteins •Greek – proteios = “first place” •more than 50% of the dry mass of most cells •numerous roles: • structural – support of cells and tissues • storage - energy source • transport across cell membranes • hormones and their receptors – signaling • chemical messengers - signaling • antibodies - defense • metabolic role - enzymes 3. Proteins •building blocks = amino acids Side chain (R group) carbon Amino group amino acid: 1. carbon atom called an alpha carbon 2. amino group at 1 end of the alphacarbon 3. carboxyl at the other end 4. a hydrogen attached to the alpha carbon 5. an R group attached to the alpha carbon Carboxyl group • the R group give the amino acid a unique physical and chemical character • 22 amino acids available for human protein synthesis – 20 of them are coded for by our DNA • amino acids joined together by a dehydration synthesis reaction forming a peptide bond = between the NH2 of 1 a.a. and the COOH of the next amino acid 2 a.a. dipeptide 3 a.a. tripeptide 4 or more a.a. polypeptide • the three dimensional shape of the polypeptide is CRITICAL to its function • the 3D polypeptide is the protein 4. Nucleic acids • known as DNA, RNA • C,H,O,N,P • building blocks = nucleotides • nucleotide: 5 carbon sugar (pentose) phosphate group (negative charge) located at the 5’ carbon organic base located at the 1’ carbon bases: 5 types: adenine (A) cytosine (C) guanine (G) thymine (T) uracil (U) There are two families of nitrogenous bases Nitrogenous bases Pyrimidines 1. Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) 2. Purines (adenine and guanine) have a sixmembered ring fused to a five-membered ring Sugars Purines Adenine (A) Guanine (G) (c) Nucleoside components Deoxyribose (in DNA) Ribose (in RNA) Sugar-phosphate backbone 5 end 5C 3C • a nucleic acid is a polynucleotide chain • formed by dehydration synthesis •creates a phosphodiester bond between the phosphate group of 1 nucleotide and the sugar of the next one 5C 3C 3 end (a) Polynucleotide, or nucleic acid phosphodiester bond • two major types of nucleic acids: 1. RNA 2. DNA A. DNA double chain = double helix bases: A, C, G and T 2 chains held by hydrogen bonds between the bases bases pair up in a complementary fashion A=T C G B. RNA single chain bases: A, C, G and uracil (U) in place of T 3 major types: mRNA tRNA rRNA HOCH2 O OH H H OH OH ribose HOCH2 O OH H H OH H deoxyribose c. ATP individual nucleotides can have metabolic functions ATP is the major source of potential energy for cells ATP = adenosine triphosphate (adenosine = adenine + ribose sugar)