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chemistry of life

chemistry of life

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  • 109 elements have thus far been named (92 are naturally occurring; 17 are synthetic). 25 elements are essential to life.
  • Bulk elements - needed in large quantities. [H, C, N, O, P, S, Cl, K, Ca, etc] Trace elements - needed in small quantities. [ex. Iodine is required for the thymus gland to produce its hormones; Zinc is required to produce chlorophyll] A few elements ( arsenic , bromine & tin ) are toxic in large amounts, but may be vital in very small amounts.
  • All carbon atoms have the same number of protons, but they may have differing numbers of neutrons.
  • Since isotopes have differing numbers of neutrons, they have differing masses. Neutrons determine nuclear stability. Atoms with equal numbers of protons & neutrons are most stable. Unstable isotopes tend to break down into more stable forms. When they break down they release radioactive energy. Often one isotope of an element is very abundant & others are rare (99% of carbon isotopes have 6 neutrons).
  • NOTE: some molecules are “diatomic”, consisting of two atoms of the same element. Diatomic molecules include oxygen (O 2 ), nitrogen (N 2 ), hydrogen (H 2 ) and chlorine (Cl 2 ). These diatomic molecules are not considered to be compounds by definition.
  • Lines between the interacting atoms indicate a shared pair of electrons. The compounds seen here are commonly called hydrocarbons because they contain C & H only.
  • Electronegativity - tendency of an atom to attract electrons. Oxygen is highly electronegative. Hydrogen has a low electronegativity. The oxygen atom pulls hydrogen’s negatively charged electrons away from hydrogen’s nucleus an towards its own. Thus, the oxygen atom has a slight negative charge, while both hydrogens have a slight positive charge.
  • Sodium ion (Na + ) = sodium atom that has lost an electron. Chlorine ion (Cl - ) = chlorine atom that has gained an electron.
  • *Hydrogen bonds are individually weak, but a large number of them together will provide a great deal of strength, like the teeth of a zipper. Note: Hydrogen bonds are located between separate water molecules (here we see 4 hydrogen bonds); however, within each water molecule, the H atoms are bonded to the C by covalent bonds!
  • Movement of water from a plant’s roots to its highest leaves depends upon cohesion of water molecules & their adhesion to the plant’s water-conducting tubes. Water’s high heat capacity allows organisms to be exposed to extremes of temperature. Their body fluids heat or cool slowly.
  • Because water has a high heat of vaporization , the body cools off quickly as sweat evaporates from its surface. Because ice is less dense than water, it floats on the surface, forming a cap that retains heat in the water below.
  • Acids have pH values that range below 7.0, with a pH of zero being the most acidic. Bases have pH values that range above 7.0, with a pH of 14 being the most alkaline. Pure water has a pH of 7.0 and is considered to be neutral. * Each unit on the pH scale represents a 10 fold change in H + concentration. Thus, the H+ concentration of soap (pH=10.0) is 100 times greater than that of household ammonia (pH=12.0).
  • Common monosaccharides include: ribose (5 carbon sugar) deoxyribose (5 carbon sugar) glucose - blood sugar (6 carbon sugar) fructose - fruit sugar (6 carbon sugar) galactose (6 carbon sugar) Note: glucose fructose & galactose have the same molecular formula C 6 H 12 O 6 . Thus, they are isomers.
  • Glucose + Fructose  Sucrose (table sugar) + water Because water is formed, sucrose will have 2 less hydrogen atoms & 1 less oxygen atom that glucose & fructose combined. Note: hydrolysis (splitting by adding water) breaks disaccharides apart yielding component monosacchrides. Glucose + Glucose  Maltose Glucose + Galactose  Lactose
  • Common polysaccharides include: cellulose - forms wood & parts of plant cell walls. starch - energy storage form in plants. glycogen - short term energy storage form in animals. cellulose, starch & glycogen are long chains of glucose units; differ in branching patterns chitin - forms the exoskeletons of arthropods & cell wall in many types of fungi. Cellulose is most common organic compound in nature. Chitin is second most common polysaccharide in nature.
  • Number of carbon atoms always much greater than number of oxygen atoms.
  • Note: many more C atoms than O atoms. Saturated fats - fatty acids are saturated with H atoms. There are no double-bonded carbons. Tend to be liquid at room temperature. Unsaturated - fatty acids are not completely saturated with H atoms (thus have 1 or more double bonded carbons). Double bonds cause kinks in the fatty acid tails. Tend to be solid at room temperature. Lipids in plants are less saturated than those in animals.
  • Cortisone is a steroid hormone. Cholesterol is a key component of cell membranes.
  • An amino acid contains a central carbon atom bonded to: a hydrogen atom a carboxyl group (COOH) an amino group (NH 2 ) an R group - differs for each of the 20 biologically important amino acids.
  • Conformation of protein is critical to its function.
  • Antibodies = Function in immunity. Hemoglobin = protein in RBCs that transports oxygen. Insulin & Glucagon = protein hormones that regulate levels of glucose in the bloodstream. Keratin = structural protein found in hair, nails, hooves. Fibrin & thrombin = proteins involved in blood clotting. Enzymes are protein catalysts (speed up chemical reactions without being altered in the process; thus they are reusable).
  • Each nucleotide is composed of: a 5 carbon sugar (ribose or deoxyribose) a phosphate group a nitrogenous base (guanine, cytosine, thymine, adenine or uracil).

Transcript

  • 1. Chapter 2 THE CHEMISTRY OF LIFE
  • 2. A. Matter Material that takes up space. 1. Elements Pure chemical substances composed of atoms. Examples? How many elements exist? How many of these elements are essential to life?
  • 3. Periodic Table of Elements
  • 4. 2. Atom The smallest “piece” of an element that retains the characteristics of that element. Composed of 3 subatomic particles: Protons Neutrons Electrons
  • 5. Characteristics of Subatomic Particles
  • 6. Atomic number # protons in nucleus of an atom (establishes identity of the atom) Since most atoms are electrically neutral, atomic number indicates # of electrons as well. Mass number # protons plus # neutrons in nucleus of an atom
  • 7. How can we determine the number of neutrons in an atom? # neutrons = atomic mass - atomic # Determine # neutrons in a carbon atom (atomic mass = 12; atomic # = 6). # neutrons = 12 - 6 = 6 Do all carbon atoms have the same number of protons? Do all carbon atoms have the same number of neutrons?
  • 8. Isotopes Atoms having the same number of protons, but differing numbers of neutrons. Ex. Carbon isotopes carbon 12 (12 C) → 6 neutrons carbon 13 (13 C) → 7 neutrons carbon 14 (14 C) → 8 neutrons
  • 9. Periodic table information on carbon: Atomic mass given in table is average mass of all the element’s isotopes.
  • 10. 3. Compound A pure substance formed when atoms of different elements bond. The number of atoms of each element is written as a subscript. Examples: CO2 carbon dioxide H2O water CH4 methane C6H12O6 glucose
  • 11. 4. Molecule Smallest piece of a compound that retains characteristics of that compound. The number of molecules is written as a coefficient. Examples: 4CO2 4 molecules of carbon dioxide 2C6H12O6 2 molecules of glucose 6O2 6 molecules of oxygen
  • 12. 5. Chemical Bonds Type of bond formed is determined by the number of valence electrons in the interacting atoms [octet rule]. a) Covalent bonds - form when atoms share electron pairs. can be nonpolar or polar form molecules
  • 13. Nonpolar covalent bonds - electrons are shared equally between atoms. Ex. methane
  • 14. Polar covalent bonds - electrons are drawn more strongly to 1 atom’s nucleus than the other. Form when less electronegative atoms bond with more highly electronegative atoms. Ex. water
  • 15. b) Ionic bonds - form when oppositely charged ions are attracted to each other. stronger than covalent bonds typically form salts Ex. NaCl
  • 16. c) Hydrogen bonds - form when opposite charges on two molecules are attracted to each other. weakest type of bond* Ex. DNA H2O
  • 17. B. The Importance of Water 1. Properties Cohesion - the attraction of water molecules for each other. Adhesion - the attraction of water molecules for other compounds. High heat capacity – takes a great deal of heat to raise the temperature of water.
  • 18. High heat of vaporization - a lot of heat is required to evaporate water. Exists as solid, liquid or gas - solid (ice) is less dense than liquid. 2. Solutions A solution is a mixture of one or more solutes dissolved in a solvent. If solvent is water, then it is an aqueous solution. Water is a strong solvent because it separates charged atoms or molecules.
  • 19. 3. Acids & Bases Acids - substances that add H+ to a solution. Bases - substances that remove H+ from solution. pH scale is measure of acidity/alkalinity based on H+ concentration.
  • 20. C. Major Organic Molecules Molecules that contain carbon in combination with hydrogen. 1. Carbohydrates contain C, H & O [# C ≅ # O] function to store energy & provide support building blocks (monomers) are monosaccharides
  • 21. Monosaccharides simple sugars containing 3 - 7 carbons. C, H, O ratio is 1:2:1
  • 22. Disaccharides simple sugars composed of 2 monosaccharides linked together by dehydration synthesis. Other common disaccharides: maltose (seed sugar) & lactose (milk sugar).
  • 23. Polysaccharides complex carbohydrates made up of hundreds of monomers linked by dehydration synthesis.
  • 24. 2. Lipids contain C, H, O [# C >> # O] do not dissolve in water Triglycerides (fats) composed of glycerol linked to 3 fatty acid chains by dehydration synthesis. function to cushion organs, as insulation & in long-term energy storage (adipose tissue).
  • 25. Phospholipids lipid bonded to a phosphate group major component of cell membranes
  • 26. Sterols lipids that have 4 interconnected carbon rings Ex. Vitamin D, cortisone, estrogen & cholesterol Waxes fatty acids combined with hydrocarbons help waterproof fur, feathers, leaves & fruits
  • 27. 3. Proteins contain C, H, O, N, (S) monomers are amino acids
  • 28. Proteins have a 3-dimensional shape (conformation): primary (1o ) structure - amino acid sequence of polypeptide chain secondary (2o ) structure - coiling & folding produced by hydrogen bonds tertiary (3o ) structure - shape created by interactions between R groups quarternary (4o ) structure - shape created by interactions between two or more polypeptides
  • 29. Examples: antibodies hemoglobin insulin & glucagon keratin fibrin & thrombin spider silk (strongest natural fiber known) enzymes (maltase, pepsin, lipase)
  • 30. 4. Nucleic Acids contain C, H, O, N, P monomers are nucleotides
  • 31. DNA (deoxyribonucleic acid) 5-carbon sugar is deoxyribose nitrogenous bases are A, G, C & T double-stranded helix held together by hydrogen bonds is the genetic material
  • 32. RNA (ribonucleic acid) 5-carbon sugar is ribose nitrogenous bases are A, G, C & U single-stranded enables information in DNA to be expressed