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Chemistry of Life

microcosm.web.cern.ch. Chemistry of Life. “Life is just a series of chemical reactions.” LECTURE #2 Winter 2011. All living things are composed of chemical components that interact with one another in well-defined ways. Components (elements) of life

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Chemistry of Life

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  1. microcosm.web.cern.ch Chemistry of Life “Life is just a series of chemical reactions.” LECTURE #2Winter 2011

  2. All living things are composed of chemical components that interact with one another in well-defined ways. • Components (elements) of life • Chemistry of those components key to function

  3. south.mpls.k12.mn.us 99% of living things are composed of H, O, N, C Atomic Number = number of protons ina particular element

  4. Composition Elements are substances that can’t be broken down to other particles by ordinary means. An atom is the smallest unit of an element that still retains the properties of that element. • Protons = positive charge • Neutrons = no charge • Electrons = negative charge

  5. Elements are defined by the number of protons in a single atom of that element. • Atoms can lose or gain electrons = ion. • Atoms also occasionally exist with different numbers of neutrons = isotope.

  6. Unbalanced atoms… • Isotope: Atom that has a different number of neutrons • 99% of carbon on Earth is Carbon-12 (6 neutrons, 6 protons) • But there’s also Carbon-13 (7 neutrons) and Carbon-14 (8 neutrons) • Radioisotopes: isotopes that “decay” in a predictable way • Rare. Unstable. • Different weight • Radioactive dating (Carbon-14)

  7. Bonding patterns • Energy seeks its lowest state. (Stable form.) • Atoms do this by completing their “outer electron shell” Result = Atoms with unfilled shells are more likely to bond with other atoms. Importance = Tells us which atoms are likely to form bonds (number, type). Hydrogen (reactive) Helium (inert)

  8. Electron shell examples Wants to bond with 1 other atom Wants to bond with 4 other atoms Wants to bond with 2 other atoms

  9. Types of bonds • Covalent bonding Atoms share electrons to become stable, molecules form! Nonpolar covalent bond = Equal “pull” from all atoms. Polar covalent bond = One atom exerts more force (partial negative charge)

  10. Types of bonds • Ionic bonding • Association where one atom donates 1+ electrons to another atom. • Because each atom isnow an ion (has a positive or negative charge), bonding is a result of mutual attraction.

  11. Table salt is the result of an ionic bond planetgreen.discovery.com belmontfrontporch.wordpress.com

  12. Types of bonds • Hydrogen bonding • A weak association between an electronegative atom and a hydrogen atom that’s already in a covalent bond. • These bonds are very common andeasily broken. • Reason why water has such unique properties!

  13. Water Properties Cohesion = molecules “sticky”Adhesion = attachment of different substances to water • High freezing point = 32 F • Less dense as solid =max number of H bonds formed (ice floats)

  14. Water = “universal solvent” • Solute = What is being dissolved • Solvent = Liquid that dissolves solute • Solution = A mixture of 2+ molecules, atoms or ions that is homogeneous throughout. en.wikibooks.org

  15. Na+Cl- crystal structure Na+Cl- dissociates in H2O

  16. Hydrophobic vs. Hydrophilic • How compounds interact in water… • Hydrophilic = “water loving”  POLAR Has an affinity for water and can dissolve in water - Hydroxyl groups (OH), + or - charges • Hydrophobic = “water fearing”  NONPOLARRepelled by water; don’t mix in aqueous solvent - Hydrocarbons (CH) such as oils

  17. Water and pH H2O H+ OH- pH is a measure of acidity (+) or alkalinity (-) • ACIDIC solutions have low pH, which means there is an abundance of H+ ions  acids donate H+ • BASIC or ALKALINE solutions have high pH, which means an abundance of OH- (hydroxide) ions  bases accept H+ • NEUTRAL solutions (pH=7) have a balance of these ions.

  18. pH is on a LOG SCALE. So something with a pH of 6 has 10 times the concentration of H+ as one with a pH of 7. Eggs Oranges Coffee Bananas

  19. Acids & Bases • Both acids and bases are corrosive/caustic • Damage enzymes, cells, tissues • pH in the body is under homeostatic control • Blood pH = 7.4 • Human cell pH = 7 • Human urine – 4.4 to 8 (usually ~6) • Stomach pH = 1 • Saliva = 6.2 to 7.4 • Buffer = a substance that helps stabilize pH • EX: Antacids that control the acidity of your stomach.

  20. Water Activities

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