Chapter 2: The Chemistry of Life

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Chapter 2 The Chemistry of Life

• Biology I

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Atom

• The smallest unit of matter that cannot be broken
  down by chemical means
• Made of 3 types of particles
• Electrons (-)
• Protons ()
• Neutrons (no charge)

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Element

• A pure substance made up of only
  one kind of atom
• Equal number of electrons and protons
• Elements differ from one another by the number of
  protons
• Hydrogen has 1 proton,1 electron
• Oxygen has 8 protons, 8 electrons

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Isotope

• Different numbers of neutrons of the same element
• Carbon-12
• 6 protons, 6 electrons, 6 neutrons
• Carbon-13
• 6 protons, 6 electrons, 7 neutrons
• Carbon-14
• 6 protons, 6 electrons, 8 neutrons

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Periodic Table of Elements

• There are more than 100 known elements
• Each is represented by a 1, 2, or 3 letter symbol

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Chemical Bonding

• Compound a substance made of the joined atoms of
  two or more different elements
• Example when sodium (Na) binds to chlorine atoms
  (Cl) the result is sodium chloride (NaCl) table
  salt!

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Covalent Bonds

• Formed when two or more atoms SHARE electrons to
  form a molecule
• Molecule a group of atoms held together by
  covalent bonds

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Hydrogen Bond

• A weak chemical attraction between polar
  molecules
• Example water
  molecules

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Polar versus Nonpolar Compounds

• Polar compound a compound whose molecules have a
  negative charge on one side and a positive charge
  on the other
• Nonpolar compound a compound whose electrons are
  equally distributed among its atoms

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Ionic Bond

• A bond formed between ions of opposite charges
• Ion an atom or molecule that has gained or lost
  one or more electrons
• Ions therefore have an electrical charge

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Ionic Bonds
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Water in Living Things

• Nearly 70 of your body is water!
• 2/3 of the molecules in your body are water
  molecules!
• Why is water sooooooooo important?

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Water Stores Energy

• Water absorbs heat more slowly and retains this
  energy longer than many other substances do
• Sweat water helps cells maintain homeostasis

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Water Cohesion

• Cohesion an attraction between substances of the
  same kind
• Surface tension water (and other liquids) form
  thin films and drops

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Water Adhesion

• Adhesion an attraction between different
  substances
• Capillary action water molecules move upward
  through a narrow tube (ie a plant stem). The
  attraction of water to the walls of the tube
  sucks the water up more strongly than gravity
  pulls it down

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Aqueous Solutions

• Solution a mixture in which one or more
  substances are evenly distributed in another
  substance
• Many important substances in the body have been
  dissolved in blood or other aqueous solutions (ie
  sugar needs to be dissolved in water to be
  delivered to your cells)

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Water Polarity

• Enables many substances to dissolve in water
• Ionic compounds and polar molecules dissolve best
  in water
• Nonpolar molecules do not dissolve well in water
  (ie oil)

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Acids and Bases

• Water bonds are strong but they can break
• Forming
• H (hydrogen ions) and OH- (hydroxide ions)

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Acids

• Acids compounds that form hydrogen ions (H)
  when dissolved in water
• The concentration of
  hydrogen ions in the
  solution is increased above
  that of pure water

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Bases

• Bases compounds that reduce the concentration of
  hydrogen ions when dissolved in water
• Increase the hydroxide
  ion concentration (OH-)

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pH Scale

• Based on the concentration of hydrogen ions in
  solutions
• pH between 0 and 14
• Each whole number represents a factor of 10 on
  the scale for example, a solution with pH of 5
  has 10X as many hydrogen ions as one with a pH
  value of 6

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pH Scale

• Pure water has a pH value of 7
• Acidic solutions lt 7
• Basic solutions gt 7

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Chemistry of Cells

• Most matter in your body that is not water is
  made of organic compounds
• Organic compounds contain carbon atoms that are
  covalently bonded to other elements

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Chemistry of Cells

• Organic compounds found in living things that
  make cell function possible
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids

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Carbohydrates
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Carbohydrates

• Organic compounds made of carbon, hydrogen and
  oxygen atoms 121
• Key source of energy, found in most foods
• Monosaccharides the building blocks of
  carbohydrates, simple sugars

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Carbohydrates

• Simple sugars glucose (C6H12O6) and fructose
• Glucose is a main source of energy in cells
• Disaccharides double sugars formed when two
  monosaccharides are joined
• Polysaccharides chains of 3 or more
  monosaccharides (ie starch)

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Carbohydrates

• Polysaccharides as storehouses of the energy
• Starch made by plants
• Glycogen made by animals
• Cellulose a polysaccharide that provides
  structural support for plants humans cannot
  digest it

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Lipids

• Nonpolar molecules that are not soluble or mostly
  insoluble in water
• Fats and Oils
• Phospholipids
• Steroids
• Waxes

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Fats and Oils

• Lipids that store energy
• Contain 3 fatty acids
  bonded to a glycerol
  
  molecule backbone
• Glycerol a 3-carbon organic molecule
• Fatty acid a long chain of carbon atoms with
  hydrogen atoms bonded to them

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Saturated Fatty Acids (Saturated Fats)

• All of the carbon atoms in the chain are bonded
  to 2 hydrogen atoms
• Most animal fats (butter, lard grease)
• Most are solid at room temperature

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Unsaturated Fatty Acids (Unsaturated Fats)

• Some of the carbon atoms are linked by a double
  covalent bond, each with only 1 hydrogen atoms,
  producing kinks in the molecule
• Most plant oils, i.e. olive oils, and some fish
  oils
• Most are liquid at room temperature

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Hydrogenated Vegetable Oils (Trans Fats)

• Naturally unsaturated fatty acids that have been
  saturated artificially by the addition of
  hydrogen atoms
• Margarine and vegetable
  shortening are therefore
  generally
  solid at room
  temperature

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Saturated versus Unsaturated
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Hydrogenation
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Phospholipids

• Important part of the structure and function of
  cell membranes
• Glycerol
• 2 fatty acids
• A phosphate group
• Make up the lipid bilayer of cell membranes
• Hydrophilic and hydrophobic

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Steroids and Waxes

• Steroids include cholesterol, found in animal
  cell membranes
• Steroids occur in animals in hormones
• A four-ring structure, one with five carbons and
  three with six carbons in the rings

• Waxes are used to coat and protect things in
  nature.
• Bees, plants, your ears!

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Proteins

• Large molecules formed by linked smaller
  molecules called amino acids
• Amino acids the building blocks or proteins
• 20 different amino acids are found in proteins
• Some are polar, some are nonpolars some are
  electrically charged, some are not

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Proteins

• Proteins fold into compact shapes, determined in
  part by how the proteins amino acids interact
  with water and one another

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Proteins

• Many functions of proteins!
• Enzymes
• Structural proteins
• Antibodies
• Specialized proteins

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Nucleic Acids

• Long chain of smaller molecules called
  nucleotides
• Nucleotides have 3 parts
• Sugar
• Base
• Phosphate group

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Nucleic Acids

• DNA deoxyribose nucleic acid
• Stores hereditary information
• 2 strands of nucleotides
• Sugar deoxyribose

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Nucleic Acids

• RNA ribonucleic acid
• Many key roles in the manufacture of proteins
  can also act as a enzyme, promoting chemical
  reactions
• 1 strand of nucleotide
• Sugar ribose

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ATP

• Adenosine triphosphate
• A single nucleotide with
  2 extra energy-storing
  phosphate groups
• When food is broken down inside cells, some of
  the energy is stored temporarily as ATP cells
  need it to function!

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Energy and Chemical Reactions

• Energy the ability to more or change matter
• Energy can be stored or released by chemical
  reactions
• Chemical reaction a process in which chemical
  bonds between atoms are broken and new ones are
  formed, producing one or more new substances

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Energy and Chemical Reactions

• Reactants the starting materials for chemical
  reactions
• Products the newly formed substances
• Reactants ? Products
• ? means changes to or forms
• NaCl ? Na Cl-

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Energy in Chemical Reactions

• Energy is either
  absorbed or released
• Water freezes
  the formation of
  
  ice crystals causes
  
  heat energy to be
  released
• Ice melts absorbs heat from the environment

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Activation Energy

• The energy needed to start a chemical reaction
• A chemical push that starts a chemical reaction

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Enzymes

• Substances
  that increase
  the speed
  of
  chemical
  reactions
  most are
  
  proteins
• Catalysts substances that reduce the activation
  energy of a chemical reaction

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Enzymes

• Help organisms maintain homeostasis
• Without enzymes some cell processes would take
  too long!

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Enzyme Specificity

• Substrate a substance on which an enzyme acts
  during a chemical reaction
• Enzymes only act on specific substrates
• Active site the site on an enzyme that attaches
  to the substrate

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Enzyme Specificity
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Factors in Enzyme Activity

• Any factor that changes the shape of an enzyme
  can affect its activity
• Temperature
• pH