Chapter 2: Chemistry of Life Part B: Organic Chemistry

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Chapter 2 Chemistry of LifePart B Organic
Chemistry
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CARBON

• Organic chemistry is the study of compounds that
  contain bonds between carbon atoms.
• Life is based on the unique chemical and physical
  properties of carbon.
• It only makes up about 0.025 percent of the
  Earth's crust.
• Carbon reacts with more types atoms and forms
  more compounds than all the other elements put
  together.

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CARBON COMPOUNDS

• A carbon atom
• has four electrons in its outermost energy level.
• readily forms four covalent bonds with other
  atoms.
• unlike other atoms, carbon readily bonds with
  itself (other carbon atoms) to form straight
  chains, branched chains or rings.

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Carbon Bonding

• A covalent bond formed when two atoms share one
  pair of electrons is called a single bond.
• Carbon can also share two or even three pairs of
  electrons with another atom double and triple
  bonds.

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Functional Groups

• Clusters of atoms, called functional groups,
  influence the properties of the molecules they
  compose.
• Functional groups important to biology
• -OH hydroxyl group
• -COOH carboxyl group
• -NH3 amino group
• -PO4 phosphate group

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Major Classes

• There are four major classes of organic compounds
  found in living things
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

Insect chitin a structural polysaccharide
Spider silk a structural protein
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Large Carbon Molecules

• In many carbon compounds, the molecules are built
  up from smaller, simpler molecules known as
  monomers.
• Monomers can bond with one another to form
  complex molecules known as polymers.
• Large polymers are called macromolecules.

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Making Macromolecules

• Monomers link to form polymers through
  condensation reactions (dehydration synthesis).

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Breaking Macromolecules

• Hydrolysis, the addition of water to complex
  molecules, can break the bonds that hold them.

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Carbohydrates

• Composition
• only carbon, hydrogen and oxygen - in the ratio
  121 (CH2O)n ex. C6H12O6
• Function
• store energy and provide structural support.
• Types
• carbohydrates exist as monosacchrides,
  disaccharides or polysaccharides.
• Examples
• Glucose, starch, cellulose

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Examples

• Monosaccharides
• Glucose
  Fructose
• Disaccharides
• Sucrose

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Starch and Cellulose(polysaccharides)

• Glucose molecules in cellulose (above, right) are
  linked in ? bonds which we cannot digest

• Glucose molecules in starch (below, right) are
  linked in ? bonds which we can break down.

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Lipids

• Properties
• Nonpolar molecules not soluble or mostly
  insoluble in water
• Function
• Store energy and are a component of cell
  membranes (2x as much energy as CHO or proteins)
• Types
• Some are saturated (single bonds only - full of
  hydrogens) others are unsaturated (some double
  or triple bonds).
• Examples
• oil, fats, waxes, phospholipids, cholesterol
  (steroids), and even the pigment chlorophyll.

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Saturated vs. unsaturated fats

• Liquid oils, mostly from plants, contain
  unsaturated fatty acidswith carbon-carbon double
  bonds
• Fats, from animals, contain mostly saturated
  fatty acids

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A special class of lipids - Phospholipids

• Phospholipids two fatty acids and a phosphate
  joined to a glycerol (important in biological
  membranes)
• Phospholipids consist of two parts
• polar (hydrophilic) heads
• nonpolar (hydrophobic) tails

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Phospholipids
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Proteins

• Composition
• Composed of C, H, O and nitrogen.
• Monomer amino acids
• -about 20 kinds used in cells
• -contain amino group
• -contain single H
• -contain carboxyl group
• -contain R group the group that varies

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Proteins
Peptide bonds

• Proteins play an important role in structure and
  metabolic processes.
• The sequence of amino acids in a protein
  determines its shape, chemical properties and
  function.
• Two amino acids join to form a covalent bond,
  called a peptide bond.
• A very long chain is called a polypeptide.
• Examples hair, muscles, feathers, collagen, egg
  whites.

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Proteins

• Four levels of structure of proteins -
  polypeptide

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Proteins

• Proteins are the basic molecules that form
• Enzymes (discussed later in chapter)
• Hair
• Muscles
• Hemoglobin in blood
• Collagen in skin, ligaments, tendons, and bones
• Antibodies that help fight infection

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Nucleic acids

• Nucleic acid is a long chain of monomers called
  nucleotides.
• Nucleotides are made of three separate functional
  parts a sugar, a base, and a phosphate group.
• DNA or deoxyribonucleic acid, store hereditary
  information in the chromosomes in the form of
  long spiraling strands of polynucleotides

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DNA and RNA

• DNA exists as twin strands arranged in a double
  helix.
• RNA usually exists as single strands of
  nucleotides.
• Types of RNA function as enzymes, others play key
  roles in protein synthesis.

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Energy and Chemical Reactions

• Energy is the ability to move or change matter.
• Energy can be converted from one form to another
  (e.g. from potential to kinetic energy)
• But the total amount of energy does not change
• Energy can be stored or released by chemical
  reactions.

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ATP

• ATP or Adenosine triphosphate is a nucleotide
  that carries energy in extra phosphate groups.
• ATP supplies the energy that fuels cellular
  functions.
• It is the only form of energy usable by living
  cells

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Chemical Reactions

• A chemical reaction is a process where bonds
  between atoms are broken and new bonds formed
  producing different substances.
• Starting materials are called reactants and newly
  formed materials are called products.
• REACTANTS ?PRODUCTS

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Types of Reactions

• In a chemical reaction, energy is absorbed or
  released when chemical bonds are broken and new
  ones are formed.
• Metabolism is the term used to describe all of
  the chemical reactions
• that occur within an
• organism.

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Activation Energy

• The energy needed to start a chemical reaction is
  called activation energy.
• It is like giving a boulder a push to start it
  rolling downhill.
• Enzymes are catalyststhey lower the activation
  energy required for a chemical reaction to occur
  and this speeds up the reaction.

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Enzymes

• Most enzymes are proteins
• Without enzymes chemical reactions would not
  occur fast enough to sustain life.

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Enzyme Specificity

• Enzyme reactions depend upon a physical fit
  between enzyme molecule and its substrate, the
  reactant being catalyzed.
• Substrates attach to the enzyme at a place known
  as the active site.

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Enzyme Function

• When a substrate attaches to an enzymes active
  site, the enzymes shape changes slightly
• At the active site, enzyme and substrate interact
  in a way that reduces the activation energy.
• When the reaction is complete, the products are
  released from the enzyme.
• Enzymes work because they maintain a specific
  shape.

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Factors Affecting Enzyme Activity

• Cold temperatures slow down molecular motion and
  slow reactions reversibly.
• High heat cause vibrations that can disrupt
  delicate bonds that hold enzyme shape usually
  not reversible
• Optimum temperature for human enzymes 37?C
• Each enzyme functions best over a certain pH
  range.