The Molecular Building Blocks of Life

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The Molecular Building Blocks of Life

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Objectives

• 3.2.1 Distinguish between organic and inorganic
  compounds.
• 3.2.2 Recognize the physical differences
  between the macromolecules that are the
  building blocks of life.
• 3.2.3 State the uses for carbohydrates, lipids,
  nucleic acids, and proteins

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The Importance of carbon

• Cells are 70-95 water, the remainder is mostly
  carbon-based compounds.
• Proteins, DNA, carbohydrates, lipids
  distinguish living matter from inorganic
  material all are composed of carbon atoms
  bonded to each other to atoms of other
  elements, including H, O, N, S, P (percentages
  are quite uniform in all life).
• oxygen (65 percent)
• carbon (18 percent)
• hydrogen (10 percent)
• nitrogen (3 percent)
• phosphorus (1 percent) and
• sulfur (0.2 percent).

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Organic chemistry

• Organic chemistry is the study of carbon
  compounds.
• Produced not only in biological processes, they
  can also be synthesized by non-living reactions.
• Organic compounds range from simple CH4
  (below), to complex molecules, like proteins
  DNA (at right).

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Organic chemistry

• Organic compounds contain carbon hydrogen
  together!
• CH4 methane, C8H18 octane, C6H12O6 glucose
• If a carbon compound is not accompanied by
  hydrogen, it is considered inorganic.
• CO2 inorganic (no H)
• CCl4 inorganic (no H)
• CoCl2 inorganic (no C)
• CaHPO4 inorganic (no C)
• HCl inorganic (no C)
• Dont be fooled!

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Atomic carbon

• Carbon atoms are the most versatile building
  blocks of molecules.
• With a total of 6 e-, a C atom has 2 in the first
  shell and 4 in the second shell.
• Only outer shell elec- trons are involved in
  chemical reactions, so C has 4 e- to
  share (it makes 4 attachments).

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Carbon is tetravalent

• Carbon shares 4 electrons.

Note C makes 4 attachments, but H makes only 1.
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Carbon is tetravalent

• Carbon can bond with itself there are still
  always 4 attachments (4 bonds).
• Ethylene (-ene signifies a double bond)
• Isomers of butyne
• (-yne signifies a triple bond) still
  a total of four bonds on each
  carbon atom.

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Carbon is tetravalent

• The e- configuration of C lets it form covalent
  bonds with many different elements.
• In carbon dioxide, one C atom forms 2 double
  bonds with 2 different O atoms. The structural
  formula, O C O, shows that each atom has
  completed its valence shells. CO2 is the source
  for all organic molecules in organisms via the
  process of photosynthesis.

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Carbon is tetravalent

• Another example
• Urea, CO(NH2)2, is a simple organic
  molecule in which each atom has enough
  covalent bonds to
  complete its valence shell.
• H needs 1 e-
• O needs 2 e-
• N needs 3 e-

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Hydrocarbons

• Hydrocarbons organic molecules that consist of
  only C H.
• Hydrocarbons are the major component of
  petroleum.
• Petroleum is a fossil fuel because it consists of
  the partially decomposed remains of organisms
  that lived millions of years ago.

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Carbon-based life forms

• Life on Earth is based on carbon.
• Four types of carbon molecules are building
  blocks.
• Carbohydrates
• Lipids
• Nucleic acids
• Proteins

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Carbohydrates

• Function fuel and building material made of
  equal amounts of CH2O (carbon hydrates). H 2x
  O.
• Monosaccharides (simple sugars).
• Ex glucose
• Disaccharides (double sugars).
• Ex sucrose
• Polysaccharides are long chains of
  monosaccharides.
• Ex starch (in flour)

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Carbohydrates

• Monosaccharides have molecular formulas that are
  some multiple of CH2O. Ex glucose - C6H12O6.
  (H 2x O)
• Most names for sugars end in ose glucose,
  ribose.
• Disaccharides form from monosaccharides by
  dehydration (an H and an OH are removed).

Glucose glucose produces maltose (and water)
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Carbohydrates

• Polysaccharides are polymers of hundreds to
  thousands of monosaccharides.
• Function in energy storage (used as needed).
• Ex starch (plants) glycogen (in animals
  livers)
• Function as strong building materials. Ex
  cellulose

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Lipids

• Lipids are hydrophobic dont mix with water.
• In a triglyceride, three fatty acids (same or
  different) are joined to glycerol. Made of C, H,
  O, but the HO ratio is much greater than 21.

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Lipids

• A saturated fat has no carbon-carbon double
  bonds, and it is straight.
  They pack together solid at room temperature.
• Unsaturated fats have one or more carbon-carbon
  double bonds, and they bend. They cant get
  close to each other, so they are liquid at room
  temperature.

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Lipids

• Saturated fats come from animal products.
• Ex butter, lard
• A diet rich in saturated fats may contribute to
  cardiovascular disease (heart attack, stroke)
  through plaque deposits in arteries obesity,
  diabetes.

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Lipids

• Unsaturated fats come from plant fish products.
• Ex olive oil, corn oil, safflower oil, fish
  oils.
• Generally considered healthier for the heart.

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Lipids

• Functions of lipids
• Nutrition 1g of fat contains twice as much
  energy as 1g of carbohydrate.
• Protection cushions vital organs insulates
  them.
• This subcutaneous layer is
  especially thick in whales,
  seals, and most other
  marine mammals.

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Lipids

• Functions of lipids
• Phospholipids major components of cell
  membranes.
• Have two fatty acids attached to glycerol and a
  phosphate group at the third position.

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Lipids

• Functions of lipids
• Waxes reduce water loss by plants.
• Carnauba wax
• Steroids
• Cholesterol is a component in animal cell
  membrane.
• Many steroids are hormones.

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Nucleic acids

• All molecules of the body are programmed by a
  genetic code in the organisms DNA, a polymer of
  nucleic acids.
• Nucleic acids store and transmit hereditary
  in- formation.
• Made of C, H, O, N, P.

A nucleic acid
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Nucleic acids

• There are two types of nucleic acid polymers
• Ribonucleic acid (RNA)
• Single-stranded.
• Contains adenine, guanine,
  cytosine, and uracil.
• Sugar is ribose.
• Deoxyribonucleic acid (DNA)
• Double stranded.
• Contains adenine, guanine, cytosine, and thymine.
• Sugar is deoxyribose.

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Proteins

• Humans have at least 30,000 different proteins,
  each with a unique structure and function.
• Functions include structural support, storage,
  transport of materials, intercellular signaling,
  movement, and defense.
• Enzymes are one class of proteins that regulate
  metabolism by moderating chemical reactions.
• All proteins are 3 dimensional.
• All are constructed from the same set of 20
  monomers, called amino acids.
• All are made of C, H, O, and N (2 also contain S).

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Proteins

• Amino acids are joined by
  dehydration the resulting covalent
  bond is called a peptide
  bond.
• Polymers of amino acids are called
  polypeptides.

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Proteins

• A proteins function depends on
  its precise twisting, folding, and
  coiling into a unique
  shape.
• The order of amino acids determines what the
  three- dimensional shape will be.
• Folding of a protein occurs spontaneously an
  emergent property resulting from
  its specific molecular order.

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Proteins

• In individuals with sickle cell disease, abnormal
  hemoglobins develop because of a single amino
  acid substitution.

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Proteins

• Fibrous proteins are long, insoluble molecules .
• For movement (muscle fibers)
• For structure and support.  
• Collagen in skin.
• Cartilage connects tissues.
• Keratin is found
• in hair, horns, wool,
  nails, and feathers.

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Proteins

• Globular proteins are soluble and form compact
  spheroidal molecules in water.  
• Antibodies for immunity.
• Enzymes are involved in chemical reactions
  - metabolism (enzymes generally end in
  ase).
• Transport proteins and receptor proteins in
  the cell membrane.

Hemoglobin transport of oxygen
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Proteins

• Transport proteins and receptor proteins in the
  cell membrane capture chemicals in the blood and
  may move them into the cell.

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Proteins

• Enzymes catalyze chemical reactions (metabolism).
• One enzyme is specific for each chemical
  reaction.
• Enzymes convert one substrate (the
  raw material) into some product.
• Ex sucrase binds to sucrose and
  breaks this disac-
  charide into fruc-
  tose and glucose.
• Enzymes end in ase.

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Proteins

• A proteins shape can change in response to
  changes in pH, salt concentration, temperature.
  These forces disrupt the bonds that maintain the
  proteins shape. This is called denaturation.
  Then the protein wont work right!