Topic Carbohydrates Lipids and Proteins

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Topic Carbohydrates Lipids and Proteins Powered By Docstoc
					Topic 2.2 Macromolecules
  Carbohydrates, Lipids,
Proteins and Nucleic Acids
     Subtopics: 2.2.1-2.2.10
   Describe the chemical composition and general structure of carbohydrates.
   Describe three classes of carbohydrates, how they are synthesized, specific
    examples of each (name, empirical and structural formulas) and their functions.
   Define and describe examples of monosaccharide isomers
   Describe the chemical composition and structures of lipids
   Describe the formation of a triglyceride
   Compare and contrast saturated and unsaturated triglycerides
   List and describe examples of various forms of lipids and their functions in
    living things.
   Describe the chemical composition of proteins
   Describe the general structure of an amino acid and the variation of amino
    acids (how many, how are they similar, how they are different)
   Describe the formation of peptide bonds and how polypeptide chains are
   Describe the 4 levels of protein structure.
   Describe the major functions of proteins.
   Describe the function, structure, and formation of nucleic acids.
  All carbohydrates are composed of carbon,
  hydrogen, and oxygen in a 1:2:1 empirical ratio.
 The general empirical formula for a
  carbohydrate is CH2O.
     If a carbohydrate has 5 carbons atoms, what
  would be its empirical formula? C5H10O5
     If a carbohydrate has 12 hydrogen atoms
  present, what would be its empirical formula?
 Most carbohydrates end with the suffix -ose
     Functions of Carbohydrates
    Provide energy source: A fuel source when catabolized
    during cellular respiration. Energy is stored in the
    chemical bonds within the molecule and released during
    cellular respiration. Usually simple sugars.
   Provide energy storage: Plants store energy in a
    complex carbohydrate form called starch (amylose).
    Animals store energy in a complex carbohydrate in their
    muscle tissue and liver in the called glycogen.
   Structural Building Material: Plants build their cell walls
    of a complex carbohydrate material called cellulose.
    Animals such as arthropods build their exoskeletons of a
    complex carbohydrate called chitin. Chitin is also found
    in the cell walls of Fungi.
       Classes of Carbohydrates
   There are three major classes of carbohydrates:
         1. Monosaccharides (simple sugars) These are
    the monomers or building blocks for all other classes of
    carbohydrates. Examples: glucose, fructose, galactose,
    and ribose.
         2. Disaccharides are produced by joining two
    simple sugars by dehydration synthesis forming a
    covalent bond between them. Examples: sucrose (table
    sugar), maltose, lactose
         3. Polysaccharides (complex carbohydrates) are
    produced by joining many monosaccharides together by
    many dehydration synthesis reactions forming a polymer
    molecule. Examples: amylose, glycogen, cellulose, and
Monosaccharides (Simple sugars)
   They may exist in a linear molecule or in ring forms.
   They are classified according to the number of carbon
    atoms in their molecule.
    5 carbons are called pentoses ex. Ribose
    6 carbons are called hexoses ex. Glucose
   Many forms exists as isomers. Isomers are molecules
    which have the same empirical formula (recipe) but have
    different structures (shapes) due to arrangement of the
    atoms in the molecule. This also gives them different
    properties. Glucose and fructose both have the
    empirical formula C6H12O6, but they have different
    structural formulas or shapes.
Monosaccharide Structure

                 The diagram to the left
                 shows two hexoses that
                 are isomers. The one
                 furthest to the left is the
                 structural model of alpha
                 glucose and the closest
                 to the right is galactose.
                 If you count the numbers
                 of each atom type, you
                 will see they are the same.
    Monosaccharide Isomers
    H                               H
                                                     O             H
    C                  O
                                      C                            C
H   H                       H
C                           C
                                      OH   OH                 H
    OH                  H
                                           C                   C
OH C                    C   OH
    H                  OH                  H                  OH

         α- GLUCOSE                            FRUCTOSE          H
What is the empirical formula for these molecules?       C6H12O6
Disaccharide Formation and Structure
   Disaccharides are formed when two
    monosaccharides are joined by dehydration
    synthesis reaction.
      Disaccharide Formation and Structure

     CH2OH                     CH2OH                       CH2OH                   CH2OH

H            O   H        H            O   H          H            O   H       H           O   H

OH               OH       HO               OH         OH                                       OH

    α- GLUCOSE             α- GLUCOSE                              MALTOSE
Disaccharide Structure

Sucrose         Maltose
    Polysaccharide Structure and
 Polysaccharides are chains of
  monosaccharides that have been joined by
  many dehydration synthesis reactions.
 The function of the polysaccharide depends
  on what type of isomer of glucose the
  polysaccharide is made. This determines how
  the glucose molecules bond together (linkage)
  and whether they can be used for energy
  storage or structural molecules.
Alpha and Beta Glucose and Their
          1,4 Linkages
                   Alpha and beta glucose are
                   structural isomers. They differ
                   only in the location of the
                   hydrogen and hydroxl group
                   location on carbon 1.

                   Alpha linkage can be broken by
                   enzymes present in plants and
                   animals. In other words, it can
                   be metabolized. (energy storage)

                   Beta linkage can not be broken
                   by enzymes present in plants
                   and animal, therefore it can not
                   be metabolized. (structural)
     Storage Polysaccharides
Starch and glycogen both have alpha 1,4 linkage
  and form helical chains that are often highly

                               The diagram to the left
                               show starch or amylose
                               granules in a plastid of a
                               plant cell.

                               The diagram to the left
                               shows glycogen granules
                               in a liver section of an
                               animal. Glycogen is
                               usually more highly
                               branched than amylose.
      Structural Polysaccharides
   Cellulose is the plant structural carbohydrate and has
    beta 1,4 linkage. Cellulose is the primary component of
    the plants primary or outermost cell wall.
    Have You Had Your Fiber Today?
   Because cellulose has beta
    1,4 linkage all animals lack
    the enzymes necessary to
    digest this material. In our
    case it simply passes
    through our gut and out of
    the body. We call it fiber or
    roughage. Animals such as
    termites and cows rely on
    simple, symbiotic,
    unicellular organisms such
    as protozoa or bacteria to
    carryout the job of digestion
    for them! In return the tiny
    organisms live in an ideal
    environment with a bountiful
    food supply.
      Structural Polysaccharides
   Chitin is the “plastic-
    like” material that
    composes the
    exoskeletons of
    arthropods (insects,
    arachnids, and
    crustaceans). Most
    fungi (mushrooms)
    have chitin present
    within their cell walls.
                               Above is a structural monomer of
 Lipids  are complex molecules
  composed of carbon, hydrogen, and
 Most lipids are non-polar and are
  hydrophobic because they contain
  hydrocarbon chains.
 If there are double or triple bonds in the
  hydrocarbon chain the lipids are said to
  be ―unsaturated‖
            Lipid Functions
 Energy storage: Fats and oils.
 Waterproofing: Waxes and oils
 Insulation: Fat layers (blubber)
 Cushioning: Fat layers (soles of your feet)
 Regulating metabolic processes: Steroids
 Building component of cell membranes:
       Lipid structure (Triglyceride)
      A triglyceride is
      composed of an alcohol
      called glycerol
      covalently bonded to
      three fatty acid
      molecules by
      dehydration synthesis
      reactions. This process
      forms three ester groups
      between the alcohol and
      one with each fatty acid
      chain.                               Is this a saturated or unsaturated
                                           Fat? Why or Why not?
It is saturated because there are no double bonds between carbon atoms in the
fatty acid hydrocarbon chains.
      Triglyceride formation

  H                                H20         H
               O HHHHH                           O HHHHH
 H-C—OH      HO-C-C-C-C-C-C-H              H-C—O-C-C-C-C-C-C-H
                  HHHHH                             HHHHH
                O HHHHH            H20            O HHHHH
 H-C—OH      HO-C-C-C-C-C-C-H              H-C—O -C-C-C-C-C-C-H
                  HHHHH                             HHHHH
                O HHHHH            H20            O HHHHH
 H-C—OH      HO-C-C-C-C-C-C-H              H-C—O -C-C-C-C-C-C-H
                  HHHHH                             HHHHH
  H                                          H

GLYCEROL         FATTY ACIDS       3 H20           TRIGLYCERIDE

 What type of reaction forms a triglyceride?   Dehydration Synthesis
 Saturated vs. Unsaturated Fats
When double bonds form in hydrocarbon chains it causes
 them to bend. In unsaturated fats this prevents the
 molecules from being able to “stack” or “pack” themselves
 tightly, thus they remain in a liquid state at room
 temperature such as oils. If the hydrocarbon chains are
 saturated, the chains are straight and pack themselves
 close together forming a solid at room temperature
 (animal fat, butter, tallow, lard).
   Steroids are cyclic            Cholesterol
    hydrocarbons usually
    composed of four rings.
   They are involved with
    regulating metabolic
    processes in the body
    because many forms of them
    are hormones.
   Testosterone, estrogen, and
    progesterone are all
    examples of steroid
   Cholesterol is the most
    common steroid! It is the
    building block for other
    steroid hormones and also
    functions in cell membrane
Phospholipids are a special class of lipids
 composed of a phosphate group, glycerol
molecule, and two fatty acid chains. The
 phosphate region of the molecule is polar
 because it is negativley charged. This makes
 it attracted to water or hydrophilic because
 of waters bipolar nature. The fatty acid chain
 region is composed of hydrocarbon chains
 which are very non-polar, therefore this end
 is hydrophobic or repels water.
Phospholipid Structure
        Phospholipid Behavior
Because of their bipolar
  nature,when placed in
  water phospholipids
  orient themselves in
  small spheres or
  ―bubbles‖ with their
  nonpolar (hydrophobic)
  regions oriented away
  from water and their
  polar (hydrophilic)
  regions exposed to
  water. These structure
  are called micelles and
  are similar in structure
  the cell membrane
  which is composed in
  part of a phospholipid
 Proteins  are composed primarily of
  carbon, hydrogen, nitrogen,and oxygen.
  However, some contain sulfur.
 They are all composed of structural
  monomers called amino acids.
 Their differences from organism to
  organism is due to differences in the DNA
  which contains the instructions for their
  formation. Ex. Eye color, Blood type
               Protein Functions
   Structure: Building structural components of organisms
    (collagen, elastin, keratin, microtubules, microfilaments)
   Regulation of metabolic processes: Hormones (insulin)
 Carrying       out of metabolic processes:
   Membrane component: Carrier proteins, Protein pumps,
    Transport of materials through membrane phospholipid
   Self and non-self recognition: Major histocompatibility
    complexes (Tissue rejection, immune responses).
   Membrane receptors: Hormone receptors and
    neurotransmitter receptors.
Amino Acids: Structural Monomers
Amino acids derive their name
  due to the presence of an
  amine group and a
  carboxylic group as part of
  their composition. They
  have a central carbon with
  the amine group, a carboxyl
  group, a hydrogen, and a
  variable group (R group)
  attached to it. The variable
  group is what is different
  from amino acid to amino
  acid and it is what give the
  amino acid its identity.
  There are twenty different
  variable groups, therefore
  there are twenty different
  amino acids.
Amino Acid Variety
     Peptide Bond, Dipeptide, and
        Polypeptide Formation
A peptide bond is the bond
  that is created when two
  amino acids are
  covalently bonded
  together. The carboxyl
  group of the first is
  bonded to the amine
  group of the second.
  This is carried out by a
  dehydration synthesis
  reaction with the loss of a
  water molecule. This
  forms a dipeptide.
      Peptide Bond, Dipeptide, and
         Polypeptide Formation
                 H       H    O         H         H    O

                     N   C    C –OH + N           C    C –OH

                 H       R1             H         R2


The peptide bond                                             This is called a
                        H     H     O             H    O
is created between                                           dipeptide. If the
the carboxyl carbon                                          process is
                          N   C     C– N          C    C –OH
of the first amino acid                                      repeated many
and the amine group H                                        times a
                              R1            H     R2
of the second amino                                          polypeptide is
acid.                             Peptide Bond               formed.
    Levels of Protein Structure
Proteins are very complex molecules and their
   shape or structure determines their function.
   Most proteins have 4 levels of structure. They
   a. Primary Level
   b. Secondary Level
   c. Tertiary Level
   d. Quaternary Level
If any level of structure is changed it can create
   faulty or nonfunctioning proteins!
    Levels of Protein Structure
The Primary Level is
  determined by the
  number of amino
  acids, the type of
  amino acids, and
  the sequence of the
  amino acids in the
  polypeptide chain.
       Levels of Protein Structure
The Secondary Level is
  due to interactions
  between amino acids in
  the chain, usually due
  to hydrogen bonding
  between oxygen and
  hydrogen atoms in
  different amino acids.
  Two general forms are
  taken. Alpha helix, a
  spiral structure,
  common in globular
  proteins, or a Beta
  pleated sheet structure,
  common in structural
     Levels of Protein Structure
The Tertiary Level is due to
  the “folding over” of the
  alpha helical or beta
  pleated sheet structure
  on itself. This
  configuration is due again
  to hydrogen bonding,
  interactions, ionic
  bonding interactions,
  and the interaction of
  sulfur groups on the
  variable groups of some
  amino acids forming
  weak interactions called
  disulfide bridges.
    Levels of Protein Structure
The Quaternary Level
  of structure is due to
  the interactions of
  more than one
  polypeptide chain to
  form the complete,
  functional protein.
  Hemoglobin and
  antibodies exhibit this
  level of structure.
Levels of Protein Structure
  Example of Modification in Levels
       of Protein Structure
Sickle-cell anemia is
   due to a change in
   protein structure at
   the primary level.
   Once the change is
   made at the primary
   level it has an effect
   on all subsequent
   levels. Resulting the
   formation or irregular
   hemoglobin protein
   that cause the
   molecule to take on
   an irregular form
   which in turns affects
   its normal function
   and the shape of the
   erythrocytes (red
   blood cells).
             Nucleic Acids
 Composed     of carbon, hydrogen, oxygen,
  nitrogen, and phosphorus
 Carriers of the genetic code (recipe book
  for proteins)
 Two types: DNA (deoxyribonucleic acid)
  and RNA (ribonucleic acid)
 Molecule responsible for heredity
       Nucleotide Monomers
Nucleic acids are composed of many monomers
 linked together by dehydration synthesis. These
 monomers are called nucleotides
 (nucleosides). These monomers are
 composed of a monosaccharide
 (deoxyribose in DNA or ribose RNA), a
 phosphate group, and a nitrogenous base.
 The nitrogenous bases found in DNA are
 adenine A, Thymine T, Guanine G, and
 Cytosine C. The nitrogenous bases found in
 RNA are Adenine A, Guanine G, Cytosine C,
 and Uracil U, which replaces thymine.
Nucleotide Structure
                   DNA Structure
The structure of DNA was
  discovered by an American
  scientist (James Watson) and
  a British scientist (Francis
  Crick) based on the work of
  Rosalind Franklin and Maurice
  Wilkins. In 1962 Watson and
  Crick received the Nobel Prize
  for their work. Wilkin later
  received a Nobel Prize for
  work relating to his
  contribution. Rosalind Franklin
  however, never received a
  Nobel Prize because she died
  of cancer before she was
  publicly recognized for her
  contributions to this effort.
The Double Alpha Helix of DNA
DNA is a double stranded,    5’
  alpha helical molecule.
  Each strand is composed
  of nucleotide covalently
  bonded between their
  phosphate groups and
  the deoxyribose sugar
  components in a 5,3
  linkage between the
  sugars and phosphates.
  The nitrogenous bases
  point outward from the
  linear alternating sugar
  phosphate backbone.
The Double Alpha Helix of DNA
When two strands of DNA
 join to form the alpha
 helix, it is due to
 hydrogen bonding
 between the
 complimentary purine and
 pyrimidine bases on each
 complimentary strand.
 Adenine forms hydrogen
 bonds with Thymine and
 Guanine forms hydrogen
 bonds with Cytosine.
 This is called
 Complimentary Base
The Double Alpha Helix of DNA
The complimentary
  strands run in
  opposite directions or
  anti-parallel to each
The Double Alpha Helix of DNA
The strands begin to spiral and due to hydrogen
  bonding takes on the double alpha helix form.
    Comparing and Contrasting DNA
              and RNA
 DNA bases (A,T,G,C)           RNA bases (A,U,G,C)
 Deoxyribose sugar             Ribose sugar
 Original information for      Working copy for making
  making proteins                proteins
 One form or type              Variety of forms, m-RNA,
 Found primarily in the         t-RNA, r-RNA
  nucleus forms                 Found in nucleus and
  chromosomes during cell        through the cell
  division                      Smaller molecules (single
 Large molecule (double         stranded)

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