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Lipids_ proteins_ and nucleic acids

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					Lipids, proteins, and nucleic acids

      Biologic molecules, continued
         Lipids are hydrophobic
• Lots of nonpolar bonds (C-H)
• Tend to cluster in water
• If the molecule has polar (hydrophilic) regions,
  they are exposed on the surface
                  Triglycerides
• Glycerol covalently
  linked to three fatty
  acids
• Fatty acids may be
  saturated or
  unsaturated
• Affects the melting
  point of the triglyceride
           Other types of lipids
• Terpenes are found in
  pigments
• Steroids are found in
  cell membranes
               Prostaglandins
• Formed from fatty acids
• Are derived from
  membrane
  phospholipids
• Help regulate responses
  to stimuli
      Phospholipid structure and cell
              membranes
• Amphipathic moelcule
  (polar head, nonpolar
  tails)
• Phospholipids
  spontaneously form
  micelles or lipid bilayers
Functions of proteins
   Why are proteins so versatile?
• Twenty different amino acids (with a few
  variants)
• Amino acids have many different properties
• Proteins vary in number, sequence of amino
  acids
• This affects the structure and function of the
  protein
Amino acids are joined by peptide
             bonds
Categories of amino acids
R groups of amino acids can react with
             each other
Levels of protein structure
    Protein structure is determined
               genetically
• Elaborate cellular mechanism involved in
  forming proteins
• What happens of the amino acid sequence is
  altered?
              Motifs and domains
• Protein structure is
  extremely complex
• Studying protein
  structure is complex, too
   – X-ray crystallography
   – NMR
   – Modeling
• Proteins with similar
  activities have some
  common features
Proteins are “helped” to fold correctly
• Chaperone proteins are
  found throughout
  nature
• Misfolded proteins are
  usually degraded
• Changes in the
  environment can also
  affect protein folding
     Protein sequence information is
            contained in DNA
• DNA contains the
  genetic information
• DNA can replicate itself
• RNA is required for
  actual protein synthesis
Nucleic acids are made of nucleotides
Nucleotides are joined together by a
    sugar-phosphate backbone
Double-stranded DNA
                 DNA vs. RNA
•   Thymine vs. uracil
•   Double-stranded vs. single stranded
•   Deoxyribose vs. ribose
•   Stability
•   Function
           ATP contains adenine
• High-energy bonds are
  formed and broken
• Energy from ATP is used
  to drive energy-
  requiring reactions
• Energy from ATP
  hydrolysis is used to do
  cellular work
                 Summary
• Molecules are made of atoms, and acquire
  new properties based on their structure
• Molecular structure and function are affected
  by their “behavior” in water
• Carbohydrates, lipids, proteins and nucleic
  acids all contain C, H, and O- but have unique
  functions in cells

				
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posted:5/25/2013
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