Lipids, proteins, and nucleic acids

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Lipids, proteins, and nucleic acids

• Biological molecules, continued

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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

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Triglycerides

• Glycerol covalently linked to three fatty acids
• Fatty acids may be saturated or unsaturated
• Affects the melting point of the triglyceride

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Saturated and unsaturated lipids
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Other types of lipids phospholipids
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Steroids

• Four fused rings with functional groups
• Found in cell membranes of animal cells
• Cholesterol is a precursor for several hormones

cholesterol
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Prostaglandins

• Formed from fatty acids
• Are derived from membrane phospholipids
• Help regulate responses to stimuli

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Functions of proteins
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continued
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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

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Amino acids are joined by peptide bonds
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Categories of amino acids
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Levels of protein structure primary

• Length and order of amino acids in the chain is
  genetically determined
• Basis for all further levels of protein structure

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Levels of protein structure secondary

• Regions of amino acid chain may be coiled or
  flattened
• Achieved through hydrogen bonding

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Tertiary structure

• Interactions between R groups
• Remember protein has three-dimensional structure
• In cells, proteins are formed in an aqueous
  environment

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Quaternary structure

• Some proteins are formed with more than one chain

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Protein structure is determined genetically
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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

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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

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Protein sequence information is contained in DNA

• DNA contains the genetic information
• DNA can replicate itself
• RNA is required for actual protein synthesis

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Nucleic acids are made of nucleotides held
together by a sugar-phosphate backbone
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DNA vs. RNA

• Thymine vs. uracil
• Double-stranded vs. single stranded
• Deoxyribose vs. ribose
• Stability
• Function

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Structures of DNA and tRNA
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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

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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