The Chemical Building Blocks of Life

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The Chemical Building Blocks of Life

• Chapter 3

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Outline

• Biological Molecules
• Macromolecules
• Proteins
• Structure and Denaturation
• Nucleic Acids
• DNA and RNA
• Lipids
• Fats and Phospholipids
• Carbohydrates
• Transport and Storage

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Biological Molecules

• The framework of biological molecules consists of
  carbon bonded to other carbon molecules, or other
  types of atoms.
• Hydrocarbons consist of carbon and hydrogen.
• Covalent bonds store considerable energy.

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Biological Molecules

• Functional groups
• specific groups of atoms attached to carbon
  backbones
• retain definite chemical properties
• Macromolecules.
• proteins
• nucleic acids
• lipids
• carbohydrates

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Macromolecules

• Macromolecules are often polymers.
• long molecule built by linking together small,
  similar subunits
• Dehydration synthesis removes OH and H during
  synthesis of a new molecule.
• Hydrolysis breaks a covalent bond by adding OH
  and H.

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Proteins

• Protein functions
• enzyme catalysis
• defense
• transport
• support
• motion
• regulation
• storage

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Amino Acids

• contain an amino group (-NH2), a carboxyl group
  (-COOH) and a hydrogen atom, all bonded to a
  central carbon atom
• twenty common amino acids grouped into five
  classes based on side groups
• nonpolar amino acids
• polar uncharged amino acids
• charged amino acids
• aromatic amino acids
• special-function amino acids

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Amino Acids

• Peptide bond links two amino acids.
• A protein is composed of one or more long chains
  of amino acids linked by peptide bonds
  (polypeptides).

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Protein Structure

• Protein function is determined by its shape.
• Protein structure
• primary - specific amino acid sequence
• secondary - folding of amino acid chains
• motifs - folds or creases
• supersecondary structure

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Protein Structure

• tertiary - final folded shape of globular protein
• domains - functional units
• quaternary - forms when two or more polypeptide
  chains associate to form a functional protein

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Chaperone Proteins

• Chaperone proteins are special proteins which
  help new proteins fold correctly.
• Chaperone deficiencies may play a role in
  facilitating certain diseases.

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Unfolding Proteins

• Denaturation refers to the process of changing a
  proteins shape.
• usually rendered biologically inactive
• salt-curing and pickling used to preserve food

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Nucleic Acids

• Deoxyribonucleic Acid (DNA)
• Encodes information used to assemble proteins.
• Ribonucleic Acid (RNA)
• Reads DNA-encoded information to direct protein
  synthesis.

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Nucleic Acid Structure

• Nucleic acids are composed of long polymers of
  repeating subunits, nucleotides.
• five-carbon sugar
• phosphate
• nitrogenous base
• purines
• adenine and guanine
• pyrimidines
• cytosine, thymine, and uracil

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Nucleic Acid Structure

• DNA exists as double-stranded molecules.
• double helix
• complementary base pairing
• hydrogen bonding
• RNA exists as a single stand.
• contains ribose instead of deoxyribose
• contains uracil in place of thymine

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Structure of DNA
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Lipids

• Lipids are loosely defined as groups of molecules
  that are insoluble in water.
• fats and oils
• Phospholipids form the core of all biological
  membranes.
• composed of three subunits
• glycerol
• fatty acid
• phosphate group

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Fats and Other Lipids

• Fats consist a of glycerol molecule with three
  attached fatty acids (triglyceride /
  triglycerol).
• Saturated fats - all internal carbon atoms are
  bonded to at least two hydrogen atoms
• Unsaturated fats - at least one double bond
  between successive carbon atoms
• Polyunsaturated - contains more than one double
  bond
• usually liquid at room temperature

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Fats as Energy Storage Molecules

• Fats, on average, yield about 9 kcal per gram
  versus 4 kcal per gram for carbohydrates.
• Animal fats are saturated while most plant fats
  are unsaturated.
• Consumption of excess carbohydrates leads to
  conversion into starch, glycogen, or fats for
  future use.

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Carbohydrates

• Carbohydrates are loosely defined as molecules
  that contain carbon, hydrogen, and oxygen in a
  121 ratio.
• monosaccharides - simple sugars
• disaccharides - two monosaccharides joined by a
  covalent bond
• polysaccharides - macromolecules made of
  monosaccharide subunits
• isomers - alternative forms of the same substance

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Carbohydrate Transport and Storage

• Transport disaccharides
• Humans transport glucose as a simple
  monosaccharide.
• Plants transform glucose into a disaccharide
  transport form.
• Storage polysaccharides
• plant polysaccharides formed from glucose -
  starches
• most is amylopectin

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Structural Carbohydrates

• Cellulose - plants
• alpha form or beta form of ring
• Chitin - arthropods and fungi
• modified form of cellulose

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Summary

• Biological Molecules
• Macromolecules
• Proteins
• Structure and Denaturation
• Nucleic Acids
• DNA and RNA
• Lipids
• Fats and Phospholipids
• Carbohydrates
• Transport and Storage

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