Macromolecules

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Macromolecules

• The building blocks of life

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Macromolecules

• Cells are composed of several types of biological
  macromolecules.
• These function as energy-storage molecules,
  structural components, and in information
  storage, and are primarily composed of carbon,
  hydrogen and oxygen.

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Carbohydrates

• carbon, hydrogen oxygen in a 121 ratio
• exist as monosaccharides, disaccharides and
  polysaccharides
• among the most abundant molecules on Earth

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Monosaccharides

• single sugars
• general formula is (CH2O)n
• glucose (top) and ribose (bottom) are
  monosaccharides

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Disaccharides

• double sugars
• formed by dehydration synthesis from two
  monosaccharides
• sucrose, maltose, and lactose are all
  disaccharides

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Synthesis of Maltose
?- glucose
?-glucose
maltose
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Polysaccharides

• straight or branched chains of monosaccharides
  connected by glycosidic linkages
• storage (e.g. starch, glycogen) or structural
  (e.g. cellulose, chitin)

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Polysaccharide Structure
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Proteins

• proteins are chains of amino acids connected by
  peptide linkages
• order of amino acids for a particular protein is
  determined by the gene which codes for it

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Amino Acid Structure

• all amino acids have the same basic structure
• R group is different for each amino acid

amino group
carboxyl group
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Peptide Linkages
cysteine
glycine
peptide linkage
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Levels of Protein Structure

• Primary
• the specific sequence of amino acids
• coded by DNA

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• Secondary
• the folding or coiling of the amino acid chain
• caused by interactions between R groups
• ?-Helix
• ?-Pleated Sheet

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• Tertiary
• the unique three-dimensional shape of the protein
• enzymes are globular proteins
• collagen is a fibrous protein

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• Quaternary
• interactions between separate polypeptide chains,
  or subunits
• hemoglobin is composed of four subunits

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Lipids

• lipids are a group of hydrophobic molecules
• neutral fats are uncharged lipids composed of
  glycerol and fatty acids
• fats are solid at room temperature
• oils are liquid at room temperature
• steroids and phospholipids are amphiphilic

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Steroid Structure

• steroids all have the same basic structure of
  four fused hydrocarbon rings
• cholesterol is used to synthesize many other
  steroids in the body

cholesterol
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Phospholipid Structure

• glycerol backbone has two fatty acids and one
  charged inorganic phosphate group attached
• primary component of cell membranes

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Triglycerides

• triglycerides are neutral fats
• glycerol is the backbone molecule
• fatty acids attach to glycerol by ester linkages
• saturated fatty acids have no double bonds
  between carbons
• unsaturated fatty acids have at least one double
  bond between carbons

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Triglyceride Synthesis
glycerol
3 fatty acids
ester linkage
triglyceride
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Nucleic Acids

• Deoxyribonucleic Acid (DNA) and Ribonucleic Acid
  (RNA)
• composed of nitrogen-containing bases attached
  to a backbone of alternating pentose sugars and
  inorganic phosphate
• function in information storage (DNA) and
  transfer (RNA)

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Bases of DNA RNA
Purines Pyrimidines
adenine thymine
guanine cytosine
uracil
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DNA

• deoxyribose sugar
• adenine, guanine, cytosine, thymine bases
• arranged in a double helix

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RNA

• ribose sugar
• adenine, guanine, cytosine, uracil bases
• single-stranded

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References

• MIT Biology Hypertextbook(1996)
  http//esg-www.mit.edu8001/esgbio/lm/sugars/sugar
  s.html (3/9/2001)
• Farabee, M.J., (2001) An Online Biology Book.
  Chemistry 2 Water and Organic Molecules
  http//gened.emc.maricopa.edu/bio/bio181/BIOBK/Bio
  BookCHEM2.html (3/9/2002)
• A.C.D. Labs (2002) ChemSketch (Freeware),
  available for download at http//www.acdlabs.com/.
  Used for molecular structure diagrams.