MCB 2000 Lecture Notes - Lecture 3: Disulfide, Alpha Helix, Membrane Lipids
23 May 2018
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Lecture 3
• Polymers
o Carbohydrates
▪ Nutrients
• Agar = important component of culture media
▪ Structural support/protection
• Chitin = cell wall of fungi
• Peptidoglycan = component of bacterial cell wall
• Lipopolysaccharides = component of gram-neg cell wall
• Cellulose = cell wall of plants
o Made of glucose molecules
o Most abundant compound on earth
o Can only be broken down by bacteria
▪ Receptors
• Glycocalyx = attachment or as site for receptors, covers exterior of
cell
o Lipids
▪ Steroids
• Cell membranes
• Animal hormones
• Cholesterol
▪ Waxes
• Natural waterproofing compounds
• TB has unique wax in their cell wall that contributes to their
pathogenicity
▪ Membrane lipids
• Hydrophilic region on the outsides of the membrane
• Hydrophobic region on the inside of the membrane
• Naturally assume double layers
o Proteins
▪ Most abundant molecule in cells
▪ Amino acids linked by peptide bonds
▪ Polypeptide = links of unspecified number of amino acids—smaller
subunit of a protein
▪ Structure
• Primary = AAs in a linear chain (polypeptide) bonded together by
peptide bonds
• Secondary = polypeptide folds and is reinforced by H bonds
o Alpha helix
o Beta pleated sheet
• Tertiary = created by more folding and addition bonds (disulfide
bridges) between different parts
o Most proteins become functional once they reach tertiary
structure
• Quaternary = formed when more than one polypeptide forms a
large, multiunit protein
o Ex: hemoglobin is 4 polypeptides together
▪ Bonding and folding
• Each protein has unique shape with distinct surface patterm
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