BCH 261 Lecture Notes - Lecture 7: Lactose Permease, Enolase, Zwitterion
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30 Nov 2020
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Lecture 7
● Proteins Functions
○ • Catalysis:
■ enolase (in the glycolytic pathway)
■ DNA polymerase (in DNA replication)
○ • Transport:
■ hemoglobin (transports O2 in the blood)
■ lactose permease (transports lactose across the cell membrane)
○ • Structure:
■ collagen (connective tissue)
■ keratin (hair, nails, feathers, horns)
○ • Motion:
■ myosin (muscle tissue)
■ actin (muscle tissue, cell motility)
○ Human genome encodes > 20,000 proteins
● Proteins = polymers of amino acids
○ Proteins are heteropolymers of 20 common amino acids
○ Amino acids have properties that are well suited to carry out a variety of
biological functions: Capacity to polymerize; Useful acid-base properties;
Varied physical properties; Varied chemical functionality
● Amino acid structure
○ A nonionized amino acid showing the carboxylic acid group, the α-amino
group, the hydrogen bonded to the α -carbon, and the side chain (R
group) that gives the amino acid its unique properties
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○ Zwitterion: amino acid at neutral charge, where the α-carboxylic acid
group is deprotonated and the α-amino group is protonated. The negative
charge on the α-carboxylate is delocalized over the two oxygen atoms
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○ Classification of 20 amino acids
■ Non-polar, aliphatic
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■ Non-polar, aromatic
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■ Polar, uncharged
■ Basic
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■ Acidic