PROTEINS The most complex and multifunctional class of organic
molecules Most genes are instructions for making protein molecules
Large molecules with complex 3-dimensional shapes Polymers of amino
acids
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Protein functions Catalytic enzymes control reactions
Structural e.g. collagen, keratin, silk Storage of amino acids for
growth Transport e.g. O 2 and hemoglobin Hormones communication
among cells Receptors receiving chemical signals Contractile e.g.
actin and myosin Defensive e.g. antibodies
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CC O O-H H2N H2N R Amino Carboxyl Functional group varies-
>20 kinds Ionized form Amino acid structure O-O- CC O +H3N +H3N
R H H
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O-O- CC O +H3N +H3N H asymmetric -carbon enantiomers Only
L-forms are made and used by organisms
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The 20 amino acids of proteins: nonpolar, hydrophobic side
chains
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The 20 amino acids of proteins: polar and electrically charged
side chains
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Proteins have complex, 3-D shapes Alternative diagrams of the
protein lysozyme
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the amino acid sequence of a protein Determined by the genetic
information that directs protein synthesis Primary structure
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A single amino acid substitution in a protein causes sickle-
cell disease
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Secondary structure repetitive folding due to H-bonds between
amino and carbonyl -helix and -sheet
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Tertiary Structure -non-repeating folding
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Quaternary structure- multimeric proteins
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Review: the four levels of protein structure
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Disruption of 2, 3, or 4 structure by heat, pH, or ions =
cooking Denaturation
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NUCLEIC ACIDS (DNA, RNA) =polynucleotides polymers of
nucleotides Nucleotide structure: phosphate Nitrogenous base
pentose N N
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Nucleotide function nucleoside triphosphates- (ATP, GTP) are
energy carriers Monomers for building polynucleotides
Polynucleotide function DNA, RNA are information carriers Some RNAs
are catalysts More about nucleic acids later, when we consider
molecular genetics
