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Two notable breakthroughs in the
history of biochemistry
(1) Discovery of the role of enzymes as
catalysts
(2) Identification of nucleic acids as
information molecules
Flow of information: from nucleic acids to proteins
DNA
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RNA
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Protein
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Functional groups in biochemistry
• Functional groups - specific parts of molecules
involved in biochemical reactions
• Figure 1.2 shows the general formulas of:
(a) Organic compounds
(b) Functional groups
(c) Linkages common in biochemistry
(R represents an alkyl group (CH3CH2)n-)
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Fig 1.2 (a) General formulas
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Fig 1.2(b) General Formulas
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Fig 1.2 (c) General Formulas
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1.3 Many Important Biomolecules
are Polymers
• Biopolymers - macromolecules created by
joining many smaller organic molecules
(monomers)
• Condensation reactions join monomers
(H2O is removed in the process)
• Residue - each monomer in a chain
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A. Proteins
• Proteins are composed of 20 common amino acids
• Each amino acid contains:
(1) Carboxylate group (-COO-)
(2) Amino group (-NH2)
(3) Side chain (R) unique to each amino acid
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Fig 1.3 Structure of an amino acid
and a dipeptide
(a) Amino group (blue), carboxylate group (red)
(b) Dipeptides are connected by peptide bonds
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Polypeptides
• Polypeptides - amino acids joined end to end
• Conformation - the three dimensional shape of
a protein which is determined by its sequence
• Active site - a cleft or groove in an enzyme that
binds the substrates of a reaction
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Fig 1.4 Egg white lysozyme
(a) Free enzyme
(b) Enzyme, bound substrate in active site cleft
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B. Polysaccharides
• Carbohydrates, or saccharides, are
composed primarily of C,H and O
• Polysaccharides are composed of saccharide
monomers
• Most sugar structures can be represented as
either linear (Fischer projection) or cyclic
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Fig 1.5 Representations of the
structure of ribose
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Fig 1.6 (a) Glucose, (b) Cellulose
Glycosidic bonds
connecting glucose
residues are in red
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C. Nucleic Acids
• Polynucleotides - nucleic acid biopolymers
are composed of nucleotide monomers
• Nucleotide monomers are composed of:
(1) A five-carbon sugar
(2) A heterocyclic nitrogenous base
(3) Phosphate group(s)
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Fig 1.7 Deoxyribose
• Deoxyribose lacks a hydroxyl group at C-2.
It is the sugar found in DNA.
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Nitrogenous bases
• Major Purines:
Adenine (A)
Guanine (G)
• Major Pyrimidines
Cytosine (C)
Thymine (T)
Uracil (U)
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Fig 1.8 Adenosine Triphosphate (ATP)
• Nitrogenous base (adenine), sugar (ribose)
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Fig 1.9 Structure of a dinucleotide
• Residues are
joined by a
phosphodiester
linkage
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Fig 1.10 Short segment
of a DNA molecule
• Two polynucleotides
associate to form a
double helix
• Genetic information is
carried by the sequence
of base pairs
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