Download The 20 amino acids

Molecules of Life
Chapter 2
Protein Functions
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Act as enzymes
Structural- cytoskeleton (actin, tubulin, others)
Mechanical- actin and myosin in muscle
Cell signaling
Immune responses
Cell adhesion
Cell cycle
transport
The 20 amino acids
You don’t
Have to
memorize
these
Proteins
 Built from 20 common monomers called amino
acids (aa)
Peptide bond
Amino acid = monomer
aa
aa
aa
aa
aa
aa
polypeptide=polymer
Polypeptide- A chain of amino acids bonded together
by peptide bonds in a condensation reaction
aa
Peptide Bond Formation
A DNA encodes the
order of amino acids in a
new polypeptide chain.
Methionine (met) is
typically the first amino
acid.
B In a condensation reaction, a peptide bond
forms between the methionine and the next amino
acid, alanine (ala) in this example. Leucine (leu)
will be next. Think about polarity, charge, and
other properties of functional groups that become
neighbors in the growing chain.
Fig. 3-16a, p. 44
C A peptide bond forms between the
alanine and leucine.
Tryptophan (trp) will be next. The chain
is starting to twist and fold as atoms
swivel around some bonds and attract or
repel their neighbors.
D The sequence of amino acid
subunits in this newly forming peptide
chain is now met–ala–leu–trp. The
process may continue until there are
hundreds or thousands of amino acids
in the chain.
Stepped Art
Fig. 3-16b, p. 45
Globin Chains in
Hemoglobin
Molecular Basis of Sickle Cell
Anemia
valine
histidine
leucine
threonine
proline
glutamic
acid
glutamic
acid
A Normal amino acid sequence at the
start of the hemoglobin beta chain.
Fig. 3-19a, p. 47
Molecular Basis of Sickle Cell
Anemia
valine
histidine
leucine
threonine
proline
valine
glutamic
acid
B One amino acid substitution results in the abnormal
beta chain of HbS molecules. The sixth amino acid in
such chains is valine, not glutamic acid.
Fig. 3-19b, p. 47
Nucleotides
Nucleotide (the monomer of nucleic acid)
Monomer
Two kinds of nucleic
acids:
RNA
DNA
Four Nucleotides of DNA
The DNA
Molecule
covalent
bonding in
sugar–
phosphate
backbone
hydrogen bonding
between bases
Fig. 3-22, p. 49
Nucleic acids
Proteins
Lipids
Nucleic AcidsInformational
Polymers
Summary:
Organic Molecules in Living Things