Bio3400
Chapter 14
Translation and Proteins
Translation requires
acids,
RNA (mRNA),
ribosomes,
and
RNA
( tRNA ).
Each tRNA is "charged" with a specific amino acid by 20 different aminoacyl
tRNA
.
Translation of mRNA can be divided into three steps.
requires
the
and
ribosomal subunits, GTP, initiator tRNA, and
initiation
.
requires both ribosomal subunits assembled with the mRNA to form the
site and
site.
is signaled by a
codon (UAG, UAA, UGA) in the A
site.
A mRNA molecule can have several
simultaneously translating the message, forming
(
polysomes
).
Review: interactive polypeptide
coding,
translation
steps,
animation.
Studies of mutations that result in heritable human diseases such as
and
provided first insight into the role of
proteins
in genetic processes.
Studies of mutations in
Neurospora
led to the one-gene:one-
hypothesis.
Studies of human
showed that one
gene
encodes one
.
Humans possess
different hemoglobin polypeptide
genes;
two of which are expressed at different times in development
The order of nucleotides in a gene is
with the order of amino acids in the corresponding
polypeptide.
Amino acids are composed of a
group, an
group, and an R group bound to a central
atom.
The
structure of a polypeptide is the sequence of amino acids formed by linking them together by
bonds.
Proteins may also exhibit
additional levels of structure:
secondary,
tertiary,
and
quaternary.
Proteins play diverse roles in the body.
Hemoglobin
binds to and transports
, which is essential for cellular metabolism.
Collagen
and
keratin
are
proteins.
Actin and
myosin
are
proteins in muscle tissue.
(
antibodies
) recognize "foreign" particles in the immune system.
Transport
proteins move molecules across
.
Some
and their
receptors
are proteins.
bind to
DNA
in eukaryotic organisms.
Enzymes
act as
in biological reactions.