Tertiary Structure. A result of interactions between side (R) chains that are widely separated within the peptide chain Covalent disulfide bonds - between 2 cysteine AA Salt bridges - between AA w/ charged side chains (acid & base AA) Hydrogen bonds - between AA with polar R groups
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Covalent disulfide bonds - between 2 cysteine AA
Salt bridges - between AA w/ charged side chains
(acid & base AA)
Hydrogen bonds - between AA with polar R groups
Hydrophobic attractions - between NP side chains
Tertiary protein structure bonding
3o protein structure - Non-covalentR group interactions:
(a) electrostatic interaction
(b) hydrogen bonding
(c) hydrophobic interaction
found mainly in
where it serves
as an intracellular
When O2 binds to
Fe of Heme group,
tension on the
an amino acid,
which alters the
3o structure –
This in turn affects the 4o structure bonds Exposes more heme sites -
creates greater affinity for O2
Two major types - based on structural levels
Fibrous - peptide chains are arranged in long strands/sheets
Globular - peptide chains are folded into spherical/globular shapes
Fibrous versus Globular protein
Have fiber-like structures – good structural material. Relatively insoluble in water.
Unaffected by moderate in temp and pH.
Subgroups within this category include:
Collagens & Elastins: the proteins of connective tissues. tendons and ligaments.
Keratins: proteins that are major components of
skin, hair, feathers and horn.
Fibrin: a protein formed when blood clots.
Myosin: a protein that makes up muscle tissue
In living organisms:
Serve regulatory, maintenance and catalytic roles.
Include hormones, antibodies, and enzymes.
Either dissolve or form colloidal suspensions in water.
Generally more sensitive to temperature & pH change
than fibrous protein counterparts.
Examples within this category include:
InsulinRegulatory – controls glucose levels
HemoglobinTransport – moves O2 around body
MyoglobinStorage – stores O2 near muscles
TransferrinTransport – moves Fe in blood
ImmunoglobulinsDefense – attacks invading pathogens
Nails Horn & Hoof feathers Hair
Keratin structural molecules are normally long and thin,
insoluble in water, very high tensile strength,and arranged to form fibers.
Composed of long rods, twisted together,
laid down in criss-cross matrix form.
Keratinized stratified squamous epithelial layer:
found only in skin!
Dead cell layers at surface. Keratin effectively waterproofs cells. Blocks diffusion of nutrients & wastes.
Provides protection against friction, microbial invasion, and desiccation.
Many cross-links create very little flexibility: horns, claws, hooves, or nails.
Fewer cross-links allows some stretching but returns to normal: wool, skin, and muscle proteins.
Fibrous structural protein: Collagen
Collagen exists as a molecule that is tightly coiled about itself forming a secondary triple coil.
The molecules bunch together in groups of three,
forming a larger coil (superhelical coil)
that gives collagen fibers their strength in living tissue.
Collagen structure can be disrupted
in diseases such as scurvy,
which is a lack of ascorbic acid, a cofactor
in the hydroxylation of proline (Hydroxyproline)
In addition, collagen structure is disrupted
in rheumatoid arthritis.
Muscle tissue contracts
and relaxes when
triggered by electrical
stimuli from brain.
Muscle fibers bundled
together make up a
single muscle. Many
myofibrils make up
striations, formed by
The protein forms filaments. 2 types of filament: thick & thin.
Thick filaments contain myosin; thin filaments contain
actin, troponin and tropomyosin.