Download Proteins: Their Bio-Chemistry and Functions

Proteins: Their Biochemistry
and Functions.
By: Quy Le (#6)
URL: http://proteins1.tripod.com
Organic Chem. 12 B
Spring-2005
Outline
I) History of proteins:
- Jöns Jacob Berzelius and Gerharus Johannes Mulder coined
the term “protein”.
- Investigation of proteins and their properties began 1800.
II) Protein’s structure:
- Many amino acid units link together to make up proteins.
- Primary structure: the linear arrangement of amino acids.
- Secondary structure: areas of folding or coiling.
- Tertiary structure: the final three-dimensional structure.
- Quaternary structure: non-covalent interactions.
III) Functions of Proteins:
- Enzymes (catalytic activity & function)*
- Transport Proteins ( bind &carry ligands)*
- Storage Proteins ( ovalbumin, gluten, ferreting)
- Movement (muscles; can contract)
- Mechanical support (collagen-bone, keratin)*
- Defensive-protect ( antibodies, bacterial toxins)
- Regulatory-signal ( metabolic, hormones)
- Receptors-detect stimuli ( membrane receptor,
and acetylcholine or insulin)*
IV) Disease Related with Proteins:
- Sickle cell disease
- Marfan Syndrome
- Diabetes
I. History of Proteins.
- It started from late 1700’s, Physiological chemists was trying
to understand the materials that made up living cells. They
identified albuminoids from coagulation of egg…
- In 1800’s, Chemists set out to identify the chemical makeup
of proteins (exp. Water= H2O; Methane= CH4)
- By 1838, a Dutch chemist, Gerardus Mulder presented is
finding that albuminoids had high quantities of nitrogen
and small amounts of sulfur.
http://www.madsci.org/posts/archives/feb98/888588800.Sh.r.html
- July 10, 1838, a Swedish biochemist Jöns Jacob Berzelius
suggested Mulder to give the albuminoids more special name
because it appear to be a principal substance of animal nutrition
the word Protein (meaning of primary importance) was used.
- In 1930s, the famous work of Moses Kunitz and John Hward
Northrop at the Institute in New York City convinced the world;
they studied three different chemical reactions came from three
different proteins.
-In 1953, Sanger’s experiments showed that proteins have a
unique amino acid sequence. He also showed for the first time
that all amino acids in mammalian proteins are in the Sconfiguration, peptide bond is an amide bond, and amino acids
have alpha amino groups and alpha carboxyl groups.
http://wiz2.pharm.wayne.edu/biochem/prot.html
II. Protein’s Structure:
- Proteins are very complicated
molecules. With 20 different
amino acids that can be arranged
in any order to made a
polypeptide of up to thousands of
amino acids long.
http:// www.chembio.uoguelph.ca/educmat/phy456/gif/peptide5.gif
A. Structure of Amino Acids in
Proteins:
- All amino acids found in proteins
have this basic structure,
differing only in the structure of
the R-group
1. A alpha hydrogen: H
2. A alpha amino group: -NH2
(basic)
3. A alpha carboxyl group: -COOH
(acidic)
4. A side chain: R (20 possible)
- Basic structure:
http://www.biology.arizona.edu/biochemistry/problem_sets/aa/aa.html
B. Stereo Configuration of Amino
Acids.
- All of the amino acids
used in proteins
(except for glycine
which is not optically
active) are of
L-configuration.
- However in R/S
notation Cysteine is
2R, whereas the
others are 2S.
http://bmbiris.bmb.uga.edu/wampler/tutorial/aaconfig.html
C. Classifying of Amino Acids
- The 20 different R
groups give
amino acids
individual
characteristic.
They are grouped
in four major
groups according
to their
characteristics.
http://www.ucl.ac.uk/~sjjgsca/ProteinStructure.html
D. Bonding in Amino Acids
- Polypeptides and proteins
are formed of chains of
amino acids joined
together by linkages called
peptide bonds.
- Peptide bond formation is
an example of a
condensation reaction ,
whereas a molecule of
water is released.
http://saints.css.edu/bio/schroeder/proteins.
html
- Peptide Bond Formation:
E. Primary Structure of Proteins
- The primary structure of
a protein is its linear
sequence of amino acids
and the disulfide (-S-S-)
bridge; all covalent
connection in a protein.
- The amino terminal or
“N-terminal”(NH3+) at
one end; carboxyl
terminal “C-terminal”
(COO-) at the other end.
http://users.rcn.com/jkimball.ma.ultranet/
BiologyPages/P/Polypeptides.html
F. Secondary Structure of Proteins
- Alpha-helix: described by
Linus Pauling; has a rod
shape. The peptide is coiled
around like a cylinder and
stabilized by H-bonds
formed between peptides
- Beta-pleated sheets: adopt
the conformation of a sheet
of paper and the structure is
stabilized by H-bonds
between amino in different
polypeptide strands.
http://www.rothamsted.bbsrc.ac.uk/notebook/c
ourses/guide/prot.htm#II
http://www.ekcsk12.org/science/apbio/bioche
mnts.html
G. Tertiary Structure of Proteins
- Tertiary structure is the way
the secondary structure
fold onto themselves to
form a protein or a
subunit of a more
complex protein
- Amino acids which are very
distant in the primary
structure might be close in
the tertiary one because of
the folding of the chain.
http://www.rothamsted.bbsrc.ac.uk/noteboo
k/courses/guide/prot.htm#II
http://www.ekcsk12.org/science/apbio/bioche
mnts.html
H. Quaternary structure of Proteins
http://www.ekcsk12.org/science/apbio/biochemnts.html
- Complexes of 2 or more
polypeptide chains held
together by noncovalent
forces but in precise ratios
and with a precise 3-D
configuration.
- A good example is the
quaternary structure of
hemoglobin, made up of
2 alpha and 2 beta
polypeptide chains.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/Q/QuaternaryStructure.html
III. Function of Proteins
A. Proteins as catalyst
- Proteins that act like catalysts in chemical reactions are
called enzymes.
- Enzymes are the catalysts which make possible
biochemical reactions. Catalyst increase the rate of a
reaction, but are not themselves consumed or produced
by the reaction.
- Enzymes are grouped into six classes according to the
kind of reaction they catalyze
http://courses.cm.utexas.edu/jrobertus/ch339k/overheads-2/ch8_enzyme-classes.jpg
B. Receptors
- Proteins in the Plasma
Membrane include:
1. Transport channel (D),
which ions and
macromolecules may pass
2. Enzymes (I): provide a
convenient surface for
enzymes to be embedded.
3. Cell surface receptors (B):
fit only to specific
substances.
4. Cell surface identity
markers (E): each cell
carries its own ID markers
5. Cell adhesion proteins (A):
adjacent cells stick together
via interlocking proteins on
their membranes.
http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/c
ells/notes/ch6/ch6menu.htm
C. Transport Protein - Hemoglobin
- Hemoglobin is a protein
that is carried by red cells.
It picks up oxygen in the
lung and delivers it to the
tissues to maintain the
viability of cell.
- Hemoglobin is made from
two similar proteins that
stick together.
http://www.medicaldefinitions.net/hemoglobin.htm
http://www.chem.purdue.edu/chm333/hemoglobin
.JPG
D. Mechanical support
- About one quarter of all of the
protein in our body is collagen.
- Collagen provides structure to
our bodies, protecting and
supporting the softer tissues
and connecting them with the
skeleton.
- Collagen is composed of 3 chains,
wound together in a tight triple
helix. Every third amino acid is
a glicine, and many of the
remaining amino acids are
proline or hydroxyproline.
http://www.rcsb.org/pdb/molecules/pdb4_1.html
IV. Disease Related with Proteins
A. Sickle Cell Disease
- Sickle cell disease a genetically
disorder affecting 1out of 10
African Americans.
- Disease is cause by mutation in
the gene responsible for the
production of hemoglobin.
Substitution of a single amino
acid ( valine for glutamic acid) in
the sixth position of the Bchain of the hemoglobin
molecule produces a
hydrophobic.
- The defective hemoglobin forming
long rods that stretch a red
blood cell into a crescent too
large to fir through small blood
vessels.
http://encarta.msn.com/media_681500788/SickleCell_Anemia.html
http://www.coe.neu.edu/research/berl/BERL_resear
ch_sicklecell.html
B. Marfan Syndrome
- Marfan syndrome is a heritable (in 75%)
disorder of connective tissue that
affects many organ systems
including the skeleton, lung, eyes, heart
and blood vessels. Affect both men
and women, of any race and ethnic
group. They are typically very tall,
slender, and loose jointed
- In Marfan syndrome a protein called
fibrillin is deficient or abnormal.
Fibrillin is part of elastic fibres,
accounting for the unusual stretchiness
and weakness of tissues.
- A mutation in the fibrillin gene on
chromosome 15 is said to be
responsible for the production of
abnormal fibrillin molecules which
can’t function properly.
http://www.nlm.nih.gov/medlineplus/ency/imagepages/9611.htm
http://www.marfan.net.au/showcontent.toy?cid=1515
C. Diabetes
- Diabetes occurs when the
body can't produce enough
insulin, or when the insulin
that the body makes does
not work properly.
- Type 1 Diabetes: because
the insulin-producing cells
of the pancreas are
destroyed by the immune
system. People with type 1
diabetes produce no
insulin and must insulin
injection to control their
blood glucose.
http://my.webmd.com/content/article/46/1667_50911?src
=pemedscape
Type 2 Diabetes
- People with type 2 diabetes produce
insulin. However, the insulin their
pancreas secretes is either not
enough or the body is unable to
recognize and use it properly.
- When there isn’t enough insulin or
the insulin is not used as it should
be, glucose can’t get into the
body’s cell.
- It affects 18 mill. Americans; usually
occurs in people over age 40 who
are overweight.
http://my.webmd.com/content/article/46/1667_50911?src=pemedscape
Conclusion
- Proteins are one of the classes of biomacromolecules, that make up the primary
constituents of living things.
- They are essential to the structure and funstion
of all living cells and viruses.
- They are amongst the most actively studied
molecule in biochemistry .
V. References
-
http://www.madsci.org/posts/archives/feb98/888588800.Sh.r.html
-
http://wiz2.pharm.wayne.edu/biochem/prot.html
-
http://www.chembio.uoguelph.ca/educmat/phy456/gif/peptide5.gif
http://www.biology.arizona.edu/biochemistry/problem_sets/aa/aa.html
-
http://bmbiris.bmb.uga.edu/wampler/tutorial/aaconfig.html
-
http://www.ucl.ac.uk/~sjjgsca/ProteinStructure.html
-
http://saints.css.edu/bio/schroeder/proteins.html
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Polypeptides.html
-
http://www.ekcsk12.org/science/apbio/biochemnts.html
-
http://courses.cm.utexas.edu/jrobertus/ch339k/overheads-2/ch8_enzyme-classes.jpg
http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/cells/notes/ch6/ch6menu.htm
-
http://www.chem.purdue.edu/chm333/hemoglobin.JPG
-
http://www.rcsb.org/pdb/molecules/pdb4_1.html
-
http://www.coe.neu.edu/research/berl/BERL_research_sicklecell.html
-
http://my.webmd.com/content/article/46/1667_50911?src=pemedscape