Transport proteins like hemoglobin and myoglobin carry oxygen in the bloodstream and muscles. Hemoglobin contains four chains that carry oxygen, changing shape as they bind and release oxygen levels in tissues. Storage proteins like ferritin, casein, and ovalbumin store minerals and amino acids to provide reserves for growth and development. Ferritin stores iron safely in the body, and casein and ovalbumin store amino acids found in milk and egg whites. Plant storage proteins make up a large portion of seeds and provide nutrition for germinating seeds and humans.

1. University
Of Sargodha
Name: Sonia Gulzar
Roll no:
80
Class:
B.S Botany 6th
semester
SS
Topic: Transport and Storage Proteins
Submitted to: Mam Naima

2. Transport And Storage Proteins
Transport Proteins
Carrier Molecules
The next broad category of proteins we will consider are
the carrier molecules or transport proteins. These transport
proteins are often globular proteins. They are generally tightly
packed with polar side groups on the outside to enhance their
solubility in water. They typically have nonpolar side groups
folded to the inside to keep water from getting in and unfolding
them.
Serum albumin is one example. It transports water-insoluble
lipids in the bloodstream.
Hemoglobin
Hemoglobin is another example. It carries oxygen from the
lungs to the tissue. Myoglobin performs a similar function in
muscle tissue, taking oxygen from the hemoglobin in the blood
and storing it or carrying it around until needed by the muscle
cells.
Hemoglobin and myoglobin also have similar structures.
Myoglobin contains 151 amino acid residues plus a heme group
to bond to oxygen. Hemoglobin has four similar chains, two
with 141 residues and a heme group and two with 146 residues

3. and a heme group. The molecular weight of hemoglobin is about
64,500 and can carry four oxygen molecules.
It is important that hemoglobin can bond to oxygen under
certain conditions. But it is equally important that hemoglobin
can release oxygen under other conditions. The ability of
hemoglobin to bind oxygen is sensitive to several factors. They
include pH, temperature, concentrations of O2 and CO2, and
even the number of oxygen molecules already bound. It seems
that when oxygen binds to hemoglobin, the structure of the
hemoglobin changes slightly in a way that makes it better at
binding to more oxygen, thus enhancing its ability to carry more
oxygen.
Oxygen Binding Curve
The partial pressure of the oxygen in the body tissues is about 40
mm Hg or less, which is partway down the steep part of the
graph. Thus, in the lungs, virtually all of the hemoglobin bonds
to oxygen and the blood becomes rich in oxygen, turning a
characteristic red color. When the blood reaches active body
tissue, the hemoglobin releases a fair amount of its oxygen
because of the low partial pressure of oxygen in the tissue and it
turns the blue color characteristic of venous blood. Hemoglobin
generally retains about half to three-quarters of its oxygen in
venous blood, rather than giving it all to the cells under normal
conditions. The value of this is that some reserve oxygen is

4. available from the hemoglobin when strenuous exercise depletes
the cellular oxygen to even lower partial pressures.
Hemoglobin can be used as an example to point out how
important the conformation of a protein is. The shape and the
functional groups must be such that they will attract oxygen
molecules, but not nitrogen molecules (which are four times
more abundant in air than are oxygen molecules), and not water
molecules, and not sugar molecules, and so on. Ironically,
another molecule, carbon monoxide, will bind to hemoglobin
200 times more readily than oxygen. That makes carbon
monoxide very dangerous. Not only does the hemoglobin that
has bonded to carbon monoxide not have oxygen to give to the
cells, it cannot easily get rid of the carbon monoxide to be able
to get some oxygen.
Sickle Cell Hemoglobin
The disease sickle cell anemia points out another important
aspect of protein structure. As you know, the primary structure
of a protein determines the secondary structure which
determines the tertiary structure and the quaternary structure,
which in turn determines the function of the protein. In sickle
cell hemoglobin the sixth amino acid residue is valine instead of
glutamic acid. That's it. That's the difference.
The consequence is that when the hemoglobin releases its
oxygen, it reacts with other such proteins in a way that causes
the shape of red blood cells to change. The red blood cells

5. change to a sickled shape which does not readily pass through
capillaries and thus causes a number of problems.
Linus Pauling, who helped uncover the alpha-helix primary
structure of proteins, refers to diseases such as this as "molecular
diseases." The change of a single amino acid in a protein, by the
way, does not always have such a drastic effect on the function
of the protein.
Cytochromes
Another quite different group of carrier molecules is the group
known as the cytochromes. These are the electron carrier
proteins that operate in the electron transport chainwhich is part
of the respiration process. They carry electrons from the
hydrogen atoms freed in the citric acid cycle to waiting oxygen
molecules. At the end of that process, the hydrogen and oxygen
combine to form H2O. The energy released in this series of
reactions is stored by using it to convert ADP to ATP.
"Inhibition" of Carrier Proteins
Carrier proteins can be affected by what can be
called competitive inhibition.
For example, hemoglobin is a carrier protein that transports
oxygen from the lungs to muscle tissue and other cells.
However, carbon monoxide molecules compete with oxygen for
the binding sites on the hemoglobin molecule. If they are present

6. in high enough concentration, they prevent sufficient oxygen
from getting to the tissues and the organism dies.
Cyanide is another poison that affects respiration. It acts
by inhibiting the cytochrome proteins that are an integral part of
the electron transport system in respiration.
Storage Proteins
Storage proteins are a source of amino acids for growing
organisms,such as this germinating garden pea.Storage
Proteins - store amino acids.Examples include ovalbumin and
casein.Ovalbumin is found in egg whites and casein is a milk-
based protein.
Storage proteins serve as reserves of metal ions and amino acids,
which can be mobilized and utilized for the maintenance and
growth of organisms. They are particularly prevalent in plant
seeds, egg whites, and milk.
Perhaps the most thoroughly studied storage protein is ferritin,
which stores iron. Iron is a mineral required by all living things;
it is a component of heme, which is found in the transport
protein hemoglobin, as well as of cytochromes, molecules taking
part in cell metabolism (including drug metabolism). Free iron
in solution, on the other hand, is able to participate in free
radical reactions that damage proteins, lipids , and nucleic acids.
Therefore, within organisms, in addition to serving as an iron
reserve, ferritin provides a safeguard against potentially harmful
side effects of iron.

7. Ferritin is a complex of 24 polypeptide chains that form a nearly
spherical shell around a core of up to 4,500 iron atoms stored as
iron oxide–hydroxide (ferrihydrite) complexes. Ferritin is able to
store and release iron in a controlled fashion.
Proteins are made from amino acids, and many storage proteins
serve as reserves of amino acids in embryonic and developing
organisms. This is true of both animals and plants. Two well-
known storage proteins in animals are casein and ovalbumin.
Casein, found in mammalian milk, and oval-bumin, found in egg
white, both provide a de
veloping organism with a ready source of amino acids and
organic nitrogen.
Plant storage proteins are found in high concentrations in seeds,
especially in leguminous plants, in which the storage proteins
constitute up to 25 percent of the dry weight of the seed. These
proteins have no known enzymatic function and often exist
within separate vesicles (packets) in the seeds. In addition to
their importance to the germinating seed, these plant storage
proteins are a valuable source of human nutrition.

8. Reference
http://www.chemistryexplained.com/St-Te/Storage-
Protein.html#ixzz31CJddhP4
www.wikipedia,com