The proteins primary structure refers to a long sequence of
amino acids within a peptide chain. The first structure is held along by
peptide bonds that are created through the method of protein biosynthesis. The
first structure of a protein is decided by the gene similar to the protein. A
particular sequence of nucleotides in DNA is transcribed into mRNA, which is
read by the ribosome during a method which is known as translation. The
sequence of a protein is unique to that protein, and defines the structure and
function of the protein. The sequence of a protein can be determined by methods
such as mass spectrometry. However, it can also be read directly from the
sequence of the gene using the genetic code. Amino acid residues are important
as when a peptide bond is made, a water molecule is lost, and so proteins are
created of amino acid residues.
Secondary structure refers to pleated structures that form
within a polypeptide because of interactions between atoms of the backbone.
(The backbone refers to the polypeptide chain except for the R groups). The
common forms of secondary structures are the ? helix and also the ? helix folded
sheet. Each structure is held in their place by hydrogen bonds that form
between the carbonyl O of one amino acid and also the amino H.
In an ? helix, the carbonyl C=O of one amino acid is bonded
with hydrogen to the amino H (N-H) of an amino acid. (The carbonyl of amino
acid one would form a hydrogen bond to the N-H of amino acid five.) This
pattern of bonding puts the polypeptide chain into a helical structure that
resembles a curly ribbon. The R groups of the amino acids stick outward from
the ? helix, wherever they’re free to move. In a ? folded sheet, two or more
segments of a polypeptide chain line up next to every other, forming a
sheet-like structure held along by hydrogen bonds. The hydrogen bonds form
between carbonyl and amino groups of backbone, whereas the R groups extend
above and below the plane of the sheet.
The three-dimensional structure of a polypeptide chain is
named its tertiary structure. The tertiary structure is primarily a result of
interactions between the R groups of the amino acids that put together a
specific protein. R group interactions that contribute to tertiary structure
include hydrogen bonding, ionic bonding, dipole-dipole interactions, and
dispersion forces. for instance, R groups with like charges repel each other,
whereas those with opposite charges will form an ionic bond which will then
attract. Polar R groups will type hydrogen bonds and alternative dipole-dipole
interactions. Tertiary structures are hydrophobic interactions, during which
amino acids with nonpolar, hydrophobic R groups form together on the inside of
the protein, leaving hydrophilic amino
acids on the outside to act with the surrounding water molecules.
Many proteins are created of one polypeptide chain and have
only three levels. However, some proteins are created from multiple polypeptide
chains, additionally called subunits. once these subunits come together, they
provide the protein its quaternary structure. haemoglobin contains a quaternary
structure. haemoglobin carries oxygen within the blood and is formed of four
subunits, two each of the ? and ? types. Another example is DNA polymerase, an
enzyme that synthesizes new strands of DNA and consists of 10 subunits. In
general, similar kinds of interaction that contribute to tertiary structure
(mostly weak interactions, like hydrogen bonding and dispersion forces)
additionally hold the subunits along to present quaternary structure.
Cellulose consists of a long chain of many glucose
molecules. cellulose is a polysaccharide that is a kind of sugar. many of those
polysaccharide chains are organized parallel to create polysaccharide
microfibrils. The individual polysaccharide chains are bound along within the
microfibrils by hydrogen bonds. The microfibrils are place along to create
macrofibrils. The microfibrils of cellulose are very powerful and inflexible
because of the presence of hydrogen bonds. Their arrangement is crystalline,
which means that the microfibrils have crystal-like properties. cellulose is a
polysaccharide that contains a structural role in animals and plants. In
plants, cellulose is the compound that provides rigidity to the cells. The
bonds between every cellulose molecule are very strong, which makes cellulose
very hard to break down. cellulose is found in plant cell walls, where it
provides structure andl support. cellulose fibres are held along by pectin
fibres, that bind the cellulose along to create even tighter cell walls in
plants which provides them good strength.
Haemoglobin is an oxygen carrying pigment, that is present
in red blood cells. It has 2 components. One is named haem that is a prosthetic
group. and therefore the alternative component is goblin protein. haem
containing proteins are present in aerobic animals and helps with the transport
of oxygen. haem part is same in all the animals. The difference is in the
globin chains is that they need completely different amino acids in numerous
animals. haem has one central iron, that is connected to four pyrol rings. The
pyrol rings are connected by methylene bridges. Globin is the protein part and
contains of four chains. In human, there are 2 alpha chains and other two may
be beta, delta, gamma or epsilon depending on the type of haemoglobin.
The main function of haemoglobin is to carry oxygen from the
lungs to all the tissues of the body. once a haemoglobin comes in contact with
oxygen, it combines with it and form oxy-haemoglobin. this can be a week bond.
once blood reaches to tissues, wherever oxygen is deficient, the bond is broken
and oxygen diffuses out to tissues. a number of CO2 is transported from tissues
to lungs through haemoglobin though the majority of it is transported via
plasma. The red colour of blood is as a result of haemoglobin. haemoglobin
additionally acts as a buffer. Buffer means that to resist modification in pH.
Blood has 7.4 pH and it remains within the range as a result. If the pH changes
the lifetime of the person could also be endangered. Therefore, haemoglobin
plays important role to keep the pH of blood correct and in its range of pH.