1 There are millions of protiens in the body. They're the most abundant molecule in cells making up
about 50% or more of a cells dry mass.
2 AMINO ACIDS
2.1 Protiens are made from long chains of AMINO ACIDS.
These are called MONOMERS, the smaller molecules
which linked together create a protein. Two AMINO
ACIDS join together and form a DIPEPTIDE. More
than two aminoacids form a polypeptide. One or more
polypeptide form proteins.
2.1.1 Different amino acids have different VARIABLE
GROUPS, all amino acids have the same general
structure, a CARBOXYL GROUP (-COOH) and an
AMINO GROUP (-NH2) attached to a CARBON. The
difference is the VARIABLE GROUP, represented by
an R in a diagram.
220.127.116.11 Amino acids link together through PEPTIDE BONDS
and form dipeptides and polypeptides. Like
CARBOHYDRATES and TRIGLYCERIDES,
dipeptides and polypeptides are formed by
3 STRUCTURAL LEVELS
3.1 Proteins have four STRUCTURAL LEVELS.
3.1.1 PRIMARY STRUCTURE: This is the sequence of
AMINO ACIDS in the POLYPEPTIDE CHAIN.
3.1.2 SECONDARY STRUCTURE: The polypeptide chain
does not remain flats. This is because HYDROGEN
BONDS for between the AMINO ACIDS in the chain.
This makes it automatically coil into an ALPHA HELIX,
or fold into a BETA PLEATED SHEET.
3.1.3 TERTIARY STRUCTURE: The coiled or folded chain
of amino acids is often coiled and folded further. This
causes more bonds to form between different parts of
the POLYPEPTIDE CHAIN. However proteins formed
from only one polypeptide chain develop their final 3D
STRUCTURE in the TERTIARY STRUCTURE.
3.1.4 QUATERNARY STRUCTURE: For the proteins which
are made of many POLYPEPTIDE CHAINS, this is
the way that they are assembled together. Proteins
made from MORE THAN ONE POLYPEPTIDE
CHAIN form their final 3D STRUCTURE in the
3.2 STRUCTURAL LEVELS AND THEIR BONDS
3.2.1 PRIMARY STRUCTURES are held together by
3.2.2 SECONDARY STRUCTURES are held together by
HYDROGEN BONDS that form nearby amino acids.
These bonds create ALPHA HELIX CHAINS, or BETA
3.2.3 TERTIARY STRUCTURE. These are affected by
numerous types of bonds. IONIC INTERATIONS.
These are weak attractions between the negative and
positive charges on different parts of the molecule.
DISULFIDE BONDS. Whenever molecules of
CYSTEINE come together, the SULFUR ATOM in one
cysteine bonds to the sulfur of the other cysteine
forming a DISULFIDE BOND
3.2.4 HYDROPHOBIC AND HYRDOPHILLIC
INTERACTIONS. This is when the HYDROPHOBIC
groups clump together in the protein, the means that
the HYDROPHILLIC groups are pushed to the outside
this affects how the protein folds up into its final
3.2.5 QUATERNERY STRUCTURE. This can be
influenced by all the forms of bonds mentioned
above. This is often determined by the TERTIARY
STRUCTURE of the individual polypeptide chains
being bonded together
3.3 3D STRUCTURE AND PROPERTIES
3.3.1 The amino acid sequence of a protein determines
what bonds will form and how the protein will fold up.
In turn the 3D structure of a protein will determine its
3.3.2 Protein 3D Structures can be Globular or Fibrous
3.3.3 GLOBULAR: Globular proteins are round, compact
proteins made of many polypeptide chains, these
chains are coiled up so that the hydrophillic parts are
on the outside, where as the hydrophobic parts are on
the inside. This means that the protein in SOLUBLE,
and can be transported easily. E.G Haemoglobin is a
globular protein madeof 4 polypeptide chains, it carries
oxygen and is carried in the blood. It contains HAEM
groups which bind to oxygen
3.3.4 FIBROUS: Fibrous proteins are made of long,
insoluble polypeptide chains, that are tightly coiled
to form a rope shape. These are held together by
lots of bonds, these fibrous proteins are strong and
the means they are often found in supportive
tissue. For example, collagen, which is a strong
protein that forms supportive tissue in animals.