Consists of 4 protein molecules which are two ?-helices
and two ?- helices.  It can be found in
red blood cells and assists with transporting oxygen and carbon dioxide around
the body.  (Davis. C 2017)





Chemical reactions that happen in cells can have an
increased rate of speed by biological molecules called enzymes.  In the body, processes like digestion and
metabolism are aided by enzymes.  They
also bind molecules together and make some smaller so they all become easier to
manage and transport.  (Castro. A 2014)

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Needed by the immune system to help protect the
body, bacteria and viruses are picked up by the antibodies, which are proteins
in a large Y shaped structure.


Biological processes that need to happen between
various cells are signaled by proteins and some hormones.


Small molecules and atoms from cells can be carried
around the body using proteins.


In cells, proteins offer the support and structure
that they require.

Structural component

The way multiple polypeptide chains are arranged in
a protein is called a quaternary structure, but each protein still has a
specific sequence.  It normally consists
of 2 lighter, and 2 heavier chains that are stabilized with multiple hydrogen

Quaternary structure

The 3-D structure of a protein overall that is held
together by hydrogen bonds between the two chains that are positively and
negatively charged.  Disulphide bridges
form between two amino acids to help reinforce the structure.  Unlike the secondary structure, the R groups
of amino acids move towards the center of the structure to avoid any water that
may be present within the structure. (Khan academy 2017)

Tertiary structure

Two 3-D helices that pull together form the
secondary structure.  If the chain has a
spiral like shape, it is called an ?- helix, which occurs when the polypeptide
has a repeated pattern, but if it has a folded or pleated shape, it is known as
a ?-helix.  This happens because of the
hydrogen bonds, which provides stability to the structure as there are so
many.  In an ?-helix, the R groups of
amino acids all point towards the outside of the helix.

Secondary structure


The sequence of amino acids are different between
each protein depending on their purpose and size.  A dipeptide bond occurs when two amino acids
bond together, but more than two then become polymerization, and a polypeptide
is created when hundreds of amino acids bond, and the DNA decides the order of
the amino acids which provides us with the primary structure.

Primary structure


With twenty types of amino acids, they can be
combined in varied sequences to produce proteins which depends on the 3-D
structure and the purpose of the protein. 
The foods we eat can provide us with 9 of the amino acids our body requires,
and the remaining 11 can be produced by our body’s.






(The Columbia encyclopedia 2017)

Pyrimidines are a heterocyclic
organic compound containing 2 nitrogen atoms at 1 & 3.

Purines are a heterocyclic organic compound consisting
of a pyrimidine ring & imidazole ring.

Each cell in the body contains around 2M of DNA. If all the DNA in the
body was stretched out, it would reach to the moon and back 8000 times.   (Helmenstine. A, 2017)

Did you know…


After transcription, mRNA takes the copied genetic
codes, (RNA) and decodes it in to the desired sequence which forms a
polypeptide chain of amino acids which happens in the cytoplasm.  Translation also ends at the termination
stage where it will receive a signal for it to end it cycle.  (Biology-online dictionary, 2017)  



This is when DNA is copied and a strand of RNA is
formed.  This is completed by polymerases
which are also known as enzymes, and occurs for each gene separately.  This process ends at the termination stage
which produces a signal that tells the transcript that is job is done, but this
varies depending on the sequences it is signaling.  (Khan academy 2017)


DNA is responsible for genetic characteristics and
is the main component of chromosomes. 
Two nucleotides twisted around each other, similar to a ladder,
consisting of deoxyribose and phosphate and bases A, G, C, and T, together
create DNA.  The sequence that contains
the encoded genetic information is transcribed as the strands of DNA unwind and
are replicated.



An organic base consisting of adenine, guanine,
cytosine, uracil, and pentose sugar (Ribose) nucleotides together form a single
strand polymer which presents itself as RNA. 
It is used in the body for processes like coding and regulation.  mRNA (Messenger) is responsible for carrying
codes from the nucleus to the cytoplasm. 
(Britannica 2017) rRNA is a
complex molecule created with double and single helices and is required for
protein synthesis.  tRNA- There are 20
varieties of tRNA, and each one carries a different amino acid can be found in
the shape of a clover leaf with the end of one chain ending in C, C, A, which
is known as the anticodon, which connects with mRNA during synthesis.  (Toole & Toole 1999)



The structure of a single nucleotide consists of
three properties.  Phosphoric acid,
pentose sugar, and an organic base. 
Condensation reactions allow these three elements to combine and become
a nucleotide.  When two nucleotides bond
together, a dinucleotide is formed, and re-occurring condensation reactions
create a polynucleotide which is a long chain of nucleotides that have hydrogen
bonds between carbons 1 and 5, and when sugar and phosphate join, it is then
known as a phosphodiester bond.  (Toole
& Toole 1999)


Nucleic acids



In the body, some of the important molecules use
cholesterol as a building block so start from like bile acids and steroid
hormones which includes sex hormones.  It
is vital for the synthesis of vitamin D, which happens in the liver and cells,
and is obtained from your diet, and transported around your body by the blood
stream, and is also hydrophobic so it is insoluble.


Wax is highly insoluble, and at room temperature,
is more solid than oils.  It also
provides a waterproof layer that prevents water loss, and because it has
hydrophobic properties, it stops water from being absorbed.



Lipids provide the
body with nine calories per gram, making them the most energy rich component of

Did you know…


One fatty acid chain is replaced by a phosphate
base group which makes the head of the molecule soluble in water (Hydrophilic),
but the tails of the molecule are still insoluble in water (Hydrophobic), this
is known as an amphipathic molecule.  The
main component of the cell membrane is a phospholipid.  It is made up of a glycerol molecule and a phosphate
group, and form a double layer when many of them join up.  (Biology Dictionary (2017)


A glycerol molecule with three fatty chains
connected by covalent bonds, and are known as an ester bond which are formed
when a condensation reaction occurs. 
Each triglyceride contains a carboxylic acid group which can be found at
the terminal carbon atom and are normally made of around 14-22 carbons long.  They are hydrophobic which means they are
insoluble in water.  To prevent the
hydrogen bonds forming with the water molecules, the charges are distributed
evenly around the molecule. (A-Level
notes 2016)


As opposed to saturated fatty acids, unsaturated
fatty acids contain some double bonds. 
If only one double bond is present, it is known as monounsaturated, but
if more than one double bond can be found, then it is known as
polyunsaturated.  At room temperature,
fats with unsaturated tails are normally found as liquids which makes it
difficult for them to pack together tightly. 

Unsaturated fatty acids

A saturated fatty acid is composed of a chain
consisting of hydrogens and carbons connected by single bonds, and can be most
commonly found in the length of 18 bonds that can mainly be found in foods, and
at room temperature, is usually solid. 
(Mclaughin, 2017)

Saturated fatty acids

Lipids are a high energy source that are required for the
absorption of fat soluble vitamins. 
There are two main types of lipids; simple lipids and complex
lipids.  They are not soluble in water so
are known as hydrophobic, but are soluble in organic solvents like alcohol and
acetone.  Lipids also act as an
insulating layer under the skin to help keep the body warm.  Lipids are made from hydrogen and carbon
which gives them the name hydrocarbons.  “When metabolized, lipids are oxidized to release large amounts of
energy and thus are useful to living organisms Lipids are molecules that can be
extracted from plants and animals using nonpolar solvents such as ether,
chloroform and acetone” (Mandal, 2012)



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