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Deoxyribonucleic acid (DNA) is the making of inherited
genetic material inside each cell. An individual gene is a component for a DNA
molecule. Genes define which characteristics we inherit from each parent, also
by managing protein synthesis they often regulate activities which take place
within the brain. The structure of DNA is shown as a double helix, DNA has two
separate strands each of the strands have a backbone made up of different
groups such as sugar known as deoxyribose and phosphate groups. DNA links
molecules along its backbone using the four base pairs Adenine, thymine,
guanine and cytosine. These base pairs link using covalent bonds they hold
together in the centre by using hydrogen bonds the connecting holds the strand
of DNA in place and supports the twist of DNA from both sides. Hydrogen bonds
occur between the nucleotide base pairs two hydrogen bonds occur between
adenine and thymine and between cytosine and guanine. Hydrogen bonds are
exceptionally weak compared to covalent bonds this could be shown as the many hydrogen
bonds together present an extremely strong force that holds the two DNA strands
together, furthermore other groups of the base rings of polar groups can form
external hydrogen bonds with surrounding water that gives the molecule extra
stability. Phosphodiester bonds are the strong covalent bonds. DNA is the genetic code which is presented in
the form of nucleotides each individual cell are held in the correct place with
phosphodiester bonds. DNA is a polymer the phosphate
groups within these bonds move to the opposite ends of the DNA strand this is
due to the bonds being negatively charged. Phosphates can be held in
place by polyamines and metal ions, phosphates are neutralised by a protein
called histone. The phosphodiester bonds are produced by the linking of
phosphate`s and two free
hydroxyl groups of a deoxyribose molecule, due to the continuous linking this
creates a chain.


When a cell divides the hereditary information is then
transferred onto the next steps. Ribonucleic acid (RNA) this can transmit
instructions from the genes to aid each of the cells and the gathering of amino
acids into proteins. Nucleic acids were found within the nuclei of cells these
are molecules which contain carbon, oxygen, hydrogen, nitrogen and phosphorus. RNA
is formed from DNA, the genetic code is a copy of DNA, but it is not directly
translated into proteins, it goes through a process of conversion known as
messenger RNA (mRNA). Each of the molecule`s for mRNA encodes information for
just one protein with the sequence of three nitrogen containing bases in the mRNA
specifying an amino acid within the protein. The mRNA molecules are transported
through the nuclear envelope into the cytoplasm, where they are translated by
the rRNA of ribosomes. Amino acid chains are folded into varies shapes to form
proteins. The pentose sugar which is a monosaccharide carbohydrate plays an
important part in producing adenosine triphosphate commonly known as ATP this
is an energy source which provides energy within the cells. In DNA this is
called deoxyribose.  

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A chromosome
is a thread structure of nucleic acids and proteins which are found in the
nucleus of most cells, which carry genetic information in the form of genes.
DNA packaging is where each chromosome consists of one repeated thread like
molecule of DNA looped tightly around proteins and contains approximately
6,400.000,000 base pairs that make up DNA. The way it is packaged into chromatin
is a factor in how protein production is controlled. 

replication is where a cell makes an identical copy of its DNA

replication is the process by which a cell makes an identical version of its
DNA, this is determined at the beginning of every cell division therefore when
the cell divides each daughter cell will inherit an identical copy of the DNA. DNA
replication to be carried out the original DNA template would be needed as the
original copy of DNA is used to create a new DNA molecule. DNA nucleotides are
needed to form new strands, DNA polymerase is an enzyme that adds new
nucleotides to an expanding strand of DNA. An RNA primer is needed to start the
process as DNA polymerase can only add nucleotides to an existing strand of
DNA. An enzyme helicase is responsible for the unwinding of the double helix
structure. The denaturing temperature of DNA is dependent on three main
factors, one of these factors is the amount of guanine and cytosine. This is
because guanine and cytosine pairs have three hydrogen bonds while pairs of adenine
and thymine have only two hydrogen bonds. The second influence is the amount of
sodium. Sodium in increased levels supports the stability of the DNA double
helix on the other hand lower sodium levels makes the double helix less stable.
Lastly the length of DNA also effects melting temperature this is because a
longer DNA have more hydrogen bonds to break during denaturation.

DNA polymerase provides DNA nucleotides in a 5′ to 3′ direction. DNA
nucleotides are added to the exposed bases on both strands. Adenine pairs with
thymine, thymine with adenine, cytosine with guanine and guanine with cytosine.
A primer is needed to start replication. The Leading strand is synthesised
continuously. DNA polymerase adds nucleotides to the deoxyribose (3′) ended
strand in a 5′ to 3′ direction. The Lagging strand is synthesised in segments.
Nucleotides cannot be added to the phosphate (5′) end because DNA polymerase can
only add DNA nucleotides in a 5′ to 3′ direction. The lagging strand is
therefore synthesised in fragments. The fragments are then sealed together by
an enzyme called ligase. The two new strands twist
to form a double helix. Each is identical to the original strand. Translation
is the last stage from DNA to protein this process is the synthesis of proteins
directed by a messenger ribonucleic acid, the source found within the
nucleotide sequence of the MRNA are three letter words called codons each one is
known as one amino acid. The nucleotides are specified with the letters A, G, U and C. This is mRNA,
which uses uracil. Whereas DNA uses thymine.

Mutation is the changing of a structure of a gene, this is caused by an
alteration of the single base units in DNA. On the other hand, it could be the
deletion, insertion or rearrangement of sections of genes or chromosomes. Sickle
cell anaemia (SCA) is caused by a specific mutation within the haemoglobin Beta
gene this is found upon chromosome 11, haemoglobin is responsible for the
transportation of oxygen all around the human body. Normal red blood cells will
have haemoglobin A these will be smooth and round. The base sequence on the
MRNA which is produced by the DNA is altered, resulting in this a codon has been
changed, an alternate amino acid has been inserted into the protein chain. The
amino acid valine is inserted rather than glutamic acid, the protein
synthesised will no longer function correctly this sequence results in a sickle
cell shaped blood cell.  There are other
disorders which have resulted in a base change in the genetic sequence such as
cystic fibrosis and Tay-Sachs disease.

are lipids that play an important role within all cell membranes, they form a
lipid bilayer due to their amphiphilic characteristics. The structure of the
phospholipid molecule usually consists of two hydrophobic fatty acid tails and
a hydrophilic head which consists of a phosphate group. Phospholipids are like
triglycerides they have a glycerol backbone and two fatty acid chains which are
attached to the first two carbons. A phosphate group links a small charged
group that usually contains nitrogen to the backbone. The section of the
molecule which is the head is known as polar and can form hydrogen bonds with
water molecules, whereas the two fatty acids known as the tails are non-polar
and can interact only with other lipids.

The fluid mosaic
model relates to the cell membrane as being tapestry of several types of molecules
such as phospholipids, cholesterols and proteins they are moving all the time,
the constant movement aids the cell membrane to maintain its role as a barrier
between the inside and the outside of the cells environments. A monomer is a
basic unit which holds chemicals to other molecules to from a polymer, in this
case the monomers are glycerol and fatty acids. Some proteins in the membrane
are called Intrinsic. This means
that they span the Bilayer.
Others are called extrinsic they
are partly embedded in the
Bilayer. A very specific function of phospholipids is to form the phospholipid
bilayer of the plasma membrane. Within this bilayer, phospholipids are arranged
so that their hydrophobic tails are pointing inwards and their hydrophilic
heads are pointing outwards. This arrangement allows plasma membranes to be permeable
to solutes such as proteins and water.

Proteins are polymers, more so polypeptides these are formed from sequences
of monomer amino acids. If amyloid was to build up within the brain it
interferes with the neurons within the brain and its ability to send messages
throughout the body. Amino acids link together by peptide bonds as more get
added this becomes a polypeptide a protein is one or more polypeptide. A
primary structure is the linear sequence of an amino acid which is determined
by peptide bonds linking each amino acid. The secondary structure refers to the
linear sequence and how amino acids fold upon itself and determined by hydrogen
bonds also. There are two patterns one known as the alpha helix; if the
polypeptide wrapped around itself into a coil like structure this would be the
alpha helix hydrogen bonds run up and down the back bone stabilizing the structure.
The other pattern is known as the beta sheet this looks like a zig zag pattern
it is also stabilized by hydrogen bonds when an amino acid end lines up with a
carboxyl end it would show an anti-parallel configuration. A tertiary structure
is a higher order of the folding within a polypeptide chain this depends on
distant interactions. Hydrophobic packing is a folded-up protein this protein
would be found within the watery interior of a cell on the exterior of the
protein polar groups will be on the exterior interacting with water on the
interior you would find hydrophobic groups. Disulfide bridges can interact
between cystines this is a type of amino acid that have a phial group they have
a sulfur atom which can become oxidized when this oxidation occurs you get the formation
of a covalent bond between the sulfur groups the formation of a disulfide bridge
would happen on the exterior of cell. The separated phial groups would occur on
the interior of a cell this is because the interior of the cell has anti-oxidants
which produce a reduced environment and the exterior lacks anti-oxidants there
would be an oxidized environment therefore exocellular space favors disulfide

Quaternary structure is the bonding between multiple polypeptides, each
polypeptide is sub unit two sub units would be a dimer, three would be a trimer,
four would be a tetramer and anything above this would be called a multimer the
result of a folded protein is known as the conformation of a protein if any of
the three structures beforehand were to break down or misfolded which can then
contribute to various diseases. Proteins are responsible for transporting
substances across the cell membrane, they function as enzymes or receptors.

Carbohydrates are biomolecules which are composed by
carbon, hydrogen and oxygen. To represent the proportion of these elements with
the formula CH2O. Most carbohydrates are characterized
as monosaccharide, disaccharide or polysaccharide. The term saccharide means
sugar.  Monosaccharides are the monomers
of carbohydrates this includes glucose, fructose and galactose. Alpha glucose is a monomer unit which is present in starch,
due to the bonding in the alpha linkage starch also known as amylose forms a
spiral like structure. Beta glucose is the monomer unit within cellulose because
of the beta linkage cellulose is a linear chain. Glucose is easily transported
through an organism and the energy source for cellular respiration, the three monosaccharides
are six carbon sugars with the chemical formula C6H12O6. The human body stores energy in
the form of glycogen which is a highly branched polysaccharide this can be
broken down to transport energy to tissues. A disaccharide is the sugar which
is when two monosaccharides are joined by glyosidic linkage`s. Polysaccharides
are polymeric carbohydrate molecules composed of long chains of monosaccharide
units bound together by glyosidic linkages. They range in structure from linear
to highly branched. This could be the storage of polysaccharides such as starch
and glycogen, and structural polysaccharides such as cellulose and chitin.
Carbohydrates role within the cell membrane is to conduct the various type of
membrane mechanisms including facilitated diffusion and channel proteins
carbohydrates are not found separately within the membrane they are always
linked to a protein.

Enzymes are protein molecules that speed up chemical
reactions in the cell a special region in the enzyme called the active site is
the area where enzyme activity takes place an enzyme works by binding to
molecules to substrates at its active site the job of the enzyme is to convert
the substrate to a different product through a series of chemical reactions following
the reactions the products are released and the enzyme is free to react on
another substrate at the active site the substrate should fit into the enzyme
like a key that fits into a lock because of this most enzymes can only fit one
substrate to accomplish the lock and key fit the active site under goes a
slight change in shape in order to accommodate the substrate this is called the
induced fit model as the enzyme is induced to under go small changes so that
the substrate can achieve optimate fit all enzymes have optimal environmental
conditions that are correlated with maximum enzyme activity environmental
conditions such as PH and temperature play a role in how efficient the enzyme
is in conducting its reactions when conditions are less than optimal the enzyme
will lose its configuration and slow its activity this is due to a change in
the three dimensional shape of the enzyme and is known as denaturing.

The link
reaction will transport pyruvate into the mitochondria, aerobic respiration
uses available oxygen to oxidize the sugar molecule to produce greater ATP. Glycolysis
splits glucose into two pyruvate molecules, the link reaction occurs twice per
molecule of glucose

Cellular respiration can be broken down into three phases
the first is glycolysis which means the breaking down of glucose. This starts
with glucose C6H1206, the investment stage uses two
ATP`s then the glucose breaks up into two three carbon compounds which have a phosphate
group which occur from ATP. The Phosphoglyceraldehyde (PGAL) turns into pyruvate which is
another three carbons.

Living organisms obtain their energy through cellular
respiration these harvests electrons from carbon compounds and uses the energy
to make ATP. the Krebs cycle is a range of reactions involved in the aerobic
respiration process of cellular respiration for every turn of the Krebs cycle
one molecule of ATP and two molecules of carbon dioxide are produced two
electron carriers are used in this process the two-carbon compound acetyl co A
reacts with a four-carbon compound known as oxaloacetic acid to produce citric
acid which is a six-carbon molecule. A molecule of carbon dioxide is formed
reducing the product to a five-carbon compound in the process a molecule of NADH+
and H+ is produced another molecule of carbon dioxide is released forming a four-carbon
compound one molecule of ATP and a molecule of NADH are also produced the four-carbon
molecule passes through a series of reactions of FADH2 the H and H+ are formed. Finally,
acetyl co A and citric acid are generated and the cycle continues.

The electron transport chain produces the most ATP molecules. The chain is
a collection of proteins found on the inner membrane of mitochondria. NADH and
FADH2 release the electrons into the transport chain. Electrons
transfer energy to the proteins within the membrane which provides the energy
for hydrogen ions to be moved across the membrane. 

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