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Definitions:Cytoplasm – the material or protoplasm within a living cell, excluding the
nucleus
Mitochondria – an organelle found in large numbers in most cells, in which the
biochemical processes of cellular respiration and energy production take place
...
Involved in secretion and intracellular
transport
Endoplasmic Reticulum – a network of membranous tubules within the
cytoplasm of a eukaryotic cell, continuous with the nuclear membrane
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This
receptor is activated by the binding of a
molecule known as the first messenger
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This is mostly in the form
of a change in the regulation and expression of
certain genes
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Note that the receptors can commonly
transmembrane receptors
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Note that some first messengers actually enter the
cytoplasm physically
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Tyrosine
kinases are commonly found with transmembrane receptors
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A phosphate group is removed from the ATP and attached to
the target protein
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The protein must have a
specific amino acid (e
...
tyrosine in the case of tyrosine kinases) and a very
specific set of amino acids surrounding that single amino acid
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In other words, kinases have incredible specificity
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This process is critical in embryonic development as
it leads to specialization of cells
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DNA Helicase unwinds and separates a portion of DNA
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The enzyme complex DNA polymerase engages the single strand and initiates
the process of replication
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Therefore, replication begins
as the enzyme primase assembles an RNA primer at the start of replication
site
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DNA
polymerase adds DNA nucleotides to the RNA primer
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DNA is bidirectional 5’ – 3’ and 3’ – 5’
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It can only move in this direction
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Each fragment requires a separate RNA primer
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The fragments are then bonded together as a
continuous strand
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It is the
flow of information from DNA to protein
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All cells, from
bacteria to human, express their genetic information in this way
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RNA is quite similar to DNA but has a number of
crucial differences:
1
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RNA contains the base Uracil (U) in place of Thymine (T) as found in DNA
3
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Allows for folding into complex, 3-D structures
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Some folded RNA molecules have catalytic effects
The enzymes that catalyse transcription are the family of RNA polymerases
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RNA polymerase moves stepwise along the DNA, unwinding the
DNA helix just ahead of the active site for polymerisation to expose a new
region of the template strand for complimentary base pairing
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i
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RNA polymerase copies the DNA from 3’ to 5’
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There is a
whole complex of other proteins, called transcription factors
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These
proteins are often targets of signalling cascades
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When RNA polymerase molecules follow hard on each other heel’s
in this way, each moving at about 20 nucleotides per second (the speed in
eukaryotes), over a thousand transcripts can be synthesised in an hour from a
single gene
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This is because RNA polymerase does not need to be
as accurate as DNA polymerase – RNA does not store the genetic material
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There are many different types of transcription factors
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Chromatin and histones are also considered to be transcription factors
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Effects on DNA binding
2
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The final result is the stimulation or inhibition of transcriptional activity of a
particular factor
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Each disease has specific
characteristics – symptoms, course of development and changes in bodily
function
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Cause of disease can be endogenous or exogenous
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g
...
g
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e
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A
good example of this is diabetes mellitus type II
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g
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Diseases caused by medical treatment are called iatrogenic e
...
anaemia
caused by cytotoxic drugs used to treat cancer (chemotherapy)
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g
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This is known as a risk factor – something
which increases the likelihood of a disease occurring
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Clinical manifestations of disease include signs and symptoms
Symptom is feature of disease that patient complains about –for example pain
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Disease can involve different types of abnormalities such as altered secretion
of hormones -for example too low or too high concentration of glucocorticoid
hormones can lead to Addison disease or Cushing syndrome
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Cushing
syndrome manifest as facial hair, obesity, hypertension etc
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Prognosis is a prediction of the outcome of a disease
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Relapse is the return of a disease after a remission
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