Download cell signalling

Cell surface Membrane
Receptors, Communication
and cell signalling
Objectives
To know the role of receptors in
cell signalling
Why the need for receptors?
• Cells need to be able to sense and
respond to changes in their internal
and external environment
• cells need to communicate
information between each other by
the process of cell signalling
What is Cell signalling?
• Cell signalling controls basic cell
activities and coordinates cell actions
• E.g. cytokines produced by the cells of
the immune system indicate to the body
the presence of a pathogen
What are receptors?
Receptors are proteins and modified
proteins (such as lipoproteins and
glycoproteins) on the cell surface
membrane (part of the glycocalyx) that
respond to a specific signal and have a
complementary shape to the signal
molecule.
Examples of receptors
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Hormone receptors
Drug receptors
Neural receptors
Self recognition receptors
Growth regulator receptors
Antigenic receptors
Hormone receptors
• Hormones are chemical messengers
secreted into the blood by a gland and
transported to a target tissue
• The hormone identifies a target cell by
its complementary cell surface receptor
• By binding to the receptor the hormone
initiates a cascade (series) of events
(chemical reactions) inside the cell
Hormone Receptors
Insulin as an example
• Insulin (a protein hormone) is secreted by
the beta cells of the Islets of Langerhans
in the pancreas in response to raised
blood glucose levels
• It binds to the insulin receptor on muscle
and liver cells increasing the uptake of
glucose from the blood into the cells
decreasing blood glucose levels
Insulin receptors
Medicinal Drugs
Scientists have formulated chemicals with
a complementary structure to a specific
receptor and can be used to bind and block
the natural pathway the receptor is
involved in E.g. beta blockers regulate
heart rate
Viruses and cell surface
receptors
HIV virus has a complimentary shape to a
receptor on lymphocyte cells (white blood
cells), binding allows it to enter the cell
where it then reproduces and destroys
the cell.
Metabolic poisons
• Nicotine binds to receptors on the post
synaptic membrane of nerves and acts
as a stimulant by opening the channels
• Curare (arrow poison) binds to the same
receptors blocking them causing
paralysis
• Clostridium botulinum toxin also causes
paralysis of muscle fibres by binding
with receptors. The lethal toxin is now
used as BOTOX.
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