bio signaling ppt

2. Earl W. Sutherland, Nobel Address, 1971
When I first entered the study of hormone
action, some 25 years ago, there was a
widespread feeling among biologists that
hormone action could not be studied
meaningfully in the absence of organized cell
structure. However, as I reflected on the history
of biochemistry, it seemed to me there was a
real possibility that hormones might act at the
molecular level.

3.  Signal transduction (also known as
Biosignaling/ cell signaling)
 Signal transduction is the transmission of
molecular signals from a cell's exterior to its
interior.
 Signals received by cells must be transmitted
effectively into the cell to ensure an
appropriate response.
 Signaling receiving is initiated by cell-surface
receptors.
 Signal transduction, is a universal property of
living cells.

4.  Bacterial cells receive constant signals from
membrane proteins.
 That act as information receptors, sampling the
surrounding medium for pH, osmotic strength, the
availability of food, oxygen, light, the presence of
noxious chemicals and predators etc.
 Animal cells exchange information about the
concentrations of ions and glucose in extracellular
fluids, the interdependent metabolic activities in
tissues, and, in an embryo, the correct placement of
cells during development.

5.  Transmission is continued either by a series of
biochemical changes within the cell
 OR by modification of the cell membrane
potential by the movement of ions in or out of
the cell.
 Receptors that initiate biochemical changes can
do so either directly via intrinsic enzymatic
activities within the receptor or by activating
intracellular messenger molecules.

6.  Signal transuding receptors are of four general
classes.
 Ion Channel–Linked Receptors
 G Protein–Linked Receptors
 Enzyme-Linked Receptors
 Nuclear Receptors

7.  Virtually all the neurotransmitter substances,
such as acetylcholine and
norepinephrine,combine with receptors in the
postsynaptic membrane.
 This almost always causes a change in the
structure of the receptor, usually opening or
closing a channel for one or more ions.
 Ion channel–linked receptors open (or close)
channels for sodium ions, others for potassium
ions, others for calcium ions, and so forth.

9.  G protein is group of protein.
 Loosely attached to inner membrane.
 Acts like on-off switch.
 Inactive form when bound to GDP.
 Active form when bound to GTP.
 G-protein soon breaks GTP down to GDP, so
"on" state switches back to "off".
 Target usually a membrane-bound enzyme.
 Enzyme is inactive until activated by active G-
protein.

11.  Enzyme-linked receptors have an extracellular
ligand-binding domain linked to an
intracellular domain that possesses an intrinsic
catalytic activity.
 When the ligand binds to the extracellular part
of the receptor, an enzyme immediately inside
the cell membrane is activated .
 One example of an enzyme-linked receptor is
the leptin receptor .

12.  Leptin is a hormone secreted by fat cells and
has many physiological effects especially
important in regulating appetite and energy
balance.
 The leptin receptor exists as a dimer
 Binding of leptin to the extracellular part of the
receptor alters its conformation, enabling
phosphorylation and activation of the
intracellular associated JAK2 molecules.

13.  JAK2 complex to mediate intracellular
signaling.
 The intracellular signals include
phosphorylation of signal transducer and
activator of transcription (STAT) proteins.
 STAT protein activates transcription by leptin
target genes to initiate protein synthesis.
 Phosphorylation of JAK2 also leads to
activation of other intracellular enzyme
pathways

14. IRS Insulin receptor substrate
STAT signal transducer and activator of transcription
JAK2 Janus kinase 2 Enzyme

15.  Nuclear receptors are signaling transduction
receptor that are activated by lipid-soluble
signals inside the cell.
 Unlike most intercellular messengers, the
ligands can cross the plasma membrane and
directly interact with nuclear receptors inside
the cell.
 Once activated, nuclear receptors directly
regulate transcription of genes .

16.  Although nuclear receptors primarily function
as transcription factors but also control a wide
variety of biological processes, including cell
proliferation, development, metabolism, and
reproduction.
 Some have also been found to regulate cellular
functions within the cytoplasm.

18.  The most important functions of cell signaling
is to control and maintain normal physiological
balance within the body.
 Activation of different signaling pathways
leads to diverse physiological responses, such
as cell proliferation, death, differentiation, and
metabolism.

19.  In a healthy organism, the processes of cellular
growth and differentiation are tightly
controlled
 In the pathological state, damage-causing
signals, or the growth of the malfunctioning
cells.
 Proliferation of damaged or malfunctioning
cells is often a key factor in the generation of
disorders

20.  The most come disorder of bio signaling
Include , cancer, infectious diseases,
inflammation, arteriosclerosis, arthritis,
and neurodegenerative diseases.