1) The document discusses various methods of transporting biomolecules within and across cell membranes, including active transport which requires energy, and passive transport methods like diffusion, osmosis, and facilitated diffusion. 2) It also describes different types of cell receptors - extracellular receptors which span cell membranes and intracellular receptors located within cells. Examples like G-protein receptors, tyrosine kinase receptors, integrins, toll-like receptors, and nuclear receptors are provided. 3) The role of second messengers like calcium and cyclic GMP in signal transduction pathways is explained, where first messengers like hormones bind to cell surface receptors and trigger second messengers that diffuse within the cell to produce responses.

1. GKVK,BANGLORE
PRESENTED BY-UDIT NANDAN MISHRA
Jr. M.Sc. PLANT BIOCHEMISTRY
ID-[PALB-4230]5/31/2018 1

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3. Introduction-
Cells have many methods to transport biomolecules (either solutes
or may be signals) within & across the membrane barrier by
methods called translocation & in later case it is transduction for
perceiving a particular signal for doing an action in a targeted organ.
For translocation different methods enlisted are:-
a) ACTIVE METHOD.(expenditure of energy)
b) PASSIVE METHODS.(without spending energy)
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4.  Energy needs to be
spend in form of ATP.
 Against the
concentration
gradient(low to high).
 Eg : Cells have high
concentration of “K” &
low concentration of “Na”
inside but “Na” will move
out against concentration
gradient in order to
neutralize the “K” conc.
 process called
sodium-potassium pump.
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5. PASSIVE METHODS
are classified further-
 diffusion.
 osmosis.
 facilitated
diffusion.
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6. -
-
-
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10.  For a coordinated function of cells in a tissue, tissues in an
organ, organs in a system and systems in the body, cells need
to be able to communicate with each other.
 Each cell should be capable of sending chemical signals to
other cells and of receiving chemical signals from other cells,
as well as signals (chemical or other) from its immediate
environment.
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12. It is a way for a cell to alter its own extracellular environment, which in turn affects
the way the cell functions. The cell secretes chemicals outside of its membrane and
the presence of those chemicals on the outside modifies the behavior of that
This process is important for
It is a way for a cell to affect the behavior of by secreting
chemicals into the common intercellular space. This is an important process during
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13. . An example of this process can be found in the heart. The muscle cells in
the heart communicate with each other via gap junctions which allows all heart
cells to contract almost simultaneously
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14. Synaptic signaling
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16. What is signal transduction ?
A set of chemical reactions in a cell
that occurs when a molecule, such as
a hormone, attaches to a receptor on
the cell membrane. The pathway is
actually a cascade of
biochemical reactions inside
the cell that eventually reach the
target molecule or reaction.
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19. WHAT IS A RECEPTOR ????
 to which ligand molecules binds for further steps to carry out.
They are of following types-
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20. EXTRACELLULAR RECEPTORS
 Extracellular receptors are integral
transmembrane proteins and make up
most receptors .They are having with
one part of the receptor on the outside
of the cell and the other on the inside.
 Signal transduction occurs as a result of
a ligand binding to the outside; the
molecule does not pass through the
membrane
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21.  This binding stimulates a series of
events inside the cell; different types
of receptors stimulate different
responses and
 Upon binding, the ligand induces a
change in the conformation of the
inside part of the receptor.
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22. Some examples of extracellular receptors are given
below-
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24. G-protein receptors…
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26. Tyrosine
kinase
receptors
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28. Integrin-
Ligands for integrin include fibronectin , vitronectin , collagen,
and laminin. when these ligands bind to receptors a channel will be
created and the impermeable effector molecule will pass through this
channel to the targeted cell.
• Histidine kinase receptors normally found in prokaryotes, fungi
& plants.
• Here first the histidine is phosphorylated by ATP histidine kinase and
then shifts to aspartate there by phosphorylating it.
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29. -Toll-like receptors (TLRs) are a class of
proteins that play a key role in the
.
-They are single, membrane-spanning,
non-catalytic receptors usually
expressed in macrophages and
dendritic cells, that recognize
structurally conserved molecules
derived from microbes.
-eg : TLR1,TLR2,TLR3 etc.
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30. o Intracellular receptors, such as
and are soluble proteins
localized within their respective areas.
oThe typical ligands for nuclear receptors are lipophilic hormones like
the steroid hormones, testosterone and progesterone and derivatives of
vitamins A and D.
oTo initiate signal transduction,
.
o On binding with the receptor, the ligands pass through the nuclear
membrane into the nucleus, enabling
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31. Activated nuclear receptors attach to the DNA at
receptor-specific hormone-responsive
element (HRE) sequences, located in
the region of the genes activated by the
hormone-receptor complex.
Due to their enabling gene transcription,
they are alternatively called inductors
of gene expression.
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32. • First messengers are the intercellular chemical messengers (hormones,
neurotransmitters, and paracrine/ autocrine agents) that reach the cell
from the extracellular fluid and bind to their specific receptors.
• Second messengers are the substances that enter the cytoplasm and act
within the cell to trigger a response. In essence, second messengers serve
as chemical relays from the plasma membrane to the cytoplasm, thus
•
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34. Calcium as a secondary
messenger
Helps in Physiological roles
viz.
-Muscle contraction
-Neuronal transmission
-Cellular motility
-Fertilization
-Cell growth proliferation
-Secretion of saliva5/31/2018 34

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37. acts as a second messenger because it is a free
radicles that can diffuse through the plasma membrane and affect
nearby cells.
It is synthesized from arginine and oxygen by the and
works through activation of , which when
activated produces another second messenger, cGMP.
It is and causes damage during
but is the cause of many other functions
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39. Conclusion-
Signal transduction & translocation is all about how a
particular work or perception is received by a target organ
after getting a message from neighbouring as well as distant
signal generating organs.
This also shows a regulated path by which various receptors
are engaged in transferring the required message to the
targeted organ and cell.
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40. References-
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I. Paswon,T.1995.protein modules and signaling networks
. Nature 373:573-580
II. Lambright, D.G., Noel , J.P., Hamm , H.E., and Sigler ,
P.B. 2004.Structural determinants for activation of alpha
subunit of heteromeric G protein. Nature 369:621-628
III. Biel, M., 2009. Cyclic nucleotide-regulated cation
channels. The journal of Biological chemistry 284:9017-
9021
IV. Biochemistry by Donald Voet & Herpus illustrated
Biochemistry