Cell communication. Premedical B iology. The plasma membrane. is fluid mosaics of lipids and proteins, it consists of double layer of phospholipids and other lipids with attached proteins. controls traffic into and out of the cell it surrounds
Phospholipids are amphipatic molecules
Proteins are embeded or attached to surface.
determine many of the membrane‘s specific functions
Integral proteins – transmembrane proteins
Peripheral proteins – are not embeded in the lipid bilayer
Active transport is the pumping of solutes against concentration gradients „uphill“
It is the major mechanism of ability of cell to maintain internal concentrations of small molecules that differ from concentrations in environment.
Direct contact between membranes by cell-surface molecules
= cell junctions = intracellular joining
= cell-cell recognition (glycolipids and glycoproteins)
Cell walls of plant cells perforated with channels called plasmodesma.
In animals are intracellular junctions.
also by carbohydrates(linked to proteins and lipids), which
helps to sort cell into tissues and organs in embryo and
helps to recognize and reject the foreign cells in the immune system
Carbohydrates are usually short branched oligosaccharides.
Plant cells (some Protists, prokaryotes, fungi) encased
by cell walls
Animal extracellular matrix – ECM with
Collagen fibers are embedded in network of proteoglycans.
Fibronectins bind to receptor
protein called integrins in plasma
membrane. Integrins bind to
microfilaments (cytoskeletal pr.)
on cytoplasmatic side.
Cell responds to external signals.
A signaling molecule (ligand/first messenger) binds to a receptor protein in membrane and causes a change of his shape (enzyme). On internal side is the signal transformed in the cascade of molecular interactions with origin of second messengers. In nucleus signal leads to regulation of transcription or other cytoplasmatic activities.
Signaling molecule + Receptor
Receptor or protein associated with get activated and it is able to transfer the signal inside the cell.
G protein coupled receptors / inhibitory or activity
Receptor tyrosine kinases have enzymatic activity and catalyze transfer of phosphate groups
Ion channel receptors withgate open or close
Multistep pathway (cascade) of activation of proteins by addition or removal of phosphate groups or it starts by the origin of small molecules or ions that act as seconder messengers.
Phosphorylation and dephosphorylation of proteins acts as a molecular switch.
Protein kinases transfer phosphate groups from ATP to protein.
Multiple steps of signal transduction greatlyamplify the signal. In each step the number of activated products is much greater than one step before.
Multiple steps also provide different points, at which the response can be regulated and also provide a specifity of cell signaling and coordination.
Nonprotein molecule, which can be spreaded by diffusion – cAMP and
Protein are sensitive to
the cytosolic concentration
of one or other.
Neurotransmitters, growth factors, hormones induce cell’s responses via signal transduction pathways that increase the concentration of calcium ions.
Responses: muscle contraction, secretion of substances, cell division
Second messengers: inositol triphosphate and diacylglycerol
The end of pathway may occur in the nucleus or in the cytoplasm = the change of transcription or cytoplasmic activities.
Response in nucleus is the regulation the activity and synthesis - transcription factors
Campbell, Neil A., Reece, Jane B., Cain Michael L., Jackson, Robert B., Minorsky, Peter V., Biology, Benjamin-Cummings Publishing Company, 1996 –2010.