Communication between Cells

Understanding Inter Cell Communication
Communication between cells is the interaction between one cell and another cell or between cells and their environment.
The purpose of this communication is so that every organ in our body can carry out its functions properly so as to maintain survival.
Humans can get information because they communicate with other people. Human communication is done by using various media such as sound, images or body movements.

Sounds, images or body movements are examples of information.
Information can come in various forms. In fact, there is also information whose shape changes from one form to another.
When we call for example. Our sound waves are converted into electrical signals so that they can flow through telephone cables. An important point of this process is when the message is changed from one form to another. This change process is called signal transduction.


Also Read :  Plant Cells and Organelles and Their Functions

So how can intercellular communication occur? What use? The answer can be found in the explanation below.

Signal Molecules (Ligands)

Plant cells and animal cells communicate using extracellular signal molecules called ligands. This communication aims to control cell metabolism, growth, tissue differentiation, protein synthesis and protein secretion and regulate the composition of extracellular fluid.

This signal molecule or ligand is synthesized (made) and secreted by the signal cell. One signal molecule only produces one specific response in the target cell that has a specific receptor (according to response).

In multicellular organisms, signal molecules can be hydrophilic or hydrophobic molecules. Both groups of molecules have different mechanisms in the process of working in cells.

Some hydrofibic signaling molecules such as steroids, retinoids and thyroxine can function both within cells and bind to intracellular receptors (between cells). There are 2 types of intracellular receptors, namely receptors found in the cytoplasm (Cytoplasmic Receptor) and in the cell nucleus (Nuclear Receptor).

Various hydrophilic small molecules such as (amino acids, lipids, and acetylcholine), peptides and proteins are used for cell-to-cell communication.

Signal molecules are steroid hormones (estradiol, progesterone, testosterone), vitamin D 3 and retinoic acid which can penetrate cell membranes and bind to intracellular specific receptors and form hormone receptor complexes.

Then it translocates into the cell nucleus and binds to DNA elements that are responsive to complex receptors. This process causes the activation of the target gene to synthesize certain proteins.

The way of communication between other cells is through receptors found on the surface of cell membranes (membrane receptors). In this case the ligand molecule works as a ligand that binds to complement molecules on the outer surface of the cell membrane.

This bond causes changes in the receptor component in the cell or induces a specific cellular response. This process is known as signal transduction.

One group of receptors on the membrane surface that activates protein G is known as G proteincoupled receptors (GPCRs). GPCRs are found in all eukaryotic cells, from yeast (yeast / fungus) to humans.


Humans can code several thousand GCPR. This includes receptors in the eye, touchers, flavorings, some neurotransmitter receptors and hormone receptors that control the metabolism of carbohydrates and amino acids in general.

Molecules of Signals and Receptors of Membrane

Communication using extracellular signals usually involves the following steps:

1. Synthesis
2. Release of signal molecules by signal cells 
3. Transport the signal to the target cell 
4. The signal molecule binds to the receptor protein to activate it 
5. Initiation of one or more transduction signal pathways that have been activated by receptors 
6. Specific changes in cellular function, metabolism or development and 
7. Signal release so that often causes the cellular response to cease.

Most receptors are activated by bonding molecules with membranes (eg hormones, growth factors, neurotransmitters and pheromones). There are several ways of cell communication that use membrane receptors namely juktacrin, autocrine, paracrine and endocrine.

Signaling juktakrin

Juktakrin signaling is the communication of two cells adjacent to forming a pore that connects the two cells so that the smallest ions and molecules can pass through the pores that form.

Autocrine signaling

Signaling cell autocrine or cells responds to molecules that are secreted by themselves. This signal is also found in tumor cells that are over-secreted by growth factors to induce uncontrolled cell proliferation. This causes the formation of tumors that can suppress the surrounding tissues or organs.

Paracrine sign

Paracrine signaling is a short distance communication between cells. The signal cell secretes its target signal molecule in cells adjacent to the signal cell.

For example epinephrine is a neutotransmitter released by one nerve cell to another nerve cell or nerve cell to effector in skeletal muscle (stimulates or inhibits contraction). Then it can bind to membrane receptors in the surrounding target cells and induce changes in the target cell.

Endocrine Signaling

Endocrine signaling is an example of communication between long-distance cells because the signal cell is located in a location that is relatively far from the target cell. In this signal the signal molecule is a hormone. The signal molecule can get to the target cell because it is transforced through blood or other extracellular fluid.

Endocrine signaling, for example, occurs in the female reproductive cycle. The hormones involved can be either peptides or steroids. Peptide hormones such as follicle stimulating hormone (FSH), Lutenizing Hormone (LH) and Gonadotropins. While steroid hormones such as estrogen and progesterone.
Endocrine signaling mechanism in the female reproductive cycle

Intraselular Transduction Signals

Transduction signals are the process of converting a signal molecular bond to the target cell receptor to produce a biological response. In this case there are second messengers that work as signal transduction agents. This second messenger can carry signals from several receptors.

In signal transduction of bonds with ligands (first messenger) on several membrane receptors in a short time can increase or decrease the concentration of small molecules which are second messengers. Some of the following molecules are cAMP (cyclic AMP), cGMP, DAG (1,2 diacylglycerol) and inositol triphosphate (IP3) which act as Second messenger.
PROTEIN G (GPCR) RECEPTOR COMMITMENT THAT ACTIVATES OR LIMITS ADENIL CYCASE

There are numerous membrane receptors associated with G protein transduction signals. All GPCR consists of seven segments where terminal N is outside the membrane and terminal C is contained in the cytosol.