All types of stimuli that trigger certain responses from cells are broadly classified into two categories:
Self/ Endogenous Ligands
A ligand is a carrier molecule that can binds to a stimulus, thus, producing a signaling molecule. Ligands bind to specific receptors in or the surface of the cell.
Self/endogenous signals are signaling molecules produced by the body itself. They are part of normal cellular communication.
2. Non-self/Exogenous Ligands:
These are signals produced by a foreign source such as a pathogen or a drug administered into the body. Basically, any signal that is foreign to the body and not produced by the body itself are exogenous ligands. Exogenous ligands elicit an immune or allergic response in the body. When identified, these ligands and their source is attacked by the immune system.
Answer: 1 : knowledge about the natural world that is based on facts learned through experiments and observation. 2 : an area of study that deals with the natural world (as biology or physics)
When stating a routine request up front, what you should do
is as you have your request told, you should assume that the audience present
in the situation will be able to comply with the routine request that you have
asked or suggested.
The main advantage of monomers or basic subunits of macromolecules is their simplicity. The simple monomeric subunits from which all proteinsnucleic acids, fats and carbohydratesare constructed are few in number and identical in all living species.These simple monomerc units can be linked in many different combinations (different covalent bonds) to produce complex biological polymers with different functions.
