Showing posts with label Dictionary. Show all posts
Showing posts with label Dictionary. Show all posts

Friday, July 3, 2020

What is ergosterol

/ by  / in / with No comments /

Ergosterol occurs in plants. it is also found as a structural constituent of membranes in yeast and fungi.

Ergosterol in an important precursor for vitamin D.
yeast-constituents-fungi-constituents-vitamin-D
Structure of Ergosterol
When exposed to light the ring B of ergosterol opens and it is converted to ergocalciferol, a compound containing vitamin D  activity.

Organ transplantation

/ by  / in , / with No comments /

The phenomenon of transfer of cells, tissues or organs from one site to another (in the same organism, autograft or from an organism allograft) is regarded as organ transplantation.

In case of humans, majority of organ transplantations are allograft (between two individuals). the term xenograft is used if tissue or organ are transferred from one species to another for example - from pig to man.

Organ transplantation is associated with immunological complications, and tissue rejection. this is because the host body responds to the transplanted tissue in a similar way as if it were an invading foreign organism.

Major histocompatibility complex (MHC) is primarily involved in allograft rejection. this is due to the fact that MHC proteins are unique to each individual and the immune system responds promptly to foreign MHCs.

Organ transplantation between closely related family members is preferred, since their MHCs are also likely to be closed related. and major immunological complications can be averted.   

what is autoimmune diseases

/ by  / in / with No comments /

Immune system is self-tolerant i.e. not responsive to cells or proteins of self.

sometimes, for various reason, the immune system fails to discriminate between self and non-self. As a consequence, the cells or tissues of the body are attacked. this phenomenon is referred as autoimmunity and the diseases are regarded as autoimmune diseases.

The antibodies produced to self molecules are regarded as autoantibodies. 

what is Adsorption

/ by  / in / with No comments /

Adsorption is a surface phenomenon. it is the process of accumulation of a substance (adsorbate) on the surface of another substance (assorbent).

Adsorption differ from absorption, as the latter involves the diffusion into the interior of the material.

The capacity of an adsorption depends on the surface area.

therefore, porous substances serve as better adsorption for example - charcoal, alumina, silicagel.

Adsorption is a dynamic and reversible process which decreases with rise in temperature.   

what is isotopes

/ by  / in / with No comments /

Isotopes have revolutionized biochemistry when they became available to investigators soon after second world war.

Isotopes are defined as the elements with same atomic number but different atomic weight.
they possess the same number of protons but differ in the neutrons in their nuclei.

Isotopes - iso means equal and tope means place.

Isotopes occupy the same place in the periodic table.

the chemical properties of different isotopes of a particular element are identical.

what is Sodium-potassium pump

/ by  / in / with No comments /

The cells have a high intracellular  K+ concentration and a low Na+ concentration. this is essentially needed for the survival of the cell. 

high cellular K+ is required for the optimal glycolysis and for protein biosynthesis. further, Na+ and K+ gradients across plasma membranes are needed for the transmission of nerve impulse.  

Na+

Difference between prokaryotic and eukaryotic cell

/ by  / in , / with No comments /

S.No.
Characteristic
Prokaryotic cell
Eukaryotic cell
        1)       
Size
Small (generally 1-10µm)
Large (generally 10-100µm)
        2)       
Cell membrane
Cell is enveloped by a rigid cell wall
Cell is enveloped by a flexible plasma membrane
         

       3)       
Sub-cellular organelles
Absent
Distinct organelles are found ( Examples – mitochondria, nucleus, lysosomes, ribosomes, endoplasmic reticulum)
      
        4)       
Nucleus
Not well defined; DNA is found as nucleoid, histones are absent  
Nucleus is well defined, surrounded by a membrane; DNA is associated with histones

        5)       
Energy metabolism
Mitochondria absent, enzymes of energy metabolism bound to membrane
Enzymes of energy metabolism are located in mitochondria
         6)       
Cell division
Usually fission and no mitosis
Mitosis

         7)       
Cytoplasm
Organelles and cytoskeleton absent
Contains organelles and cytoskeleton (a network of tubules and filaments)

what is apoptosis

/ by  / in / with No comments /

Apoptosis is the programmed cell death or cell suicide. this occurs when the cell has fulfilled its biological function. apoptosis may be regarded as a natural cell death and it differs from the cell death caused by injury due to radiation, anoxia etc.

Programmed cell death is highly regulated process.

What is peroxisomes

/ by  / in / with No comments /

Peroxisomes, also known as microbodies, are single membrane cellular organelles. they are spherical or oval in shape and contain the enzyme catalase.

Catalase protects the cell from the toxic effects of hyderogen peroxide by converting it to and Peroxisomes are also involved in the oxidation of long chain fatty acids and synthesis of plasmalogens and glycolipids.

Plants contain glyoxysomes, a specialized type of peroxisomes, which are involved in the glyoxylate pathway. 
Subscribe to: Comments (Atom)