Detection of apoptotic cells based on Aanexin- V binding

We are all know that , live cells have phospholipids asymetrically distributed in the inner and outer leaflet of plasma membrane, with most of phosphotidylserine on the inner leaflet. 

Early during apoptotic cells low asymmetry, exposing phosphotidylserine on the outer leaflet of plasma membrane.

Annexin-V is a calcium dependent phospholipid binding protein that binds preferentially to negative cahrged phosphatidylserine . Fluorphore conjugated Annexin-V is a useful reagent for the detection of apoptotic cells. 

Apoptotic cells can be detected on the basis of increased binding of FITC- conjugated Annexin-V.

Note= Annexin-V alone cannot distinguish cells dying by apoptosis from those dying by necrosis.

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Shubham Sharma

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ADH(antidiuretic hormone) effect on kidney function

Antidiuretic hormone(vasopressin) released by the posterior lobe of the pituitary plays a role in water reabsorption by the distal convoluted tubule and the collecting duct of the nephron.

ADH increase the water reabsorption. In practical term, if an individual does not drink much water on a certain day, the posterior lobe of the pituitary releases ADH, causing more water to be reabsorbed and less urine to form (antidiuresis).

On the other hand, if an individual drinks a large amount of water and does not prespire much, ADH is not released. In that case, more water is excreted and more urine forms( diuresis)

In this figure, ADH regulates the permeability of the late distal tubules and collecting ducts. ADH stimulates the synthesis of aquaporin- 2 and it's insertion into the membranes of the principal cells. ADH acts by binding to GPCR receptor on the plasma membrane. These receptor activate the enzyme adenylate cyclase through G protein which catalyses the synthesis of cAMP.

cAMP stimulates synthesis of aquaporin- 2 and insertion into the apical membrane by exocytosis.

NOTE= A deficiency in ADH secretion causes diabetes insipidus in which there is excessive urination ( polyuria) and excessive fluid intake( polydypsia)

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Shubham Sharma

Gmail- sspareek1998@gmail.com

In the translation, how activation of amino acid and attachment of tRNA?

Attachment of amino acid to tRNA involves a covalent linkage between the carboxyl group of the amino acid and the 2' or 3' hydroxyl group of the adenine containing nucleotide at the 3' end of the tRNA. 

Above this process is catalyzed by an enzyme called aninoacyl- tRNA synthetase

Aminoacyl-tRNA synthetase activates the amino acid by covalent linking it to tRNA. When a tRNA is charged with the amino acid corresponding to its anticodon, it's called aminoacyl tRNA.

Aminoacylation reaction= The aminoacylation reaction is performed by two steps in which amino acid is first activated by ATP, forming an intermediate aminoacyl adenylate, and the second step the amino acid is transferred to the 3' end of the tRNA.

Source: pathfinder book 

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