Question

1. Describe the function of lysosome in phagocytosis.

2. Write a chemical equation that describes one mechanism of drug detoxfication in the smooth ER.

Answer 1

Ans

1. Phagocytosis? is a greek word that means Phago= to devour, Cyto= Cell Osis = Process; Lysososme also greek word Lysis that means dissolution or destruction, and soma, means body.

Phagocytosis is the process by which engulfs a solid particle to form an internal compartment known as a phagosome and used to remove pathogens and cell debris. The pathogen becomes trapped in a phagosome which then fuses with a lysosome to form a phagolysosome, forming a phagolysosome and leading to degradation. In the phagolysosome, enzymes and toxic peroxides digest the bacteria, dead tissue cells and small mineral particles.

Phagolysosom leading to degradation can be oxygen dependent or oxygn independent

1. In oxygen-dependent degradation depends on NADPH and the production of ROS (reactive oxygen species). Hydrogen peroxide and myeloperoxidase activate a halogenating system, which leads to the creation of hypochlorite and the destruction of bacteria.

2. Oxygen-independent degradation depends on the release of granules, containing proteolytic enzymes such as lysozymes, and cationic proteins such as defensins. Other antimicrobial peptides are present in these granules, including lactoferrin, which sequesters iron to provide unfavourable growth conditions for bacteria.

Lysosome is a membrane-bounded organelle, found in the cytoplasm of eukaryotic cells, which contains acid hydrolytic (digestive) enzymes. It acts as the "garbage disposal" of the cell by breaking down cell components that are no longer needed as well as molecules or even bacteria that are ingested by the cell. They are found in animal cells, while in plant cells the same roles are performed by the vacuole.  

Lysosomes hydrolytic enzymes which are active at acidic pH including? Protease,? Nuclease,? Lipase,? Carbohydrase.

The lysosomes which does phagocytosis are known as ‘suicidal bags’

Another function of lysosomes is to dissolve the tail of frog known as Metamorphosis.

Ans 2. Drug detoxfication in the smooth ER: breackdown of harmful substances into the safe substances

Drug detoxificaation occurs primarly in the smooth ER of the liver cell due to the presence of large amounts of many varieties of enzymes. In liver drug toxification is known as hepatic metabolism while in other organs than liver like lungs, kidney, placenta, epithelial cells of gastrointestinal tract, adrenals and skin is called extrahepatic metabolism.

The cytochrome P450 (CYP) enzymes are also known as microsomal mixed function oxidases. The CYP enzymes are membrane-bound proteins, present in the smooth ER of liver and other tissues. They are the most important enzymes for Phase I biotransformation of drugs. These enzymes contain a heme prosthetic group, where heme group is the iron-porphyrin unit and oxidizing site, and is responsible for the oxidation of hydrophobic compounds to hydrophilic or more polar metabolites for subsequent excretion.

There are more than 300 different CYP enzymes, that grouped into several families and subfamilies based on the amino-acid sequence. Out of these, 18 CYP families have been identified in mammals, comprising majorly of families CYP1, CYP2 and CYP3.

CYP + Drug + O₂ + H⁺ + NADPH = Drug-OH (Oxidised drug) + H₂O + NADP⁺

Detoxification reaction occured in two phases, the phase I reactions are termed as nonsynthetic reactions including oxidation, reduction, hydrolysis, cyclization,and decyclization reactions. These reactions are carried out mostly by mixed function oxidases, usually involving CYP450 and occur in the liver. In these reactions, a polar group is either introduced or unmasked if already present. These reactions are succeeded by Phase II reactions. Most of the Phase I products are not eliminated directly; instead they undergo Phase II reactions.

Phase II reactions are the exactly drug detoxification pathways in that, a suitable moiety such as glucuronic acid, glutathione, sulphate, glycine, etc., get conjugated to the metabolites of Phase I reaction. These are also termed as conjugation reactions, because the metabolites are conjugated with the above-mentioned moieties which are large in size and strongly polar in nature. These reactions are catalyzed by a variety of transferase enzymes, such as uridine diphosphate (UDP)-glucoronsyltransferases, sulfotransferases, glutathione transferases. These transferases also exist as a superfamily of enzymes, similar to CYPs, but they differ in the number of drugs they metabolize.