1α-hydroxylase, converts 25-hydroxycholecalciferol to the active form, 1,25-dihydroxycholecalciferol.

TLS Online TPP Program

#Id: 8213

#Unit 2. Cellular Organization

Autophagy occurs in the following sequence of steps:

Induction by activation of mTOR complex 1

• Nucleation of autophagosome formation by ATG9

• Closure of the membrane cup to form autophagosome

• Fusion of the autophagosome with lysosomes, catalyzed by SNAREs.

• Digestion of the inner membrane and the lumenal contents of the autophagosome

TLS Online TPP Program

#Id: 8215

#Unit 2. Cellular Organization

Autophagy can be either

• Nonselective autophagy

• Selective autophagy

TLS Online TPP Program

#Id: 8216

#Unit 2. Cellular Organization

In nonselective autophagy, a bulk portion of cytoplasm is sequestered in autophagosomes

TLS Online TPP Program

#Id: 8217

#Unit 2. Cellular Organization

In selective autophagy

specific cargo is packaged into autophagosomes that tend to contain little cytosol, mediates the degradation of worn out, or unwanted, mitochondria, peroxisomes, ribosomes, and ER; used to destroy invading microbes.

TLS Online TPP Program

#Id: 8218

#Unit 2. Cellular Organization

Sorting signal that directs lysosomal hydrolases from the TGN to the late endosome is- Mannose 6-phosphate (M6P).

TLS Online TPP Program

#Id: 8219

#Unit 2. Cellular Organization

M6P residues are generated in the cis-Golgi by two Golgi-resident enzymes. 

1. N-acetylglucosamine (GlcNAc) phosphotransferase
2. Phosphodiesterase