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#lysosomes

9 public questions tagged with this topic.

Membrane Transportation

Which ATPase is involved in pH regulation in lysosomes and vacuoles?

V-class ATPases also called V-type vacuolar H+-ATPases are large multi-subunit rotary pumps related to F-type ATP synthases but functioning as ATP-driven proton pumps rather than ATP synthetic machines. Complex comprises peripheral V1 sector containing eight subunits including A3B3 hexamer that hydrolyzes ATP and membrane integral Vo sector with proteolipid c-ring, subunit a and accessory subunits mediating proton translocation. Hydrolysis-driven rotation of central stalk couples to c-ring rotation within Vo pumping H+ into lumen. In cells V-ATPase localizes to lysosomes, endosomes, vacuoles,

Ref: Forgac, Nat Rev Mol Cell Biol 2007, Vacuolar H+-ATPases; Alberts, 7th ed., Chapter 13 acidification.

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Membrane Transportation

Which ATP pump is involved in generating acidic pH inside organelles like lysosomes?

Generating acidic interior in endocytic compartments essential for cargo sorting, iron release from transferrin, ligand receptor dissociation, viral entry and lysosomal hydrolysis demands active proton translocation against roughly two pH units. Main machinery responsible is vacuolar proton ATPase V-type, large composite enzyme about 900 kilodaltons composed of peripheral V1 complex A3B3CDE3FG3H where A3B3 hexamer contains catalytic ATP hydrolysis sites at alternating interfaces, and integral membrane Vo complex including a subunit with two half channels, c-ring of nine to ten copies c, c doub

Ref: Forgac, V-ATPase Review, Acidification of Lysosomes and Endosomes by V-Class Proton Pump.

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Cell Organelles

The hydrolytic enzymes of lysosomes function best at pH:

Lysosomal acid hydrolases number about sixty different enzymes covering proteolysis, glycoside cleavage, lipid hydrolysis, nuclease activity and sulfatase action, each evolutionarily tuned for acidic environments to maximize substrate turnover and simultaneously protect cell from uncontrolled proteolysis if leakage occurs. Most display pronounced pH optima between 4.5 and 5.0, precisely matching steady-state lumen acidity maintained by vacuolar H+ ATPase delivering protons and chloride counter-transport via ClC-7 Cl-/H+ antiporter that prevents excessive voltage buildup. At this acidic pH cata

Ref: Alberts et al., Molecular Biology of the Cell, 6th ed., Chapter 13: Lysosomal Acid Hydrolases – pH Optimum 4.5.

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Cell Organelles

Late endosomes fuse with:

Endosomal maturation transforms early sorting compartments into degradative organelles preparing cargo for destruction and nutrient recovery. Late endosomes, also termed multivesicular bodies, marked by switch from Rab5 to Rab7 GTPase, more acidic pH near 5.0 to 5.5 due to increased V-ATPase density, and accumulation of intraluminal vesicles formed by ESCRT machinery, move toward microtubule organizing center along microtubules via RILP and dynein. They progressively acquire lysosomal membrane proteins LAMP1, LAMP2 and soluble hydrolases via transport from trans-Golgi network through mannose-6

Ref: Huotari & Helenius, EMBO Journal, 2011: Endosome Maturation and Fusion with Lysosomes.

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Cell Organelles

Lysosomes are derived from:

Lysosomal enzymes traverse secretory pathway originating from rough ER translocation, folding and initial N-glycosylation, then Golgi where specific modification marks them for diversion from default secretion. Cis-Golgi N-acetylglucosamine phosphotransferase recognizes lysine-containing conformational patch present only on soluble hydrolases, transferring GlcNAc-one-phosphate onto terminal mannose residues of high mannose oligosaccharides, forming phosphodiester. Uncovering enzyme in trans-Golgi removes GlcNAc leaving mannose-six-phosphate monoester. Trans-Golgi network clathrin adaptors AP1

Ref: Kornfeld Annu Rev Biochem; Golgi M6P pathway GlcNAc phosphotransferase tags lysosomal hydrolases.

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Endomembrane System - ER Golgi Lysosome Vacuole

Organelle P is a membrane-bound vesicle containing hydrolytic enzymes that function best at acidic pH. Organelle Q is do

Lysosomes are membrane-bound vesicles containing hydrolytic enzymes that are optimally active at acidic pH. Mitochondria are double-membrane organelles whose inner membrane forms cristae and whose aerobic respiratory activity generates ATP.

Ref: NCERT Class 11 Biology Chapter 8: Cell: The Unit of Life Endomembrane System - ER Golgi Lysosome Vacuole

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Protein

The primary function of lysosomal protein degradation is:

Non-specific degradation of intracellular components is the accurate answer because it correctly identifies the biological function or role described in this question. In Protein Degradation, understanding the specific functions of molecules, enzymes, or structures is fundamental. Non-specific degradation of intracellular components fulfills this particular biological role through its specific structural properties, biochemical activity, or physiological mechanism. The other options (Energy production, Regulation of metabolic pathways, and ATP-dependent selective degradation) serve different b

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4

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