Where are phospholipids and sphingolipids degraded in the cell?
Complex lipids such as glycerolipids and sphingolipids as well as proteins have to be degraded within the process of endosomal/lysosomal membrane digestion, so that the final degradation products can leave the compartment.
Are sphingolipids the same as phospholipids?
Sphingolipids are membrane lipids with a structure similar to phospholipids: a backbone containing two fatty acids and a head group. However, the backbone is serine instead of glycerol.
How are sphingolipids degraded?
They are degraded in lysosomes by a defined sequence of enzymatic steps. In the related group of disorders, the sphingolipidoses, mutations in the genes that encode the individual degradative enzymes cause lysosomal accumulation of sphingolipids and often result in severe neurodegenerative disease.
How are lysosomes degraded?
There are two main degradation pathways that involve lysosomes: the degradation of extracellular substances by endocytosis and the degradation of cytoplasmic proteins and organelles by autophagy including macroautophagy, microautophagy, and CMA.
How gangliosides are degraded in lysosomes?
Lipids from the plasma membrane (PM) are degraded after endocytosis and internalization into intraendosomal luminal vesicles (IEVs) and intralysosomal luminal vesicles (ILVs). In the lysosome, ILV-bound (glyco-)sphingolipids are catabolized in a stepwise manner.
Are sphingolipids phospholipids and glycolipids?
Sphingolipids are phospholipids or glycolipids that contain the unsaturated amino alcohol sphingosine rather than glycerol. Phosphoglycerides (also known as glycerophospholipids) are the most abundant phospholipids in cell membranes.
What is different about sphingolipids relative to the other phospholipids?
The main difference between phospholipids and sphingolipids is that phospholipids consist of a glycerol backbone whereas sphingolipids consist of a sphingosine backbone.
Where are sphingolipids broken down?
In the final step of sphingolipid breakdown, sphingosine-1-phosphate is degraded by the enzyme sphingosine-1-phosphate lyase in the ER to produce hexadecenal and phosphoethanolamine.
Are glycolipids polar or nonpolar?
The saccharides that are attached to the polar head groups on the outside of the cell are the ligand components of glycolipids, and are likewise polar, allowing them to be soluble in the aqueous environment surrounding the cell.
Which of the following are usually digested or degraded by the lysosomes?
Lysosomes are membrane-enclosed organelles that contain an array of enzymes capable of breaking down all types of biological polymers—proteins, nucleic acids, carbohydrates, and lipids.
Which of the following are usually digested or degraded by lysosomes Class 9?
Answer: (c) old organelles of the cell.
How are endocytosed (glyco) sphingolipids degraded?
Endocytosed (glyco)sphingolipids are degraded, together with other membrane lipids in a stepwise fashion by endolysosomal enzymes with the help of small lipid binding proteins, the sphingolipid activator proteins (SAPs), at the surface of intraluminal lysosomal vesicles.
What are lysosomal pathologies caused by disturbed sphingolipid degradation?
Inborn errors of lysosomal function comprise mucopolysaccharidoses, glycoprotein-, glycogen storage disorders, mucolipidosis, sphingolipidoses, and others. This review focuses on the lysosomal pathologies, caused by disturbed sphingolipid degradation.
Do amphiphilic lipids decrease the electrostatic interaction between luminal and polycationic lysosomal vesicles?
As cationic amphiphilic lipids they should decrease the electrostatic interaction between the surfaces of luminal lysosomal vesicles and polycationic lysosomal proteins, namely the hydrolytic enzymes and lipid binding proteins SAPs.
What are the principles of lysosomal membrane digestion?
Principles of lysosomal membrane digestion: stimulation of sphingolipid degradation by sphingolipid activator proteins and anionic lysosomal lipids Annu Rev Cell Dev Biol. 2005;21:81-103.doi: 10.1146/annurev.cellbio.21.122303.120013.