Endomembrane system(physiology)
2023-04-02 16:04:30 0 举报AI智能生成
A brief overview of the endomembrane system
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Endoplasmic reticulum(ER)
SER(free of ribosomes)
an interconnecting network of tubular membrane
Function
take part in the synthesis of various lipids
glycerol phospholipids(building membranes)
ceramides
sphingomyelin(the only nonglycerol phospholipid in cell membrane)is synthesized from ceramide in the goli apparatus.
fattey acids
steroids(e.g.hormones)
RER(covered with ribosomes)
the lumen of RER is connected to nuclear envelope
Function
Proteins synthesized on ribosomes of RER:
- Secretory proteins
- integral membrane proteins
- soluble proteins of organeles
Signal Recognition Particle(SRP)
- recognizes and binds to ER singal sequence
- interacts with the ribosome to block further translation
- binds to the ER membrane (docking protein:receptor protein)
the transport of the proteins
Modification and processing of newly synthesized proteins
glycosylation in the RER
the folding of proteins
the information of disulfide bonds within polypeptide
the lumen od RER contains:PDI -transfer incorrect disulfide bonds to correct dislfide bonds within the polypeptides.
Golgi complex
consists of a stack of flatted vesicles and tubules
Polarity organelle:has a cis face and a trans face
Functions:receives newly synthesized proteins and lipids from the ER and thenprocessing,sortingand distributes them to the plasma membrane,lysomes and secretory vesicles.
a site of O-linked glycosylation
Endosome
Lysosome
common in animal cells but rare in plant cells.
Structure
a tiny membrane-bound organelle found in the cytoplasm of all eukaryotic cells containing various acid hydrolytic enzymes that can digest every kind of biological molecule.
Marker enzyme:acid phosphatase
contain about 50 types of hydrolytic enzymes. All are acid hydrolases.
PH:5.0 in its interior
Lysosomes are involved in:
pinocytosis
phagocytosis
autophagy
exocytosis
endocytosis:pinocytosis and phagocytosis
Concerning Diseases
Autolysis
Lysosomal storage diseases
Physiological significance
① it effectively increases the surface area of the inner membrane of the cell and forms independent membrane compartments within the cell. The different physiological and biochemical processes in the cells can be carried out independently and without interference, and the whole metabolism level and function efficiency of the cells are greatly improved.
② The members of the intimal system exchange materials and information with each other through the formation of transport vesicles, so that a series of life activities in the cells can be orderly and stably carried out.
③ When the transport vesicles shuttle between various membrane structures for substance transport, the membrane components between the various members of the intima system and the membrane of the cell membrane are also constantly renewed and reorganized;
④ various membranous transport vesicles carry out material transport between the intimal system and the membrane, which communicates the interrelationship between the cell and the external environment. Finally, it embodies the integrity of the internal functional structure of the cell and the high unity of interaction with the external environment.
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