Endomembrane System
2017-09-29 11:11:09 0 举报AI智能生成
molecular cell biology - endomembrane system
作者其他创作
大纲/内容
cell structure
cytoplasm
material between nuclear membrane and plasma membrane
cytosol
fluid portion of cytoplasm
gel-like substance composed of water (80%), nutrients and electrolytes
maintain stable internal environment of cells
hold the organelles
organelles
membrane bound specialized structure found inside eukaryotic cells between plasma and nuclear membrane
endoplasmic reticulum (ER)
accounts for 50% membrane of whole cell
functions
manufactures membranes and performs many other biosynthetic functions
transports proteins synthesized by ribosomes to the cell membrane where they will be used or secreted by the cell
types
smooth ER
no ribosomes attached on it
functions
many metabolic processes
synthesize lipids, phospholipids, steroids and sex hormones
catalyze hydrolysis of glycogen (in liver) into glucose
detoxify drugs and poisons (in liver)
alcohol, antibiotics, barbiturates...
storage area of Ca2+ in muscle cells (sarcoplasmic reticulum)
rough ER
many ribosomes bind to it
ribosome - protein maker
integral membrane proteins
secretory proteins
to the cytosol or outside the cell
soluble proteins
within the endomembrane system (enzymes in the lysosomes)
In the synthesis of integral membrane protein on ribosome of RER, there is a signal sequence
on the polypeptide chain. The signal sequence will bind with SRP, and the SRP will combine with
SRP receptor, lead the polypeptide chain to ER membrane.
functions
fold and modify secretory proteins (glycoproteins) within cisternae space and transport
attaches carbohydrates called oligosaccharides to growing and folding polypeptide chain
delivers products to other locations or next stage in the cell (such as golgi apparatus)
membrane factory
membrane bound proteins
phospholipids
transport vesicles
golgi apparatus
structure
cis side (towards nucleus)
receives material by fusing with vesicles
trans side (towards outside)
buds off vesicles that travel to other sites
functions
receives, sorts, processes and packages material from ER
transports molecules in secretory vesicles that fuse with cytoplasmic membrane or other destinations
lysosomes / peroxisome
lysosomes
structure
membrane-bounded sac of hydrolytic enzymes that digests macromolecules
enzymes and membrane of lysosomes are synthesized by rough ER and transferred to golgi complex
all enzymes have their optimal activity at and acid pH (4.6-5)
classification
primary lysosome
bud off from the trans surface of golgi apparatus
contains hydrolytic enzymes
exogenous and endogenous materials digestive organelles
secondary lysosome
primary lysosome fused with
endosome
autophagolysosome
phagosome
phagolysosome
heterophagic lysosome
residual body
routes of products delivery
pinocytosis
receptor mediated endocytosis
endocytosis
phagocytosis
autophagy
"self eating" of old or injured organelles
important in cell degradation during apoptosis
functions
cellular digestion
lysosome fuse with food vacuoles
polymers are digested into monomers pass to cytosol to become nutrients of cell
fuse with organelles or macromolecules in cytosol to replace organelle and recycle materials (autophagy)
cytoimmune and defence
fuse with debris or potentially dangerous microorganisms
mediate sperm-egg fusion
acrosome release lysosome to mediate cell fusion
development regulation
diseases
lysosomal storage diseases
(rare but fatal)
Tay-Sachs disease
Gaucher's disease
peroxisome
another digestive enzyme sacs in both animals and plants
similar structure to lysosome
functions
breakdown fatty acids to sugars
produce energy
detoxify cell
catalases degrade H2O2 into H2O and O2
produce peroxide (H2O2) - toxic to cell
oxidases use O2 to oxidize organic substance and produce hydrogen peroxide
reactive oxygen species (ROS)
cause damage to lipids, proteins, DNA
reduce by catalase and superoxide dismutase(SOD)
synthesize bile acid
metabolize purines and alcohol
diseases
adrenoleukodystrophy
Zellweger syndrome
vesicles
mitochondria
is NOT part of endomembrane system!!!
only in animal
produce ATP
mitochondria convert the chemical energy of reduced carbon compounds into ATP
three major steps
production of reducing equivalents (NADH, FADH2) from glycolysis, fatty acid oxidation, and the citric acid cycle
electron transport and generation of proton motive force
phosphorylation - synthesis of ATP, driven by the proton motive force
compartments
outer membrane
with large aqueous channels made of a protein called porin
permeable to larger molecules
inner membrane
highly folded into invaginations called cristae
respiratory chain and ATP synthase
most charged molecules cannot pass through
ETC
intermembrane space
cristae
matrix
enzymes of the citric acid cycle
mtDNA - several copies, ribosomes, tRNA
another set of DNA, can be transcript and translate on its own
electron transport chain (ETC)
unique characters
have their own DNA
have their own ribosomes inside
mtDNA is a very compact genome
genes attached end to end, with mRNA regions interspersed among rRNA and tRNA genes
all mitochondria in the body came from the mother
are not part of the genetic code in the nucleus of cells
origin
endosymbiosis
收藏
0 条评论
下一页
