细胞生物学_intracellular compartments
The Compartmentalization of Eukaryotic Cells
Three categories of compartments 三种区室
- the cytoplastic matrix 细胞质基质
- the endomembrane system
ER, Golgi apparatus, Lysosomes - membrane-bound organelles
mitochondria, peroxisomes, and the nucleus
Cytoplasmic Matrix
细胞质基质,也叫做cytosol胞质溶胶
highly ordered, key is cytoskeleton
function
- Performs most of intermediary metabolism.
执行大部分中间代谢 - The site of protein and fat synthesis
- The function of cytoskeleton
维持细胞形态,运动,物质运输,组织细胞质基质 - The Functions of membrane system
divide the cytoplasm into compartments,载体蛋白和通道蛋白maintain the ion gradient across membrane - Protein post-translational modification and selective degradation
蛋白质翻译后修饰和选择性降解
Endoplasmic Reticulum ER 内质网
A central role in both lipid, protein, sugar synthesis.
a network of tubules (管状) and flattened sacs (扁平囊状)
rER
rough ER 粗面内质网
Has ribosomes on the cytosolic side of continuous flattened sacs.
Site of membrane and secretory protein synthesis
sER
smooth ER 光面内质网
Is an interconnecting network of tubular membrane elements
Lipid synthesis, signal transduction
function
The main function of rER is to synthesize protein.
分泌蛋白,膜上的蛋白,细胞器中的蛋白sER is an important site for lipid synthesis.
Modification and processing of proteins
① glycosylation糖基化
② form disulide bonds二硫键
③ fold and assembly
④ specific hydorlysis and cleavageFolding and assembly of newly synthesized polypeptide chains
Other Functions of sER
内质网储存酶(肝细胞用于解毒),存储Ca2+(肌浆网)
Golgi Apparatus 高尔基体
distribution center
the factory of sugar synthesis in cells
structure
分cis和trans
cis靠近细胞核, 凸面
trans靠近细胞膜, 凹面
CGN & cis cisterna
CGN accepts the newly synthesized substances from ER and sort into the medial cisternamedial cisterna
Most of the glycosyl modification and processing process occurstrans cisterna & TGN
Sorting and packaging of proteins to form vesicles, and transport of proteins to their final destinations.
Some “late” protein modifications also occur in TGN.
function
Protein packaging and sorting
有三个pathways
① lysosome
② regulated secretion pathway
③ constitutive secretion pathway
The glycosylation modification of most proteins or lipids
① The glycosylation of most proteins promote protein folding and enhance protein stability
促进蛋白折叠,增强稳定性
② Sugar chain of glycoprotein is used as a guiding signal for Golgi apparatus to package and sort proteins
指导打包和分类
③ Sugar chains on the cell surface and extracellular matrix are involved in the cell recognition, adhesion
细胞表面的糖链参与识别和黏连
④ Sugar chains also affect the water solubility and charge of proteins
影响水溶性和电荷
- Protease hydrolysis
① 切掉proprotein蛋白原不需要的部分,变成mature peptides,比如胰岛素
② 一些蛋白质在粗面内质网（rER）合成期间是含有多个相同氨基酸序列的前体蛋白，然后在高尔基体中被水解形成相同的活性肽
③ Same protein precursor前体 may be processed in different ways in different cells to produce different kinds of peptides
Lysosomes 溶酶体
monolayer 单层膜
filled with variety of acid hydrolases
多种酸性水解酶
酶在粗面内质网合成,经高尔基体出芽形成
main function is to intracellular digestion 胞内消化
structure
溶酶体膜上有
- embedded H+ pump
嵌入式H+泵,溶酶体内酶最适pH是5 - multiple carrier proteins
- Intense glycosylation of membrane proteins
高度糖基化的蛋白,防止被降解
divide
Primary/early lysosome (初级溶酶体)
Secondary/late lysosome (次级溶酶体)
Residual body (后溶酶体即残质体)
function
The basic function of lysosome is intracellular digestion
which is of great significance for maintaining the normal metabolic activity of cells and preventing microbial infection
维持正常代谢活性和防止微生物感染
有三种作用途径
- Endocytosis (内吞作用)
- Phagocytosis (吞噬作用)
- Autophagy (自噬作用)
Peroxisomes 过氧化物酶体
monolayer 单层膜
contain oxidases 氧化酶
pH 7.0, 酶在细胞质基质中合成
Peroxisome is a heterogeneous organelle
异质细胞器,不同生物,不同发育阶段该细胞器的形态以及所含酶有很大不同
主要有两种酶
- FAD-dependent oxidase
oxidize the substrate to form H2O2
把底物氧化成H2O2 - Catalase
decompose H2O2 to form water and oxygen
把H2O2分解成水和氧气
Two enzymes are coupled to eliminate the toxicity of H2O2.
Peroxisome can degrade biological macromolecules
decompose molecules such as fatty acids to provide heat
