Endoplasmic Reticulum, Endoplasmic Reticulum, Golgi Complex, Lysosome, Golgi Complex, Lysosome,

PeroxisomePeroxisome

Asmarinah

Depart of Medical Biology, Faculty of Medicine

University of Indonesia

The structure of cells

a b

c

Schematic diagrams of

a. “generalized” bacterial cell

b. Plant cell

c. Animal cell

Intracellular compartment of eucaryotic cell

Example: Epithelial cell lines the male reproductive tract

Each organelle of the eucaryotic cell

Contains :

- characteristic set of enzyme

- specialized molecules

- distribution systems of transport

The composition of eukaryotic cell:

- Membrane system

-Cytoplasm/cytosol

-Organelles : Nucleus

Endoplasmic reticulum (ER)

Golgi apparatus

Mitochondria, in plants: chloroplast

Lysosome

Peroxisome

-Cytoskeleton

Endoplasmic Reticulum

-Constitutes more than half of total membrane of an average animal cell

-Is organized into a netlike labyrinth of branching tubules and flattened sacs extending throughout the cytosol

ER network in mammalian cell

ER is divided into two subcompartment:

a. the rough endoplasmic reticulum (RER) has ribosomes bound to its cytosolic surface

RER is the starting point of the biosynthetic pathway: the site of synthesis protein, carbohydrate chains and phospholipids

b. the smooth endoplasmic reticulum (SER) lacks assosiated ribosomes

-extensively developed in a number of the cell types

-Function, i.e:

* Synthesis of steroids hormones

* Detoxifications in the liver of a wide variety of organic compounds

• play role in protein biosynthesis • has no cell membrane• are small granule (25 nm) that can produce more than 40% of protein (70 kinds of proteins) and 60 % RNA. • found abundant in the surface of ER, but also found in mitochondria as well as in chloroplast• Ribosome are produced in nucleolus. • Each type of cell has different amount of ribosome Example: E. Coli has 1,500 ribosome.

Ribosome

Polyribosomes

Golgi complex

-has characteristic morphology consisting primary of flattened, disliked and membranous cisternae

- Receives lipids and protein from ER and dispatches them to a variety of destination

-is divided into several function distinct compartment, from the cis or entry face closest to the ER, to the trans or exit face at the opposite end

The cis face composed of an interconnected network, refers as, cis Golgi Network (CGN). The function is as a sorting station that distinguishes between protein to be shipped back to the ER and those that are allowed to proceed to the next Golgi station

The trans face containing a distinct network of tubules and vesicles, called trans Golgi Network (TGN), is sorting station for diifferent types of vesicle heading either to plasma membrane or to various intracellular destinations

LysosomeLysosome-is an animal cell’s is an animal cell’s

digestive organellesdigestive organelles

-Contains approximately 50 Contains approximately 50

different hydrolytic different hydrolytic

enzymes produced in the enzymes produced in the

ERE and targeted to these ERE and targeted to these

organellesorganelles

-Enzymes have their Enzymes have their

optimal activity at an acid optimal activity at an acid

pH (= acid hydrolase), and pH (= acid hydrolase), and

can hydrolize every type of can hydrolize every type of

macro moleculesmacro molecules

Lysosome range in size, from large size (over 1 um) to very small (25-50 nm in diameter)

Three pathways to degradation in lysosome

Peroxisome (microbody)Peroxisome (microbody) - found in all eukaryotic cell - found in all eukaryotic cell - The site of synthesis and degradation of - The site of synthesis and degradation of hydrogen peroxide (H2O2), a highly reactive and hydrogen peroxide (H2O2), a highly reactive and toxic oxiding agentstoxic oxiding agents

-Is mayor site of oxigen utilization, like mitochondria

- - Contains oxidatives Contains oxidatives enzymes, such as enzymes, such as catalase and urate catalase and urate oxidaseoxidase

References

Alberts et al., 2002. Molecular Biology of the Cell.

4 ed.

Karp G. 2005. Cell and Molecular Biology. 4 ed.

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