Endoplasmic Reticulum, Golgi Complex, Lysosome, Peroxisome Asmarinah Depart of Medical Biology, Faculty of Medicine University of Indonesia

The structure of cells Schematic diagrams of b Schematic diagrams of a. “generalized” bacterial cell b. Plant cell c. Animal cell c

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

Ribosome 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.

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

Lysosome is an animal cell’s digestive organelles Contains approximately 50 different hydrolytic enzymes produced in the ERE and targeted to these organelles Enzymes have their optimal activity at an acid pH (= acid hydrolase), and can hydrolize every type of macro 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) - found in all eukaryotic cell - The site of synthesis and degradation of hydrogen peroxide (H2O2), a highly reactive and toxic oxiding agents Is mayor site of oxigen utilization, like mitochondria - Contains oxidatives enzymes, such as catalase and urate oxidase

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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