CELL ORGANELLES

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CELL ORGANELLES
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2 Types of the cell1. Prokaryotic cell
Consist of a single intracelullar compartment,
surrounded by a plasma membrane.2. Eukaryotic
cell Subdivided into functionally distinct,
membrane-enclosed compartments.
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The structure of cells
a
b
Schematic diagrams of a. generalized bacterial
cell b. Plant cell c. Animal cell
c
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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

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The composition of eukaryotic cell 1. Membrane
system 2. Cytoplasm/cytosol 3. Organelles
Nucleus Endoplasmic
reticulum (ER) Golgi
apparatus Mitochondria,
in plants chloroplast
Lysosome Peroxisome 4.
Cytoskeleton
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• 1. Plasma membrane
• - Serve as a selectivity permeable barrier
  between the living and nonliving world.
• Many vital biochemical processes take place in or
  on membrane surface, such as lipid metabolism
• The chemical composition of its is very
  different between prokaryotic and eukaryotic cell
• Plasma membrane in eukaryotic cell is
  constructed by lipid bilayer and protein that is
  impermeable to most hydrophilic molecules
• Intracellular membrane system create enclosed
  compartements ( organelles) that are separate
  from cytosol

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The view of a plasma membrane of eukaryotic cell
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Cell surface properties of bacteria
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• 2. Cytoplasm
• Consists of the cytosol and cytoplasmic
  organelles suspended in it
• Cytosol, constituing a little more than half the
  total volume of the cell, is the site of protein
  synthesis and degradation
• 3. Organells
• a. Nucleus
• The biggest organell of the cell
• The principal site of DNA and RNA synthesis

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• Nucleus membrane, consists of
• inner nuclear membrane, contains specifics
  protein that acts as binding site for chromatin
  and for the protein of nuclear lamina that
  provides structural support
• outer nuclear membrane, which is continuous
  with membrane of the ER (Endoplasmic Reticulum)

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Nucleus contains the main genome that is packaged
in chromosomes

• The principal structural features of chromosome
• An electron micrograph of human mitotic
  chromosomes
• A diagram of various classes of human chromosomes

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Chromosome packing occurs on several levels
Nucleosome
DNA histon
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Genome The totality of genetic information
belonging to a cell or an organism in
particular, the DNA that carries this information
Genomics The science of studying the DNA
sequences and properties of entire genomes
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Nucleolus Structure in the nucleus where
ribosomal RNA (rRNA) is transcribed and ribosomal
subunits are assambled - rRNA specific RNA
molecules that form part of the structure of a
ribosome and participate in the synthesis of
proteins. Often distinguished by their
sedimentation coefficient 28S rRNA or 5S rRNA
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• b. 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
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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
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c. Ribosome

• is small granulle ( 25 nm),
• found in eukaryotic, prokaryotic and plant
  cell
• located in the surface of mitochondria or
• chloroplast, but mainly in the surface of
• endoplasmic reticulum,
• doesnt have cell membrane
• produced in nucleolus
• composed by ribosomal RNA and ribosomal protein
  
• that associates with mRNA
• catalyzed of protein synthesis

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Ribosome and its function in protein synthesis
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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

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d. 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
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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
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e. Mitochondria - The organelle that be able to
utilize the oxygen for the energy extraction.
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The structure of mitochondria

• contains two membranes
• outer mitochondrial membrane
• inner mitochondrial membrane
• There is two aqueous compartment
• Matrix, within the interior
• Intermembrane space, between
• OMM and IMM

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Role of mitochondria

• produce ATP
• 5 respiration enzyme complexes
• complex I (NADH oxydoreductase Ubiquinone)
• complex II (suksinat oxydoreductase ubiquinone)
• complex III (ubiquinol oxydoreductase sitokrom
  c)
• complex IV (Cytocrome c oxydase)
• complex V (ATPsynthase).

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Mitochondrial DNA

• Chromosome No. 25
• Genome ? circular double stranded DNA
• Maternal inherited
• Mito DNA 16.569 bp
• Nuclear DNA 3 x 109 bp

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• f. Lysosome
• is an animal cells 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

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Lysosome range in size, from large size (over 1
um) to very small (25-50 nm in diameter)
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Three pathways to degradation in lysosome
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Phagocytosis Process by which particulate
material (particle or microorganism) is
endocytosed (eaten) by a cell
Endocytosis Uptake of material into a cell by an
invagination of plasma membrane and its
internalization in a membrane-bounded vesicle
Autophagy Digestion of worn-out organelles by
the cells own lysosomes
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g. 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

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Peroxisome contain one or more enzymes that use
molecular oxygen to remove hydrogen atoms from
specific organic substrates in an oxidative
reaction that produces hydrogen peroxide (H2O2)
RH2 O2 ? R H2O2 Catalase utilizes the
H2O2 generated by other enzymes in the organelle,
to oxidize a variaty of other substrates 2
H2O2 R H2 ? R 2 H2O
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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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