Organel Sel
Sel :
= Unit dari struktur dan fungsi organisme
= Unit terkecil dari kehidupan
Sel
Jaringan
Organ
Organisme
Jenis sel, ada 2 yaitu:
1. Sel prokariota
(Pro : ‘sebelum’) + (karyon : kernel/nukleus)
Sel yang “tidak mempunyai nukleus”  materi
genetik ada pada daerah nukleoid
2. Sel eukariota
(Eu: “sebenarnya”) + (karyon)
Sel yang mempunyai inti sebenarnya, dibungkus
oleh selubung/membran
Struktur sel
a
b
Diagram:
a. Sel bakteri, umumnya
Ukuran: 1 – 10 um
c
Paling kecil: mikoplasma
(0,1 – 1 um)
b. Sel tumbuhan
c. Sel hewan
Ukuran sel hewan & tumbhn:
10 – 100 um
Komposisi dari sel eukarita:
1. Sistem endomembran
2. Sitoplasma
3. Organel (dibentuk oleh sistem membran di dalam sel):
- Nucleus/inti
- Reticulum Endoplasma (RE)
- Badan Golgi
- Mitochondria, in plants: chloroplast
- Lysosome
- Peroxisome
4. Sitoskeleton
Contoh: Sel epitel pada saluran reproduksi pria
1. Plasma membran
-Berfungsi sbg pembatas yang selektif permeabel
antara lingkungan yang hidup dan yang mati
- Banyak proses biokimia penting terjadi di permukaan
membran plasma. Mis: metabolisme lipid
- Komposisi kimia membran plasma sel prokariota
berbeda dengan sel eukariota
- Lipid dan protein merupakan bahan penyusun utama
membran, juga sering ditemukan karbohidrat
- Penyusunan molekul-molekul tsb dlm plasma membran,
disebut dgn model mozaik fluida ( lipid bilayer
dengan protein tersisip diantaranya, diperkenalkan
oleh Singer & Nicolson, 1972)
Membran plasma sel eukariota
Permukaan dinding sel pada bakteri
2. Sitoplasma
- terdiri dari medium semicair yg disebut sitosol,
di dalamnya terletak organel
- Sitosol, volumenya lebih 50% dari volume sel,
merupakan tempat untuk sintesis dan degradasi
protein
3. Organel
a. Nukleus/inti sel
- Organel paling besar/menyolok (rata2 diameter 5 um)
- tempat untuk sintesis DNA dan RNA
- Membran inti terdiri atas :
* membran dalam, yg berisi protein spesifik yg mengikat
kromatin dan lamina inti. Lamina inti merupakan filamen
yang memperkuat struktur inti
* membran luar, yang berlanjut/berhubungan dengan
membran organel lain yaitu reticulum endoplasma
Masing-masing merupakan lipid bilayer. Pada membran
inti terdapat pori-pori, tempat keluar masuk molekul.
-Di dalam inti terdapat DNA yang diorganisasikan bersama
protein histon, membentuk kromatin.
- Ketika sel siap membelah, kromatin memadat membentuk
kromosom; membran inti terurai
A
B
A. Structur kromosom
B. Kromosom dilihat dengan mikroskop elektron
C. Berbagai jenis bentuk kromosom
C
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
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
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
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,
• doesn’t have cell membrane
• produced in nucleolus
• composed by ribosomal RNA and ribosomal protein
that associates with mRNA
• catalyzed of protein synthesis
Ribosome and its function in protein
synthesis
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
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
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
e. Mitochondria
- The organelle that be able to utilize the oxygen for
the energy extraction.
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
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).
Mitochondrial DNA
Chromosome No. 25
Genome  circular double
stranded DNA
Maternal inherited
Mito DNA : 16.569 bp
Nuclear DNA : 3 x 109 bp
f. 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
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 cell’s own
lysosomes
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
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
References
Alberts et al., 2002. Molecular Biology of the Cell.
4 ed.
Karp G. 2005. Cell and Molecular Biology. 4 ed.
Thanks you