ORGANISASI SEL
Delayota Science Club (DSC)
Januari 2011
Pengertian Sel Sel ditemukan pertama kali oleh Robert Hooke yang mengamati sayatan tanaman gabus (Quercus suber) tahun 1665. Theodore Schwann dan Mathias Schleiden: Sel merupakan unit struktural terkecil penyusun makhluk hidup. Max Schlutze: Sel merupakan unit fungsional terkecil penyusun makhluk hidup. Rudolf Virchow: Setiap sel berasal dari sel lain (omnis cellulae ex cellulae) Walter Flemming dan Eduard Strasburger: Sel merupakan unit reproduksi makhluk hidup.
Perkembangan
LM 1,000×
Pengamatan Sel
Figure 4.1C
TEM 2,800 ×
SEM 2,000 ×
Figure 4.1B
Figure 4.1D
Sel selalu berukuran mikroskopis (kecil) karena sel yang berukuran kecil memiliki rasio luas permukaan/volume yang lebih besar daripada sel dengan ukuran yang sama. 10 µm
30 µm
30 µm
Surface area of one large cube = 5,400 µm2
10 µm
Total surface area of 27 small cubes = 16,200 µm2
Macam-macam Sel
Colorized TEM 15,000 ×
Sel prokariotik: belum memiliki organela bermembran Sel eukariotik: memiliki organela bermembran Prokaryotic cell Nucleoid region
Nucleus
Eukaryotic cell
Organelles
Sel Prokariotik Umumnya berukuran lebih kecil daripada sel eukariotik Tidak memiliki membran inti (karioteka) Prokaryotic flagella
Ribosomes Capsule Cell wall Plasma membrane
Nucleoid region (DNA)
Pili
Sel Eukariotik Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Nucleus
Flagellum Not in most plant cells Lysosome Ribosomes
Centriole Peroxisome Microtubule Intermediate Cytoskeleton filament Microfilament
Golgi apparatus Plasma membrane Mitochondrion
Sel Hewan
Sel Eukariotik Nucleus
Rough endoplasmic reticulum Ribosomes
Golgi apparatus Central Not in vacuole animal Chloroplast cells Cell wall
Smooth endoplasmic reticulum Microtubule Intermediate Cytoskeleton filament Microfilament
Mitochondrion Peroxisome Plasma membrane
Sel Tumbuhan
Struktur Sel Eukariotik Nukleus (inti sel) Sitoplasma (cairan sel) Sistem Endomembran
Ribosom Retikulum Endoplasma Badan Golgi Lisosom Vakuola
Organel-organel lain
Mitokondria Plastida Peroksisom Glioksisom
Sitoskeleton Mikrofilamen Mikrotubul Filamen antara
Membran sel
Inti Sel (Nukleus) The nucleus contains most of the cell’s genes and is usually the most conspicuous organelle The nuclear envelope encloses the nucleus, separating it from the cytoplasm The nuclear membrane is a double membrane; each membrane consists of a lipid bilayer In the nucleus, DNA and proteins form genetic material called chromatin Chromatin condenses to form discrete chromosomes The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis.
Nucleus 1 µm
Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane
Nuclear pore
Pore complex
Surface of nuclear envelope
Rough ER Ribosome
1 µm
0.25 µm
Close-up of nuclear envelope
Pore complexes (TEM)
Nuclear lamina (TEM)
Retikulum Endoplasma (RE)
Smooth ER, which lacks ribosomes Rough ER, with ribosomes studding its surface
Nuclear envelope
Ribosomes Rough ER TEM 45,000×
The endoplasmic reticulum Smooth ER (ER) accounts for more than half of the total membrane in Rough ER many eukaryotic cells The ER membrane is continuous with the nuclear envelope There are two distinct regions Smooth ER of ER:
The smooth ER Synthesizes lipids Metabolizes carbohydrates Detoxifies poison Stores calcium
The rough ER Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates) Distributes transport vesicles, proteins surrounded by membranes Is a membrane factory for the cell
Ribosom Ribosomes are particles made of ribosomal RNA and protein Ribosomes carry out protein synthesis in two locations: In the cytosol (free ribosomes) On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)
Large subunit Small subunit
Transport vesicle buds off
4
Ribosome
3
Secretory (glyco-) protein inside transport vesicle Sugar chain
1 2
Glycoprotein
Polypeptide Rough ER
Badan Golgi cis face (“receiving” side of Golgi apparatus)
Cisternae
trans face (“shipping” side of Golgi apparatus)
The Golgi apparatus (dictiosom) consists of flattened membranous sacs called cisternae Functions of the Golgi apparatus: Modifies products of the ER Manufactures certain macromolecules Sorts and packages materials into transport vesicles
Lisosom Rough ER
1
A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids
Transport vesicle (containing inactive hydrolytic enzymes) Golgi apparatus
Plasma membrane
Engulfment of particle
Lysosome engulfing damaged organelle
2
“Food” Lysosomes
3
5 4 Food vacuole
Digestion
Beberapa peran lisosom: Mencerna makanan (fagositosis), termasuk memakan bibit penyakit. Menghancurkan organel yang tidak digunakan lagi (autofagi).
Kerusakan lisosom dapat berakibat fatal bagi organisme tersebut.
Lysosome
Digestive enzymes
Lysosome
Plasma membrane
Peroxisome Digestion Food vacuole Vesicle
(a) Phagocytosis
(b) Autophagy
Mitochondrion
Digestion
Vakuola Vakola dilingkupi oleh membran “tonoplas” Types of vacuole:
Nucleus
Contractile vacuoles
LM 650×
Food vacuoles are formed by phagocytosis Contractile vacuoles, found in many freshwater protists, pump excess water out of cells Central vacuoles, found in many mature plant cells, hold organic compounds and water
Mitokondria Mitochondria are in nearly all eukaryotic cells They have a smooth outer membrane and an inner membrane folded into cristae The inner membrane creates two compartments: intermembrane space and mitochondrial matrix Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix
Cristae present a large surface area for enzymes that synthesize ATP
Plastida Plastida merupakan organela yang mempunyai fungsi khusus. Leukoplas: bagian plastida yang tidak berwarna, terdiri dari: Amiloplas: tempat menyimpan amilum Proteoplas: tempat menyimpan protein Elaeloplas: tempat menyimpan lemak
Khromatophora: bagian plastida yang berwarna, terdiri dari: Khromoplas berwarna orange karena menyimpan karoten dan xantofil Kloroplas berwarna hijau karena menyimpan klorofil Feoplas berwarna biru karena menyimpan fikosantin Rhodoplas berwarna merah karena menyimpan fikoeritrin
Kloroplas Merupakan bagian dari Plastida. Mengandung pigmen klorofil dan enzim-enzim fotosintetik. Berfungsi dalam proses fotosintesis, yakni mengubah energi cahaya menjadi energi kimia (karbohidrat). Dijumpai pada tumbuhan hijau dan alga (ganggang).
Struktur Kloroplas:
Sitoskeleton The cytoskeleton is a network of fibers extending throughout the cytoplasm It organizes the cell’s structures and activities, anchoring many organelles Microfilaments of actin enable cells to change shape and move.
Tubulin subunit
Actin subunit
Fibrous subunits 7 nm
Microfilament
Intermediate filaments reinforce the cell and anchor cer tain organelles Microtubules give the cell rigidity and provide anchors for organelles and act as tracks for organelle movement
25 nm
10 nm Intermediate filament
Microtubule
Cillia dan Flagella Merupakan alat gerak yang dimiliki beberapa sel, umumnya pada sel hewan. Gerakan cillia dan flagella diatur oleh mikrotubulus Cilia and flagella memiliki cara gerak yang berbeda.
Cara gerak flagella (bulu cambuk)
Cara gerak cillia (rambut getar)
Dinding Sel The cell wall is an extracellular structure that distinguishes plant cells from animal cells The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein. Bacterial cell walls are made of peptidoglican, a polymer from n-acetil glucosamine and n-acetil murein. Fungal cell walls usually are made of chitin.
Dinding sel tumbuhan mengalami penebalan sedemikian rupa sehingga dapat dibedakan menjadi beberapa lapisan: Dinding primer: tersusun oleh selulosa Dinding sekunder: tersusun oleh lignin Lamela tengah: tersusun oleh pektin
Penebalan pada dinding sel tumbuhan dapat terjadi dengan dua cara, yakni: Aposisi Intususepsi Secondary cell wall Primary cell wall Middle lamella
Intercellular junctions Intercellular junctions facilitate contact between neighbouring cells. There are several types of intercellular junctions. Plasmodesmata: channels that perforate plant cell walls Tight junctions: membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid Desmosomes: (anchoring junctions) fasten cells together into strong sheets Gap junctions: (communicating junctions) provide cytoplasmic channels between adjacent cells
Tight junction Tight junctions prevent fluid from moving across a layer of cells
0.5 µm
Tight junction Intermediate filaments
Desmosome
Gap junctions
Space between cells Plasma membranes of adjacent cells
Desmosome
1 µm
Extracellular matrix Gap junction
0.1 µm
Membran Sel A membrane is a collage of different proteins embedded in the fluid matrix of the lipid bilayer Proteins determine most of the membrane’s specific functions Peripheral proteins are not embedded Integral proteins penetrate the hydrophobic core and often span the membrane Integral proteins that span the membrane are called transmembrane proteins
Fibers of extracellular matrix (ECM) Glycoprotein Carbohydrate
Glycolipid EXTRACELLULAR SIDE
Cholesterol Microfilaments of cytoskeleton
Peripheral proteins
Integral protein
CYTOPLASMIC SIDE
Fungsi Membran Sel Signal Enzymes
Receptor
ATP
Transport
Enzymatic activity
Signal transduction
Glycoprotein
Cell-cell recognition
Intercellular joining
Attachment to the cytoskeleton and extracellular matrix (ECM)
Transport Melalui Membran Membran sel berfungsi untuk transportasi zat-zat keluarmasuk sel. Transport aktif adalah transportasi zat-zat keluar masuk membran yang membutuhkan energi, biasanya berupa ATP. Transport aktif dapat berupa: Endositosis Eksositosis Pompa Na/K
Transport pasif adalah transportasi zat-zat keluar masuk membran yang tridak membutuhkan energi. Transport pasif dapat berupa: Difusi Difusi terfasilitasi Osmosis
Difusi Difusi merupakan perpindahan molekul-molekul zat terlarut dari larutan yang pekat (hipertonis) ke larutan yang lebih encer (hipotonis) gradien konsentrasi. Molecules of dye
Membrane (cross section)
WATER
Net diffusion
Net diffusion
Equilibrium
Difusi Fasilitasi Difusi fasilitasi merupakan proses difusi yang “dibantu” oleh protein transport pada membran sel, baik protein channel maupun carrier. EXTRACELLULAR FLUID
Channel protein
Carrier Protein Solute CYTOPLASM
Osmosis Osmosis merupakan perpindahan molekulmolekul zat pelarut (air) dari larutan encer ke larutan pekat melalui membran semi permeabel. Lower concentration of solute (sugar)
Higher concentration of sugar
H2O
Osmosis Membran semi permeabel
Same concentration of sugar
Proses osmosis membantu menjaga tekanan air di dalam sel. Hypotonic solution
Isotonic solution
Hypertonic solution
Animal cell H2O
H2O
Turgid (normal)
H2O
H2O
Flaccid
H2O
Shriveled
Normal
Lysed Plant cell
H2O
H2O
H2O
Plasmolyzed
Transport Aktif EXTRACELLULAR [Na+] high FLUID [K+] low
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+ CYTOPLASM
[Na+] low [K+] high
Na+
Cytoplasmic Na+ bonds to the sodium-potassium pump
P
Extracellular K+ binds to the protein, triggering release of the phosphate group.
ATP P ADP
P
Na+ binding stimulates phosphorylation by ATP.
Phosphorylation causes the protein to change its conformation, expelling Na+ to the outside.
Loss of the phosphate restores the protein’s original conformation.
K+ is released and Na+ sites are receptive again; the cycle repeats.
P
Eksositosis dan Endositosis Exocytosis: transport vesicles migrate to the membrane, fuse with it, and release their contents. Endocytosis: the cell takes in macromolecules by forming vesicles from the plasma membrane. Endocytosis is a reversal of exocytosis, involving different proteins • Three types of endocytosis: Phagocytosis (“cellular eating”): Cell engulfs particle in a vacuole Pinocytosis (“cellular drinking”): Cell creates vesicle around fluid Receptor-mediated endocytosis: Binding of ligands to receptors triggers vesicle formation
