ORGANISASI SEL. Delayota Science Club (DSC) Januari 2011

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1 ORGANISASI SEL Delayota Science Club (DSC) Januari 2011

2 Pengertian Sel Sel ditemukan pertama kali oleh Robert Hooke yang mengamati sayatan tanaman gabus (Quercus suber) tahun 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.

3 LM 1,000 Figure 4.1B Perkembangan Pengamatan Sel SEM 2,000 TEM 2,800 Figure 4.1C Figure 4.1D

4 Sel selalu berukuran mikroskopis (kecil) karena sel yang berukuran kecil memiliki rasio luas permukaan/volume yang lebih besar daripada sel dengan ukuran yang sama. 30 µm 10 µm 30 µm 10 µm Surface area of one large cube = 5,400 µm 2 Total surface area of 27 small cubes = 16,200 µm 2

5 Macam-macam Sel Sel prokariotik: belum memiliki organela bermembran Sel eukariotik: memiliki organela bermembran Nucleoid region Prokaryotic cell Nucleus Colorized TEM 15,000 Eukaryotic cell Organelles

6 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

7 Sel Eukariotik Rough endoplasmic reticulum Smooth endoplasmic reticulum Nucleus Not in most plant cells Cytoskeleton Flagellum Lysosome Centriole Peroxisome Microtubule Intermediate filament Microfilament Mitochondrion Golgi apparatus Ribosomes Plasma membrane Sel Hewan

8 Sel Eukariotik Nucleus Rough endoplasmic reticulum Ribosomes Golgi apparatus Smooth endoplasmic reticulum Microtubule Not in animal cells Central vacuole Chloroplast Cell wall Intermediate filament Microfilament Cytoskeleton Mitochondrion Peroxisome Plasma membrane Sel Tumbuhan

9 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

10 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.

11 1 µm Nuclear envelope: Inner membrane Outer membrane Nucleolus Chromatin Nucleus Nuclear pore Pore complex Surface of nuclear envelope 0.25 µm Ribosome Rough ER 1 µm Close-up of nuclear envelope Pore complexes (TEM) Nuclear lamina (TEM)

12 Retikulum Endoplasma (RE) The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells The ER membrane is continuous with the nuclear envelope There are two distinct regions of ER: Smooth ER, which lacks ribosomes Rough ER, with ribosomes studding its surface Smooth ER Rough ER Smooth ER Nuclear envelope Ribosomes Rough ER TEM 45,000

13 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

14 Ribosom Ribosomes are particles made of ribosomal RNA and protein Ribosomes carry out Transport vesicle buds off 4 protein synthesis in two Ribosome locations: In the cytosol (free ribosomes) On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes) 1 Polypeptide 2 3 Glycoprotein Large subunit Small subunit Secretory (glyco-) protein inside transport vesicle Sugar chain Rough ER

15 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

16 Lisosom Rough ER A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids Food Plasma membrane 3 Engulfment of particle Food vacuole 1 Transport vesicle (containing inactive hydrolytic enzymes) Lysosomes Golgi apparatus 2 Lysosome engulfing damaged organelle 4 Digestion 5

17 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 Digestion Peroxisome Food vacuole Vesicle Mitochondrion Digestion (a) Phagocytosis (b) Autophagy

18 Vakuola Vakola dilingkupi oleh membran tonoplas Types of vacuole: 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 Nucleus Contractile vacuoles LM 650

19 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

20 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

21 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:

22 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. 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 Actin subunit Microfilament 7 nm Fibrous subunits 10 nm Intermediate filament Tubulin subunit Microtubule 25 nm

23 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)

24 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.

25 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

26 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

27 Tight junctions prevent fluid from moving across a layer of cells Tight junction 0.5 µm Tight junction Intermediate filaments Desmosome Gap junctions Desmosome 1 µm Space between cells Plasma membranes of adjacent cells Extracellular matrix Gap junction 0.1 µm

28 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

29 Fibers of extracellular matrix (ECM) Glycoprotein Carbohydrate Glycolipid EXTRA- CELLULAR SIDE Cholesterol Microfilaments of cytoskeleton Peripheral proteins Integral protein CYTOPLASMIC SIDE

30 Fungsi Membran Sel Enzymes Signal ATP Receptor Transport Enzymatic activity Signal transduction Glycoprotein Cell-cell recognition Intercellular joining Attachment to the cytoskeleton and extracellular matrix (ECM)

31 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

32 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

33 Difusi Fasilitasi Difusi fasilitasi merupakan proses difusi yang dibantu oleh protein transport pada membran sel, baik protein channel maupun carrier. EXTRACELLULAR FLUID Channel protein Solute Carrier Protein CYTOPLASM

34 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 Same concentration of sugar H 2 O Membran semi permeabel Osmosis

35 Proses osmosis membantu menjaga tekanan air di dalam sel. Animal cell Hypotonic solution Isotonic solution Hypertonic solution H 2 O H 2 O H 2 O H 2 O Lysed Normal Shriveled Plant cell H 2 O H 2 O H 2 O H 2 O Turgid (normal) Flaccid Plasmolyzed

36 Transport Aktif EXTRACELLULAR FLUID [Na + ] high [K + ] low Na + Na + Na + Na + Na + Na + Na + Na + CYTOPLASM Na+ [Na + ] low P ATP [K + ] high ADP P Cytoplasmic Na + bonds to the sodium-potassium pump Na + binding stimulates phosphorylation by ATP. Phosphorylation causes the protein to change its conformation, expelling Na + to the outside. P P Extracellular K + binds to the protein, triggering release of the phosphate group. Loss of the phosphate restores the protein s original conformation. K + is released and Na + sites are receptive again; the cycle repeats.

37 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

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