lect3-sist slpt sitoplasmik.ppt

Sistem selaput sitoplasmik (selaput interna)

• Diperlukan bagi sel berukuran besar utk mencukupi kebutuhan enzim utk kegiatan sel

• Merupakan invaginasi/evaginasi berulang2 selaput sel

• Membagi sitoplasma menjadi bbrp ruang (kompartemen) ruang & slpt pembatas = organel

• RE, bdn golgi, lisosom & mikrobodi 1 sistem

Endomembrane System

• Many membranes are interrelated directly through physical continuity or indirectly through transport vesicles

Endoplasmic reticulum

•Klp membran ganda yg bertumpuk2, tdpt diantara membran sel & inti.

•Tdpt ribosom REK•Ribosom bebas REH

Endoplasmic Reticulum

• Smooth E.R. (no ribosomes attached), synthesizes steroids, metabolizes carbohydrates, stores calcium

• Rough E.R. (has ribosomes), manufactures proteins for secretion

Endoplasmic Reticulum

Endoplasmic reticulum (ER)

Ribosomes

• Free ribosomes (ribosomes in cytoplasm)

• Bound ribosomes (ribosomes attached to endoplasmic reticulum)

• Both carry out protein synthesis

Ribosomes

• Ribosom prokariot berukuran kecil (70S) 2 sub unit : 30S & 50S svedberg unit

• Ribosom eukariot 80S 2 sub unit 40S & 60S

REK menghasilkan protein & menyusun membran

• The rough ER manufactures membranes• Ribosomes on its surface produce proteins

1 2

3

4Transport vesiclebuds off

Ribosome

Sugarchain

Glycoprotein

Secretory(glyco-) proteininside transportvesicle

ROUGH ER

Polypeptide

Ribosomes

REH memiliki fgs bervariasi

• Smooth ER synthesizes lipids

• In some cells, it regulates carbohydrate metabolism and breaks down toxins and drugs

Golgi Apparatus

• Finish, sort, and “ship” many products of the cell

• Synthesize macromolecules• Store and export products of E.R.• Deskripsi :

Klp 5-8 kantung membran bbtk mangkuk ( cistenae ) dg ujung menggelembung & menempel satu sama lain.

Golgi Apparatus

Golgi aparatus

• Bdn golgi bbtk polar, tdr atas bagian cis dmn protein masuk, & bagian trans dmn protein keluar.

• Dibagi2 dlm kompartemen/ruang2 yg berbeda dg processing enzymes yg spesifik.

• ± tdpt 20 bdn golgi pd tiap sel, vary depending on the function of the cell

The Golgi apparatus

What does it do?

• Utk distribusi & pusat lalulintas produk kimia sel.

• Memodifikasi protein & lipid & prepares them for exportation.

• Uses sugar nucleotides to transport the proteins.

What else does it do?

• It works with the endoplasmic reticulum.

• It uses a Trans Golgi Network (TGN) to attach chemical “flags” on the exported proteins as sort of an address code so that they get to the right place in the cell.

What’s so Great about it?

• Without the Golgi Apparatus, cells could not secrete important chemicals into our bodies such as:

Hormones (to change us)Enzymes (create

chemical reactions)Antibodies ( keep us

from getting ill and possibly dying)

Lysosomes

• Digestive compartments• Digest macromolecules (protein, as. Nukleat, lipid, KH)• Digest substances ingested by phagocytosis• Membrane-bound sac filled with enzymes• pH 5 maintained by hydrogen ion pump• Manufactured by rough ER and Golgi• Fuse with food vacuoles for digestion• Can fuse with organelle or part of cytosol• Cell renewal; programmed destruction of cells during

development

Lysosomal enzymes

• 50 different degradative enzymes

• Acid hydrolases– Active at pH 5 (inside

lysosome)– Inactive if released into

cytosol (pH 7.2)

• Acidic pH of lysosomes maintained by a proton pump in the lysosomal membrane– Requires ATP

mitochondria

Products delivered to lysosomes by four routes:

• Indiscriminate Pinocytosis– Cell “drinking” < 150nm

• Receptor Mediated Endocytosis

• Phagocytosis– Cell “eating” of material >

250nm• Autophagy

– “self eat” of old worn out organelles,

– important in cell degradation during apoptosis

Lysosomes

Lysosome Lysosome pathwayspathways

Primary lysosomePrimary lysosomeBuds from trans face of GolgiBuds from trans face of Golgiexogenous materials, exogenous materials, deteriorating organellesdeteriorating organelles

Secondary lysosomeSecondary lysosomeprimary fuses with an primary fuses with an endosomeendosome or or phagosomephagosome

Usually look more electron Usually look more electron densedense

Lysosomal enzyme deficiency

Tay Sach’s Disease

• A lysosomal storage disease– Due to a mutation in

lysosomal enzymes

-N-hexosaminidase-A*• Accumulations of un-

degraded glycolipid within lysosomes

• Found in neurons of CNS(central neuro systems)

The formation and functions of lysosomes (Layer 1)

The formation and functions of lysosomes (Layer 2)

The formation and functions of lysosomes (Layer 3)

Review: relationships among organelles of the endomembrane system 

Functions of endomembrane system (summary)

• Manufactures macromolecules and membranes

• Modifies macromolecules for their various functions

• Digests (hydrolyses) macromolecules

Peroxisomes

• Similar structure to lysosomes– Single membrane

• Consume oxygen – but not to form ATP as

mitochondria

• Degrades hydrogen peroxide (H2O2) – can be toxic to cells– Using catalase to degrade

hydrogen peroxide to water

Crystallineinclusion

Peroxisomes

• Consume oxygen in various metabolic functions• Bounded by a single membrane.• Spherical with a granular or crystalline core

thought to be a dense collection of enzyme molecules.

• Not formed by budding from the endomembrane system, but by using proteins and lipids made in the cytosol. Form new peroxisomes by dividing.

Peroxisomes

Peroxisomes (cont.)

• Involved in various metabolic functions, e.g. some break down fatty acids. In the liver, peroxisomes detoxify harmful compounds. Seeds have glyoxysomes.

• Peroxisomes metabolize molecules by transferring hydrogen to oxygen, producing H2O2 – hydrogen peroxide. An enzyme in the peroxisome converts this toxic by-product into water.