3- The Endomembrane System

Transcription

1 B- Eukaryotic Cell

2 3- The Endomembrane System a) The endoplasmic reticulum الشبكة الندوبلزمية manufacturers membranes and performs many other biosynthetic functions b) The Golgi apparatus جولچى, finishesجهاز sorts, and ships cell products c) The Lysosomes areاليسوزومات digestive compartments d) The Vacuoles haveالفجوات diverse functions in cell maintenance

3 A)- The endoplasmic reticulum (ER) manufacturers membranes and performs many other biosynthetic functions The ER includes membranous tubules There are two types of ER that differ in structure and function. 1. Smooth ER looks ناعمةsmooth because it lacks ribosomes. 2. Rough ER looks rough because ribosomes خشنة (bound ribosomes) are attached to its outside. Fig. 7.11, Page 119

4 الشبكة الندوبلزمية الناعمة ER: The smooth - It is rich in enzymes and plays a role in metabolic processes. - Its enzymes synthesize lipids دهون (oils, phospholipids,.الهرمونات الجنسية and steroids) including the sex hormones إبطال الثر السام in the liver, it helps detoxify توجد بكثرة - Extensive السموم and poisons المخدرات drugs الشبكة الندوبلزمية الخشنة ER: The rough - is especially abundant متوفرة in those cells that secrete proteins as it contains ribosomes. - These secretory proteins are packaged in transport vesicles that carry them to their next stage.

5 B)- Golgi apparatus: finishes, sorts,ت<ج:هز packaging and ships تغلف وتنقل cell products Many transport vesicles أوعية ناقلة from the ER travel to the Golgi apparatus for modification تطوير of their contents. The Golgi function is manufacturing,تصنيع warehousing materials to نقل (Packaging), and shipping ت:ج 9 هيز sorting,تغليف outside the cell. The Golgi apparatus is especially extensive in cells.خليا إفرازية specialized for secretion The Golgi also manufactures pectin and polysaccharides.

6 Fig. 7.12, Page 120 وعاء ناقل

7 C)- Lysosomes الجسام الم<حللة are digestive components The lysosome is a membrane-bounded sac ofكيس enzymes that digests macromolecules. Fig. 7.13a, Page 121

8 Lysozomal enzymes Lysosomal enzymes work best at ph = 5 (acidic). The lysosomal enzymes are synthesized by rough ER and then transferred to تنقل إلى the Golgi then to lysosomes. Function of Lysozomal enzymes 1) They hydrolyse, proteinsيحلل fats, polysaccharides, and nucleic acids..الهضم الذاتى (autophagy) 2) Can destroy the cell by autodigestion 3) Can fuse with food vacuoles الفحجوة الغذائية to digest food, (when a food item is brought into the cell by phagocytosis). 4) Can also fuse with another organelle or part of the cytosol. This process of autophagy called recycling which renews the cell

9 Fig. 7.14, Page 122

10 الفجوات Vacuoles: D)- للحفاظ على الخلية inوظائف cell maintenance متنوعة have diverse functions Vesicles أوعية and vacuoles فجوات are membrane-bound sacs أكياس ذات أغشية with varied functions. 1. Food vacuoles غذائية,فجوة from phagocytosis, fuse with lysosomes. 2. Contractile vacuoles فجوة منقبضة, found in freshwater protists, pump excess water out of the cell. 3. Central vacuoles فجوة مركزية are found in many mature plant cells.

11 خلية نباتية الفجوة المركذية خلية حيوانية Figs & 166, Page 123

12 Other Membranous Organelles A)- Peroxisomes contain enzymes that transfer hydrogen from various substrates to oxygen. Functions of peroxisomes 1- Hydrogen peroxide (H2O2) is a poison, but the peroxisome has enzyme that converts H2O2 to water. 2- Some peroxisomes break fatty acids down to smaller molecules that are transported to.لنتاج الطاقة mitochondria for fuel 3- They detoxify يبطل المفعول السXمى alcohol and other harmful compounds. Thus, it exists extensively in the liver cells

13 Other Membranous Organelles B)- Mitochondria: Thy are the main energy transformers of cells as they convert energy to fuel الطاقة that cells can use for work. Mitochondria are the sites of cellular respiration, generating ت<نت\ج ATP from the catabolism هدم of sugars, fats, and other fuels طاقة مصادر in the presence of oxygen. Almost all eukaryotic cells have mitochondria. Mitochondria and chloroplasts are mobile and move around the cell along tracks in the cytoskeleton.

14 Mitochondria have a smooth outer membrane and a highly folded.نتوءات inner membrane forming cristae The inner membrane encloses the mitochondrial matrix, a fluid-filled space with DNA, ribosomes, and enzymes. Fig. 7.17, Page 124