1 The Cell Organelles عضيــات الخليـــــــــة

2 The nucleus contains most of the genes in an eukaryotic cell.The nucleus contains most of the genes in an eukaryotic cell. The nucleus is separated from the cytoplasm by a double membrane غشاء مزدوج called nuclear membrane.The nucleus is separated from the cytoplasm by a double membrane غشاء مزدوج called nuclear membrane. The nuclear membrane contains pores ثقوب that allow large macromolecules and particles to pass through.The nuclear membrane contains pores ثقوب that allow large macromolecules and particles to pass through. The nuclear membrane الغلاف النووى is maintaining the shape of the nucleusThe nuclear membrane الغلاف النووى is maintaining the shape of the nucleus 1. The nucleus: Contains the cell’s genetic library المحتوى الـﭽينى

3 Fig. 7.9, Page 116

4 chromatinWithin the nucleus, the DNA and associated proteins are organized into fibrous material, chromatin. In a normal cell they appear as diffuse mass. chromosomes However when the cell prepares to divide, the chromatin fibers coil up تلتف to be seen as separate structures, chromosomes. Each eukaryotic species has a characteristic number of chromosomes رقم مُمَيـٍز من الكروموسومات. - A typical human cell has 46 chromosomes, but sex cells (eggs and sperm) have only 23 chromosomes. Nucleolus is a dark region involved in production of ribosomes. The nucleus directs protein synthesis by synthesizing messenger RNA (mRNA). –The mRNA travels to the cytoplasm and combines with ribosomes to translate its genetic message into the primary structure of a specific polypeptide.

5 Ribosomes contain rRNA and protein. A ribosome is composed of two subunits وحدتين that combine تتحد to carry out protein synthesis. 2. Ribosomes :Build a cell’s proteins Fig. 7.10, Page 117 مرتبطة حرة

6 In the nucleolus, ribosomal RNA (rRNA) is synthesized and assembled with proteins from the cytoplasm to form ribosomal subunits.In the nucleolus, ribosomal RNA (rRNA) is synthesized and assembled with proteins from the cytoplasm to form ribosomal subunits. The subunits pass from the nuclear pores to the cytoplasm where they combine to form ribosomes.The subunits pass from the nuclear pores to the cytoplasm where they combine to form ribosomes. Cell types that synthesize large quantities of proteins (e.g., pancreas) have large numbers of ribosomes.Cell types that synthesize large quantities of proteins (e.g., pancreas) have large numbers of ribosomes. Ribosomes are 2 types:-Ribosomes are 2 types:- 1.Free ribosomes 1.Free ribosomes are suspended معلق in the cytosol and synthesize proteins that function within the cytosol. 2.Bound ribosomes are attached to ملتصق بـ the outside of the endoplasmic reticulum. –These synthesize proteins that are either included into membranes or for export from the cell.

B- Eukaryotic Cell

3- The Endomembrane System a)The endoplasmic reticulum الشبكة الإندوبلازمية manufacturers membranes and performs many other biosynthetic functions b)The Golgi apparatus جهاز جولـﭽـى finishes, sorts, and ships cell products c)The Lysosomes اليسوزومات are digestive compartments d) The Vacuoles الفجوات have diverse functions in cell maintenance

9 Fig. 7.11, Page 119 A)- The endoplasmic reticulum manufacturers membranes and performs many other biosynthetic functions ERThe ER includes membranous tubules ERThere are two types of ER that differ in structure and function. 1.Smooth ER 1.Smooth ER looks smooth because it lacks ribosomes. 2.Rough ER 2.Rough ER looks rough because ribosomes (bound ribosomes) are attached to the outside, including the outside of the nuclear envelope.

The smooth ER:The smooth ER: الشبكة الإندوبلازمية الناعمة - It is rich in enzymes and plays a role in metabolic processes. الهرمونات الجنسية - Its enzymes synthesize lipids دهون (oils, phospholipids, and steroids) including the sex hormones الهرمونات الجنسية. توجد بكثرةإبطال الأثر السام المخدراتالسموم - Extensive توجد بكثرة in the liver, it helps detoxify إبطال الأثر السام drugs المخدرات and poisons السموم The rough ER:The rough ER: الشبكة الإندوبلازمية الخشنة متوفرة - 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.

11 Many transport vesicles أوعية ناقلة from the ER travel to the Golgi apparatus for modification تطوير of their contents. The Golgi is a center of manufacturing تصنيع, warehousing تغليف, sorting تـُجَهيز ( packaging), and shipping نقل materals to outside the cell. specialized for secretionThe Golgi apparatus is especially extensive in cells specialized for secretion خلايا إفرازية. The Golgi also manufactures pectin and polysaccharides. B)- The Golgi apparatus: finishes, sorts تـُجَهز, and ships تنقل cell products

12 Fig. 7.12, Page 120 وعاء ناقل

13 lysosomeThe lysosome is a membrane-bounded sac of enzymes that digests macromolecules. C)- Lysosomes الأجسام المُحللة are digestive components Fig. 7.13a, Page 121

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 يحلل proteins, fats, polysaccharides, and nucleic acids. الهضم الذاتى 2)Can destroy the cell by autodigestion (autophagy) الهضم الذاتى. الفحجوة الغذائية 3)Can fuse with food vacuoles الفحجوة الغذائية to digest food, (when a food item is brought into the cell by phagocytosis). recycling 4)Can also fuse with another organelle or part of the cytosol. This process of autophagy called recycling which renews the cell Lysozomal enzymes

15 Fig. 7.14, Page 122

16 Vesicles أوعـية and vacuoles فجوات are membrane- bound sacs أكياس with varied functions. 1.Food vacuoles 1.Food vacuoles, from phagocytosis, fuse with lysosomes. 2.Contractile vacuoles 2.Contractile vacuoles, found in freshwater protists, pump excess water out of the cell. 3.Central vacuoles 3.Central vacuoles are found in many mature plant cells. D)- Vacuoles الفجوات: Have diverse functions وظائف متنوعة in cell maintenance للحفاظ على الخلية

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

18 The membrane surrounding the central vacuole, the tonoplast, is selective إختيارى النفازية in its transport of materials into the central vacuole. The functions of the central vacuole include storing proteins or inorganic ions, depositing metabolic byproducts ترسيب نواتج الأيض الثانوية, storing pigments الأصباغ تخزين. It also increases internal surface of the cell.

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

20 Mitochondria and chloroplasts are the organelles that convert energy to forms that cells can use for work. MitochondriaATPMitochondria are the sites of cellular respiration, generating تـُنتِج ATP from the catabolism هدم of sugars, fats, and other fuels مصادر طاقة in the presence of oxygen. ChloroplastsChloroplasts, found in plants and eukaryotic algae طحالب, are the site of photosynthesis. - They convert solar energy تحول الطاقة الشمسية to chemical energy and synthesize new organic compounds from CO 2 and H 2 O. Mitochondria and chloroplasts are not part of the endomembrane system. Almost all eukaryotic cells have mitochondria. Mitochondria and chloroplasts are mobile and move around the cell along tracks in the cytoskeleton. Mitochondria: Mitochondria and chloroplasts are the main energy transformers of cells B)- Mitochondria: Mitochondria and chloroplasts are the main energy transformers of cells

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

22 The chloroplastThe chloroplast produces sugar via photosynthesis. chlorophyll –Chloroplasts gain their color from high levels of the green pigment chlorophyll. Chloroplasts measure about 2 microns x 5 microns and are found in leaves and other green structures of plants and in eukaryotic algae. Fig. 7.18, Page 125

23 The processes in the chloroplast are separated from the cytosol by two membranes. Inside the innermost membrane is a fluid-filled space, the stroma, in which float membranous sacs, the thylakoids. –The stroma contains DNA, ribosomes, and enzymes for part of photosynthesis. –The thylakoids, flattened sacs, are stacked into grana and are critical for converting light to chemical energy.

24 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 7.18