B- Eukaryotic Cell 1 Internal membranes ‫ أغشية داخلية‬compartmentalize ‫ تحدد أعضاء وظيفية‬the functions of a eukaryotic cell • • • • An eukaryotic cell has internal membranes, which partition ‫ تـقـســم‬the cell into compartments ‫أعضاء وظيفية‬. These membranes also participate in metabolism as many enzymes are built into membranes. The general structure of a biological membrane is a double layer ‫ثنائى الطبقات‬ of phospholipids and diverse proteins ‫بروتينات متنوعة‬. Each type of membrane has a unique combination ‫ تركيب مـمـيـ!ز‬of lipids and proteins for its specific functions. – Page 114 For example, those in the membranes of mitochondria function in cellular respiration. 2 B- Eukaryotic Cell Eu: True Karyon: Nucleus Animal Cell Plant Cell What are the functions of cell organelles ? Compare between Animal and Plant cell? Page 114 - 115 3 ‫المادة الوراثية‬ ‫النواة‬ ‫الشبكة الندوبلزمية‬ ‫نوية‬ ‫الجدار النووى‬ ‫سوط حركى‬ ‫جسم مركزى‬ ‫ريبوسوم‬ ‫حهاز جولـﭽـى‬ ‫غشاء بلزمى‬ ‫حلمات دقيقة‬ ‫ميتوكوندريا‬ ‫جسم ‪J‬محلل‬ ‫‪4‬‬ ‫الهيكل الخلوى‬ ‫‪Fig. 7.7, Page 114‬‬ ‫فجوة مركزية‬ ‫بلستيدة خضراء‬ ‫الجدار الخلوى‬ ‫ثقوب بينية‬ ‫‪5‬‬ ‫‪Fig. 7.8, Page 115‬‬ ‫‪The Cell Organelles‬‬ ‫عضيــات‬ ‫الخليـــــــــة‬ ‫‪6‬‬ 1. The nucleus: Contains the cell’s genetic library ‫المحتوى الـﭽينى‬ • • • • The nucleus contains most of the genes in an eukaryotic cell. The nucleus is separated from the cytoplasm by a double membrane ‫ غشاء مزدوج‬called nuclear membrane. The nuclear membrane contains pores ‫ ثقوب‬that allow large macromolecules and particles to pass through. The nuclear membrane ‫ الغلف النووى‬is maintaining the shape of the nucleus 7 Fig. 7.9, Page 116 8 • • • The nucleus contains “chromatin fiber” ‫الخيوط الكروماتينية‬ which is the DNA associated with proteins. When the cell prepares to divide, the chromatin fibers coil up ‫ تلتف‬to be seen as “chromosomes”. Each eukaryotic species has a characteristic number of chromosomes ‫رقم مميـ!ز من الكروموسومات‬. - A typical human cell has 46 chromosomes, but sex cells (eggs and sperm) have only 23 chromosomes. • • 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 protein. Nucleolus is a dark region involved in production of 9 ribosomes. 2. Ribosomes: • • build the cell’s proteins Ribosomes contain rRNA and protein. A ribosome is composed of two subunits ‫ وحدتين‬that combine ‫ تتحد‬to carry out protein synthesis ‫تخليق البروتين‬. ‫حرة‬ ‫مرتبطة‬ Fig. 7.10, Page 117 10 • • • 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. Cell types that synthesize large quantities of proteins (e.g., pancreas) have large numbers of ribosomes. • Types of Ribosomes:- 1) Free ribosomes are suspended ‫ معلق‬in the cytosol and synthesize proteins that function within the cytosol. 2) Bound ribosomes are attached to ‫ ملتصق بـ‬the outside of the endoplasmic reticulum. – These synthesize proteins that are either included into membranes or for secretion outside the cell. 11