1 CHAPTER 8 MEMBRANE STUCTURE AND FUNCTION How things get into and out of the cell Active Transport النقل النشط

2 This active transport requires metabolic energy via ATP.This active transport requires metabolic energy via ATP. Active transport is the pumping of solutes against their concentration gradients عكس Active transport is the pumping ضَخ of solutes against their concentration gradients عكس الإنحدار التركيزى Fig. 8.14b, Page 148 Active transport is critical بالغ الأهمية for a cell to maintainتحافظ its internal concentrations التركيزات الداخليةof small molecules. Active transport is performed يتم by specific proteins embedded موجودةin the membranes (transport protein).

3 The sodium-potassium pump مضخة الصوديوم والبوتاسيومactively maintains the gradient of sodium (Na + ) and potassium ions (K + ) in the cell.The sodium-potassium pump مضخة الصوديوم والبوتاسيومactively maintains the gradient of sodium (Na + ) and potassium ions (K + ) in the cell. –The sodium-potassium pump uses the energy الطاقةof one ATP to pump 3 Na + ions out and 2 K + ions in. 1)- Small molecules Ions) 1)- Small molecules (Ions ) High conc. of K + High conc. of Na + Low conc. of K + Low conc. of Na + 1ATP 3 2 T. protein Na Cellular membrane Protein molecule Inside the cell Outside the cell ATP Na Na Na Na Na Na

4 Fig. 8.15, Page 149

5 down their concentration gradient against their concentration gradient Fig. 8.16, Page 150 Both diffusion and facilitated diffusion are forms of passive transport of molecules down their concentration gradient, while active transport requires an investment of energy to move molecules against their concentration gradient. Two roles of membrane protein

6  Large molecules, such as polysaccharides السكريات العديدةand proteins, cross the membrane by vesicles.  Large molecules, such as polysaccharides السكريات العديدةand proteins, cross the membrane by vesicles أوعية. 1.Exocytosis الإخراج الخلوي: A vesicle is budded from ينشأ من the Golgi apparatus is moved by the cytoskeleton to the plasma membrane. A vesicle is budded from ينشأ من the Golgi apparatus is moved by the cytoskeleton to the plasma membrane. When the vesicle and plasma membrane come in contact تلامس, they fuse يندمج and spill يُفرغ the contents المحتوى to the outside. When the vesicle and plasma membrane come in contact تلامس, they fuse يندمج and spill يُفرغ the contents المحتوى to the outside. Endocytosis الإدخال الخلوى a cell brings in macromolecules by forming new vesicles from the plasma membrane and include the following: 2- Endocytosis الإدخال الخلوى, a cell brings in macromolecules by forming new vesicles from the plasma membrane and include the following: Large molecules are transported by Exocytosis and endocytosis 2)- Large molecules ()الجزيئات الكبيرة 2)- Large molecules ( macromolecules )الجزيئات الكبيرة

7 Fig. 8.19a, Page 152 A)- Phagocytosis الإبتلاع : A)- Phagocytosis الإبتلاع الخلوى : Called “cellular eating”. The cell engulfs a particle by extending pseudopodia أقدام كاذبة around it and packaging it تـُغلفها in a large vacuole. Called “cellular eating”. The cell engulfs تـَبْلَع a particle by extending pseudopodia أقدام كاذبة around it and packaging it تـُغلفها in a large vacuole.

8 B)- Pinocytosis, “cellular drinking”, B)- Pinocytosis, الشرب الخلوى “cellular drinking”, A cell creates a vesicle around droplets نقاط of extracellular fluid السائل الموجود خارج الخلية. A cell creates a vesicle around droplets نقاط of extracellular fluid السائل الموجود خارج الخلية. Fig. 8.19b, Page 152

9 C)- Receptor-mediated endocytosis: C)- Receptor-mediated endocytosis: الإدخال الخلوى عن طريق المستقبلات المتخصصة It is triggered تـُستـَحث when extracellular substances bind to special receptors مُستقبـِلات خاصة, on the membrane surface. This triggers the formation of a vesicle وعاءIt is triggered تـُستـَحث when extracellular substances bind to special receptors مُستقبـِلات خاصة, on the membrane surface. This triggers the formation of a vesicle وعاء It enables تسمح للخليةa cell to take large quantitiesكميات كبيرة of specific materials that may be in low concentrations تركيز قليل in the environmentالبيئة.It enables تسمح للخليةa cell to take large quantitiesكميات كبيرة of specific materials that may be in low concentrations تركيز قليل in the environmentالبيئة. Fig. 8.19c, Page 152

10 Phagocytosis PinocytosisReceptor-mediatedendocytosis Cellular eating Cellular drinking Selective eating Transport PassiveActive DiffusionFacilitateddiffusion LargemoleculesSmallMolecules/ions (T. protein) (Membrane) (Membrane) ExocytosisEndocytosis