CHAPTER 5 THE STRUCTURE AND FUNCTION OF MACROMOLECULES MEMBRANE STUCTURE AND FUNCTION

 This barrier حاجز, 8 nm thick, controls entrance دخول into and exit خروج out of the cell.  The plasma membrane is selectively permeable مُنفِذ اختياريا, allowing some substances to pass تمر more easily than others.  Plasma membrane is composed of two layers of Phospholipids and different types of proteins Section A: Membrane Structure (Introduction)

Peripheral proteins Integral proteins Types of membrane proteins أنواع البروتينات في غشاء الخلية There are two types نوعان of membrane proteins.There are two types نوعان of membrane proteins. 1.Peripheral proteins البروتين الطرفي They are not embedded in the lipid bilayer ليست مخترقة لطبقة الدهون. 2. Integral proteins البروتين المندمج penetrate تخترق the hydrophobic part of the lipid bilayer. Fig. 8.7, Page 143

The proteins in the plasma membrane may provide a variety of major cell functions.The proteins in the plasma membrane may provide a variety of major cell functions. Fig. 8.9, Page 144 النقل يعمل كإنزيم نقل الإشارات الربط بين الخلايا التعارف بين الخلايا الربط مع هيكل الخلايا وخارجها

How can materials enter or exit via plasma membrane?

Diffusion: الانتشارDiffusion: الانتشار Is the tendency استعداد of molecules to spread out للانتشار in the available space. Is the tendency استعداد of molecules to spread out للانتشار in the available space. 1- Passive transport It means diffusion الانتشار across خلال plasma membrane 1- Passive transport الانتقال السلبى It means diffusion الانتشار across خلال plasma membrane Fig. 8.10a, Page 145 صبغة

Fig. 8.10b, Page 145 CD Unit 2, Chapter 8. Passive transport: الإنتقال السلبى Passive transport: الإنتقال السلبى Diffusion of substance انتشار مادة from where it is more concentrated to where it is less concentrated من التركيز الاعلي للأقل, down its concentration gradient. Diffusion of substance انتشار مادة from where it is more concentrated to where it is less concentrated من التركيز الاعلي للأقل, down its concentration gradient مـُنحدر التركيز. It requires no energy لا يحتاج لطاقة

The solution with the higher concentration of solutes is hypertonic.The solution with the higher concentration of solutes is hypertonic. The solution with the lower concentration of solutes is hypotonic.The solution with the lower concentration of solutes is hypotonic. Solutions with equal solute concentrations are isotonic.Solutions with equal solute concentrations are isotonic.Osmosis: Is a passive transport in which water diffuses from the hypotonic solution to the hypertonic solution until the solutions become isotonic. Is a passive transport in which water diffuses from the hypotonic solution to the hypertonic solution until the solutions become isotonic. Osmosis الأسموزية : is the passive transport of water Fig. 8.11, page 146

Passive transport of water () Passive transport of water ( Osmosis ) Hypertonic solution: contains high concentration of solute مُذاب molecules.Hypertonic solution: عالى التركيز contains high concentration of solute مُذاب molecules. Hypotonic solution: contains low concentration of solute molecules.Hypotonic solution: منخفض التركيز contains low concentration of solute molecules. Isotonic solution: contains equal concentrations of solute moleculesIsotonic solution: متعادل contains equal concentrations of solute molecules Biological MembraneHypotonicHypertonic H2OH2OH2OH2O

Definition تعريف of facilitated diffusion The passive movement of molecules from high concentration to low concentration via a transport proteins البروتينات الناقلة (gated channels ).The passive movement of molecules from high concentration to low concentration via a transport proteins البروتينات الناقلة (gated channels قنوات مُبَوبة ). 2. Facilitated diffusion