بسم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم ﴿و ما أوتيتم من العلم إلا قليلا﴾ صدق الله العظيم الاسراء اية 58

2. BIOPHYSICS By Dr. Abdel Aziz M. Hussein Lecturer of Medical Physiology Member of American Society of Physiology

3. Cell Physiology

4. Biophysics , Abdelaziz Hussein

8. Cell Membrane

9. Cell Membrane 7.5 nm Z A B F

10. Cell Membrane Def. • It is a very thin elastic semi-permeable membrane (allowing some substances to pass through it and prevent others) that surrounds the cell Thickness: • It is about 7.5 nm (75 Ao = Angstrom = 10-10 of meter) in thickness. Biophysics , Abdelaziz Hussein

11. Cell Membrane Functions

12. Functions of Cell Membrane • Separates the cytoplasm from ECF. • Maintains cell's internal environment. ECF ICF or cytoplasm Cell environment Biophysics , Abdelaziz Hussein

13. Functions of Cell Membrane 3. Controls distribution of ions e.g. Na, K in ICF and ECF. 4. Transports of macromolecules into and out of the cell. Biophysics , Abdelaziz Hussein

14. Functions of Cell Membrane 5. Generates transmembrane potentials. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ +++++++++++++++++++++++ Biophysics , Abdelaziz Hussein

15. Functions of Cell Membrane 6. Contains receptors for hormones and transmitter substances. 7. Important for signal transduction Biophysics , Abdelaziz Hussein

16. Structure of Cell Membrane

18. Components of Cell Membrane • It is formed of 3 components; Biophysics , Abdelaziz Hussein

19. Cell Membrane Lipids

20. Cell Membrane Lipids Biophysics , Abdelaziz Hussein

21. Cell Membrane Lipids • The basic structure of cell membrane • 3 types: • Phospholipids • Cholesterol • Glycolipids Biophysics , Abdelaziz Hussein

22. Cell Membrane phospholipids

23. Cell Membrane phospholipids • Arranged into 2 layers (Lipid bilayer) • Phospholipids molecules resemble the clothes-pin shape • Consist of; • Head (PO4 group) (face the ICF and ECF sides) relatively H2O soluble (polar, hydrophilic). • Tails (face each other in the interior of the bilayer) → relatively H2O insoluble (non-polar, hydrophobic). Biophysics , Abdelaziz Hussein

25. Cell Membrane Proteins

26. Cell Membrane Proteins Biophysics , Abdelaziz Hussein

27. Types of Cell Membrane proteins Integral or intrinsic proteins→ bind to hydrophobic center of the lipid bilayer Peripheral or extrinsic proteins→ bind to the hydrophilic polar heads of the lipids or to the integral proteins Biophysics , Abdelaziz Hussein

28. Integral Cell Membrane Proteins Integral cell membrane proteins are 2 types; Transmembrane proteins → span the entire bilayer Present on one side Biophysics , Abdelaziz Hussein

29. Functions of transmembrane Proteins Act as; a. Channels → for diffusion of small, water–soluble substances. b. Carriers actively transport materials across the bilayer. c. Pumps actively transport ions across the bilayer. d.Receptors : initiate intracellular reactions when activated. Biophysics , Abdelaziz Hussein

30. Functions of integral Proteins on one side • Act as enzymes that activate or inactive metabolic processes. Biophysics , Abdelaziz Hussein

31. Functions of Peripheral Proteins

32. Functions of Peripheral Proteins Peripheral protein may be: i) Peripheral proteins: bind to the intracellular surface of the membrane and contribute to the cytoskeleton. ii) Peripheral proteins: bind to the extracellular surface of the membrane and contribute to the glycocalyx. Biophysics , Abdelaziz Hussein

33. Functions of Glycocalyx • It is composed of glycolipids and glycoproteins and covers the cell membrane. • -It is -vely charged Biophysics , Abdelaziz Hussein

34. Functions of Glycocalyx • Functions • It binds to the extracellular Ca to stabilize membrane structures. • It acts as an attachment matrix for other cells (cell adhesion molecules). • 3. Forms antigens of blood groups on RBCs Biophysics , Abdelaziz Hussein

36. Intercellular Connections Biophysics , Abdelaziz Hussein

37. Biophysics , Abdelaziz Hussein

38. Intercellular Connections • 2 types of intercellular connections • A) Tight junctions • Are attachments between cells at their apical borders • B) Gap junctions • Are attachments between cells that permit intercellular communications Biophysics , Abdelaziz Hussein

39. Tight Junctions • At the junction→ the adjacent cell membranes are fused at ridges projecting from adjacent cells • Present in epithelial cells of; Gall bladder. Renal proximal and distal tubules Biophysics , Abdelaziz Hussein

40. Tight Junctions • Functions • They are intercellular pathways for solutes and water. • Types • They may be; • i)Tight(impermeable to solutes and H2O) as in the renal distal tubule. • ii)Leaky (permeable) as in the renal proximal tubule or gall bladder Biophysics , Abdelaziz Hussein

41. Gap Junctions • Present in Cardiac ms, smooth ms, and epithelial cells. • Not present in neuron or skeletal ms. -They are highly non selective channels allowing all ions and macromolecules to pass. -They consist of 6 similar subunits called connexins on each cell. -Each set (connexon) of subunits is arranged to form a common pore. Biophysics , Abdelaziz Hussein

42. Gap Junctions i) In cardiac and smooth ms→ provide a low resistance path for the spread of ionic currents. ii) In other cells → facilitate the passage of metabolites and intercellular signals between cells. Biophysics , Abdelaziz Hussein

47. THANKS