1. صدق الله العظيم الاسراء اية 58

2. By Dr. Abdel Aziz M. Hussein Lecturer of Medical Physiology

3. Organization of Human Body The human body is made up of different systems e.g. digestive system, whose functions are coordinated and integrated together. Each system consists of many organs that made up of many tissues of complementary functions. Each tissue consists of millions of similar cells. The cell is the basic unit of structure and function in the body Each animal cell is surrounded by a cell membrane Abdelaziz Hussein 3

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5. Cell (Plasma) MembraneCell (Plasma) Membrane 5 Abdelaziz Hussein

6. Cell Membrane It is a very thin elastic semi-permeable membrane (allowing some substances to pass through it and prevent others) that surrounds the cell It is about 7.5 nm (75 A o = Angstrom = 10 -10 of meter) in thickness. 6 Abdelaziz Hussein

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8. Functions of Cell Membrane 1.It separates the cytoplasm from ECF. 2.It maintains cell's internal environment. 3.It transports of macromolecules into and out of the cell. 4.It controls distribution of ions e.g. Na, K extracellular ICF and ECF. 5.It generates transmembrane potentials. 6.It is contains receptors for hormones and transmitter substances which are important for signal transduction 8 Biophysics, Abdelaziz Hussein

9. Components of Cell Membrane It is formed of 3 components; 1.Lipids 42%. 2.Proteins 55%. 3.Carbohydrates 3%. 9 Abdelaziz Hussein

10. Cell Membrane Lipids 10 Abdelaziz Hussein

11. Cell Membrane Lipids 11 Abdelaziz Hussein Form the basic structure of the membrane. Include mainly phospholipids, cholesterol, and glycolipids. Phospholipids are arranged into 2 layers (Lipid bilayer) Phospholipids molecules resemble the clothes-pin shape It 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).

12. Cell Membrane Proteins 12 Abdelaziz Hussein

13. Functions of Cell Membrane Integral Proteins 13 Abdelaziz Hussein 1.Integral or intrinsic proteins→ 1.Integral or intrinsic proteins→bind to hydrophobic center of the lipid bilayer 2.Peripheral or extrinsic proteins 2.Peripheral or extrinsic proteins → bind to the hydrophilic polar heads of the lipids or to the integral proteins

14. Functions of Cell Membrane Integral Proteins 14 Abdelaziz Hussein i)Transmembrane proteins i)Transmembrane proteins → span the entire bilayer which 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.

15. Functions of Cell Membrane Integral Proteins 15 Abdelaziz Hussein ii)Present only on one side of the membrane They act as enzymes that activate or inactive metabolic processes.

16. Functions of Cell Membrane Peripheral Proteins 16 Biophysics, Abdelaziz Hussein The peripheral protein may be: i) Peripheral proteins: i) Peripheral proteins: bind to the intracellular surface of the membrane and contribute to the cytoskeleton. ii) Peripheral proteins: ii) Peripheral proteins: bind to the extracellular surface of the membrane and contribute to the glycocalyx.

17. Glycocalyx 17 Abdelaziz Hussein 2. It acts as an attachment matrix for other cells (cell adhesion molecules). It is composed of glycolipids and glycoproteins and covers the cell membrane. Functions Functions 1. 1. It binds to the extracellular Ca to stabilize membrane structures.

18. Transport through the Cell Membrane 18 Abdelaziz Hussein

19. Transport through the Cell MembraneTransport through the Cell Membrane 19 Abdelaziz Hussein

20. Transport through the Cell MembraneTransport through the Cell Membrane 20 Abdelaziz Hussein There are 3 mechanisms for transport of substances through cell membranes; a) Passive transport (Diffusion): It is movement of substances across the cell membrane down its electrochemical gradient. b) Active transport: It is movement of substances across the cell membrane against its electrochemical gradient. c) Vesicular transport: It is the process by which large sized substances are engulfed by the cell membrane to be either pushed inside the cell (endocytosis) or pushed outside the cell (exocytosis)

21. Diffusion 21 Abdelaziz Hussein It is divided into 3 subtypes: 1.Simple diffusion. 2.Facilitated diffusion. 3.Osmosis (water only)

22. Simple DiffusionSimple Diffusion 22 Abdelaziz Hussein It is movement of substances across the cell membrane down its electrochemical gradient by simple movement without the necessity of binding with carrier proteins Mechanisms: It occurs either through; The interstices of the lipid bilayer. The watery proteins channels.

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24. Simple DiffusionSimple Diffusion 24 Abdelaziz Hussein Characters: It is characterized by; a) It occurs down an electro- chemical gradient. b) It is passive i.e. no external energy is required.

25. Simple DiffusionSimple Diffusion 25 Abdelaziz Hussein Characters: It is characterized by; c) It is not rate-limiting i.e. linear with concentration gradients. d) The diffusion process is not saturable.

26. Osmosis or Diffusion of WaterOsmosis or Diffusion of Water 26 Abdelaziz Hussein Water diffuses through lipid bilayer of the membrane at high rate like bullets due to; Its small size. Its very high kinetic energy Water moves from high to low concentrations of water

27. Facilitated DiffusionFacilitated Diffusion 27 Abdelaziz Hussein It is the diffusion of substances across the cell membrane (down electrochemical gradient) which needs the presence of carrier proteins→ carrier mediated diffusion Characters i) It occurs down an electrochemical gradient ii) It is passive i.e. no energy is required. iii) It requires the presence of a transport carrier protein. iv) It is rate-limiting and saturable because it depends on the availability of a definite number of carrier or channel proteins

28. II) Active Transport 28 Abdelaziz Hussein Def., It is the movement of substances across the cell membranes against an electrochemical gradient. Types: There are 2 subtypes of active transport: i) Primary active transport → obtain its energy directly from the hydrolysis of ATP e.g. Na-K Pump, Ca ATPase, H-K ATPase ii) Secondary active transport → use the energy stored in the Na concentration gradient e.g. Na-glucose co-transport and Na-Ca exchange

29. II) Active Transport 29 Abdelaziz Hussein Characters 1. It occurs against the electrochemical gradient 2. It is active i.e. energy is required 3. It requires the presence of a transport carrier protein 4. It exhibits stereospecificity, saturation, and competition

30. 1ry Active Transport 30 Abdelaziz Hussein (Na-K ATPase) Na-K pump Ca-ATPase (Ca-pump) K-H-ATPase (proton pump) Site It presents in the cell membranes. It is present in sarcoplasmic reticulum and cell membranes. It presents in stomach parietal- cells and renal distal tubular cells. Importancemaintains low intracellular Na and high intracellular K. It maintains the intracellular Ca ions concentration low. It transports H ions into the lumen against its electrochemical gradient.

31. 2ry Active Transport 31 Abdelaziz Hussein Na-glucose co- transport Na-Ca Exchange Site It presents in the cell membranes. It is present in ventricular ms cells Importance Transport of Na & glucose into the cells It transports Ca uphill from low ICF Ca to high ECF Ca

32. Differences ( ) simple diffusion, facilitated diffusion and active transport 32 Abdelaziz Hussein Simple diffusionFacilitated diffusionActive transport Electrochemical gradient Downhill Uphill Energy Doenot need energy Needs energy Rate Not limitedLimited Saturation Not SaturableSaturable Carrier Doenot need carrierNeeds carrier Competition Not show competitionShows competition

33. III) Vesicular Transport 33 Abdelaziz Hussein It is the mechanism by which the large sized substances can cross the cell membranes a) Endocytosis It is active process which uses energy The extracellular material is trapped within vesicles that are formed by invagination of the cell membrane It is 3 types

34. III) Vesicular Transport 34 Abdelaziz Hussein a) Exocytosis It is active process which uses energy The intracellular material is trapped within vesicles, then the vesicles fuse with the cell membrane and release their contents to the ECF e.g. release of hormones, digestive enzymes, and synaptic transmitters

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