Copy1-Cell_Physiology_2_Illustrated_Presentation.pptx

cell physiology

1. Cell Physiology 2 Ashur university - College of Medicine 202 5 -202 6 Dr. Tiba Akram 2 nd stage

2. Introduction How the particles transport across cell membrane between ICF and ECF ?

3. Primary active transport is a type of membrane transport where substances (ions or molecules) are moved across a biological membrane against their concentration or electrochemical gradient using energy directly obtained from the hydrolysis of ATP. Primary active transport

4. Na⁺-K⁺ Pump Function: Maintains resting membrane potential 2. Maintains cell volume and prevents swelling. Mechanism: Pumps 3 Na⁺ out and 2 K⁺ in per ATP.

5. Why cell volume needs to be controlled? • Inside cells, there are lots of negatively charged proteins and other solutes. These attract cations (especially Na⁺), which would osmotically pull water into the cell. Without regulation, the cell would swell and burst.

6. How this controls volume? 1. Removes Na⁺ (main osmotically active ion): Pumping Na⁺ out lowers the intracellular osmolarity → reduces water entery and prevent swelling 2. Maintains osmotic balance: Since fewer positive ions are kept inside, the intracellular solute concentration is controlled. → Prevents swelling. 3. Indirect effect via K⁺: Although K⁺ enters, many K⁺ leak back out through K⁺ channels. This prevents K⁺ buildup, so no excess osmotic load is created.

7. “Na⁺ out = water out.”

8. Primary Active Transport of H⁺ Ions Sites: stomach: Gastric parietal cells kidney : late distal tubules and cortical collecting ducts of the kidneys.

9. Kidney: Secretes H⁺ into tubular fluid → eliminates acid, regulates pH.

10. Ca²⁺ Pump Location : Plasma membrane & membrane of endoplasmic reticulum (essential for muscle relaxation) Mechanism Pumps Ca²⁺ out of cytoplasm into ECF or ER. ATP-driven, involves phosphorylation cycle , (primary active transport ) Keeps cytoplasmic Ca²⁺ very low → ready for rapid influx.

11. Secondary active transport is the movement of substances across a membrane against their concentration gradient, but without directly using ATP. One substance moves down its gradient (providing energy), while another moves against its gradient. forms of Secondary Active Transport: 1. co transport : Both molecules move in the same direction. 2. countertransport : Molecules move in opposite directions.

12. Sodium co-transport of glucose and amino acid This is a secondary active transport mechanism that occurs mainly in the intestine and renal tubules of kidneys to promote absorption of these substances into the blood.

13. sodium Counter-Transport of calcium - This is a secondary active transport mechanism that o ccurs in most cells. sodium and calcium bind to carrier protein - Na⁺ enters and energy released cause Ca²⁺ exits

14. sodium Counter-Transport of hydrogen ions Occurs in proximal renal tubules. Na⁺ enters cell from lumen while H⁺ moves into lumen. Role: Assists in H⁺ excretion and Na⁺ reabsorption. Weaker than primary H⁺ pump in distal tubules.

15. Bulk Transport The term bulk is used because many molecules are moved at the same time which molecules? Polypeptides and proteins, as well as many other molecules, which are too large to be transported through a membrane by the carriers.

16. Exocytosis: Vesicles ( Golgi complex ) fuse with plasma membrane → release products (e.g., neurotransmitters from nerve endings ). - Endocytosis: Cell engulfs extracellular material into vesicles.

17. Cholesterol is removed from the blood by the liver and by the walls of blood vessels through this mechanism Absorption of nutrients in the small intestine Defense against microbes, removal of dead cells.

18. - Cells: Neutrophils & macrophages (‘big eaters’). - Functions: Defense against microbes, removal of dead cells.

19. Apoptosis is a normal, ongoing activity in the body and is not accompanied by inflammation

20. Q- The Ca²■ pump in the sarcoplasmic reticulum is activated when: a) ATP binds directly to Ca² channels b) Ca² binds to a cytoplasmic site, stimulating ATP hydrolysis c) Na influx increases d) The Golgi complex provides phosphate groups

21. Q- Which process represents receptor-mediated endocytosis, rather than pinocytosis? a) Engulfment of extracellular fluid with random proteins b) Ingestion of bacteria by macrophages c) Uptake of cholesterol bound to specific transport proteins d) Fusion of neurotransmitter vesicles with plasma membrane