PHYSIOLOGY CELL PART 2

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3. Comparison of Animal cell with Precellular Forms of life

5. Functional systems of the cell The following are the important functions of cell that make it a living thing. 1-Ingestion by the cell-Endocytosis Includes:- 1-Pinocytosis 2-Phagocytosis 2-Digestion by lysosomes

6. 3-Excretion (Exocytosis) 4-Synthesis: a)RER (protein synthesis) b)SER (Lipid synthesis) c)Golgi apparatus (Galactose, Hyaluronic acid)

7. 5-Energy Extraction by Mitochondria 6-Bactericidal action by lysosomes and peroxisomes 7-Transport

8. Endocytosis This is a process by which different substances are engulfed by the cell. It is the reverse of exocytosis. Types:- 1-Pinocytosis:- Pinocytosis is the ingestion of extremely small vesicles containing extracellular fluid.

11. It is involved in the formation of minute invaginations of the cell membrane.

14. The CM invaginates inwards and contractile proteins cause its border to close over the attached protein along with ECF, forming pinocytic vesicles.

16. It occurs in the same way as pinocytosis.

20. Phagocytosis occurs in following steps:- 1-The CM receptors attach to the surface of particle. 2-The edges of the membrane around the points of attachment evaginate outwards within a fraction of a second to surround the particle. After it more membrane receptors are attached to the particles.

21. Digestion by Lysosomes Cell can digest different substances with the help of enzymes. Lysosomes contain hydrolytic enzymes.

22. Exocytosis Removal of substances by the cells is called exocytosis. It is the reverse of endocytosis . This occurs when residual material in an endocytic vesicle is discharged from the cell. It is involved in cellular secretion of gland cells.

24. They are then extruded into secretary granules .

25. The granules move toward the CM, which fuses and leaves the contents of granules or vesicles outside the cell.

28. Lipid formation by SER:- SER mostly forms phospholipids and cholestrol.These go inside the membrane of ER, causing it to grow more extensive. Occurs mainly in SER.Also small ER vesicles or transport vesicles continuously breaks off from it and go to GA.

29. Other functions of ER Provides enzymes that control glycogen breakdown when glucose is used for energy. Provides vast number of enzymes which detoxify substances such as drugs It achieves detoxification by coagulation, oxidation, hydrolysis, conjugation with glycuronic acid etc

30. Specific functions of GA Processing of already formed substances. Capable of forming carbohydrates that cannot be formed by ER e.g Hyaluronic acid, chondroitin sulfate.

31. Functions of HA and CS 1-Major component of proteoglycans secreted in mucus and other glandular secretions. 2-Major portion of ground substance, outside cell in interstitial spaces, acting as filler b/w collagen fibers and cells 3-Principal component of organic matrix in cartilage and bone.

32. Processing by GA The transport vesicles fuse with GA and empty their secretions here. More carbohydrates are added to secretions. It compact the ER secretions into highly concentrated packets. Release in the cell in the form of lysosomes and secretary vesicles.

33. SV are abundant in secretary cells, which attaches to CM and release its secretions outside by exocytosis. This exocytosis is stimulated by Ca ions.

34. The membranous system of ER and GA represents a highly metabolic organ capable of forming new intracellular structures as well as secretory substances to be extruded from the cell.