LECTURE----3 DR ZAHOOR ALI SHAIKH. CELL PHYSIOLOGY-----2. CYTOPLASM CYTOSOL AND CYTOSKELETON. What is Cytosol ? Cytosol is semi liquid portion of the cytoplasm that surrounds the organelles. It occupies 55% of cell volume. It is like a gelatinous mass. FUNCTIONS OF CYTOSOL.
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1- Ribosomal protein synthesis
Free ribosome's are present in cytosol , which synthesize protein.
2- Intermediary Metabolism
It involves degradation, synthesis. Thousands of Enzymes involved in Glycolysis are found in cytosol.
3- Storage of Fat, carbohydrate (Glycogen), and secretary vesicles
3- Intermediate Filaments
movement of cilia and flagella.
a) Contractile systems E.g. Actin and Myosin are (protein molecule) present in muscle for muscle contraction
(Non-motile ,hair like projection from the surface of epithelial cells of small intestine)
1. Cilia, Flagella by Microtubules.
2. Actin and myosin (muscle contractile units) and microvilli by Microfilaments.
3). Intermediate Filament
1. Phospholipids forms basic structure of membrane.
2. It is Hydrophilic (water liking) outside and Hydrophobic (water fearing) inside.
3. It is responsible for fluid nature of cell membrane.
i. Protein form channels– Ions pass through these channels, e.g. Na+, K+, Ca++.
ii. Channel allow up to the size of 0.8nm (Nanometer).
iii. Other protein serve as carrier molecule.
Each carrier can carry only particular molecule e.g. Thyroid gland cells can carry Iodine from blood to Thyroid gland (other body cells can not).
iv. Protein on cell membrane (outer surface) serve as receptor sites e.g. Hormones can act on different receptors.
v. Some protein on the interior of the cell combine with secretary vesicles and empty its content outside by EXOCYTOSIS.
vi. Other protein function as enzymes on both sides of membrane (they are embedded in the plasma membrane).
vii. Protein on plasma membrane serve as CELL ADHESION MOLECULES (CAMs).
viii. 0ther protein with carbohydrate are important to recognize “SELF”.
i. Work as self identity marker.
ii.Carbohydrate surface marker are involved in Tissue growth within physiological limits.
1. Cell Adhesions Molecules (CAM) —proteinin plasma membrane
2. Extracellular Matrix
3. Specialized Cell Junctions
1. Cell Adhesions Molecules (CAMs) already mentioned (made by proteins).
2. Extra cellular Matrix (ECM)
- It works as biological “Glue”
- It is mesh work of fibrous protein embedded in watery gel substance of complex carbohydrate.
Present in this gel (carbohydrate) are THREE types of protein fibers:
i. Collagen e.g. skin , gums
ii. Elastin- rubber like protein, present in LUNGS –stretch and recoil during breathing
iii. Fibronectin- increases cell adhesion , it is decreased in cancer cells , therefore cancer cell break and metastasize (spread in body).
2) Tight junctions
3) Gap junctions
[Microtubules – cilia, flagella
Microfilament – Actin, Myosin and Microvilli
Intermediate filament-Neurofilaments in nerve cell]
E.g.: Protein Channels, Receptors, Enzymes, Carrier Mediated Transport, Cell Adhesion Molecules