1. Medical biology
Cytology/ lec3
01/03/1439
Farah E. Ismaeel

2. The Cytoplasm
The cytoplasm is the part of the cell located outside the nucleus full the space between nuclear envelop and plasma membrane consists of
cytosol is a larger fluid component.
Organelles (little organs) are bathing metabolically active structures. (living)
Cytoskeleton is protein components which determine the shape and motility of eukaryotic cells.
Inclusions are the minor cytoplasmic structures that are not usually surrounded by a plasma membrane. (non living)
01/03/1439
Farah E. Ismaeel

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Farah E. Ismaeel

4. Cytosol Cytosol is an aqueous gel called the cytoplasmic matrix.
The matrix consists of :
inorganic ions (Na, K, and Ca2)
organic molecules such as intermediate metabolites, carbohydrates, lipids, proteins, and RNAs.
contains hundreds of enzymes, such as those of the glycolytic pathway.
oxygen, CO2, electrolytic ions, low-molecular-weight substrates, metabolites, and waste products
01/03/1439
Farah E. Ismaeel

5. inclusions organelles
nonliving
living
temporary
permanent
Not essential
essential
inert
Active
Is only a result as fat
Have vital function
Some cells have it
All cells have it
01/03/1439
Farah E. Ismaeel

6. Inclusions
The cytoplasmic inclusions are temporary non-living structures that accumulate in the cytoplasm of certain cells not able to carry out any metabolic activity and are not bound by membranes.
Inclusions are stored nutrients, secretory products, and pigment granules.
01/03/1439
Farah E. Ismaeel

7. Example of inclusions
Glycogen: Glycogen granules is the most common form of glucose in animals and is especially abundant in cells of muscles, and liver 
Lipids: Lipids are triglycerides in storage form is the common form of inclusions, not only are stored in specialized cells (adipocytes) but also are located as individuals droplets in various cell type especially hepatocytes. These are fluid at body temperature and appear in living cells as refractile spherical droplets.
01/03/1439
Farah E. Ismaeel

8. Example of inclusions
Crystals: Crystalline inclusions have long been recognized as normal constituents of certain cell types such as Sertoli cells and Leydig cells of the human testis, and occasionally in macrophages
Pigments: The most common pigment in the body, besides hemoglobin of red blood cells is melanin, manufactured by melanocytes of the skin and hair, pigments cells of the retina and specialized nerve cells in the substantia nigra of the brain. These pigments have protective functions in skin and aid in the sense of sight in the retina but their functions in neurons is not understood completely. Furthermore, cardiac tissue and central nervous system neurons shows yellow to brown pigment called lipofuscin, some believed that they have lysosomal activity.
01/03/1439
Farah E. Ismaeel

9. Pigments Endogenous pigments they formed by the cells
Exogenous come from outside. like tattoo marks, carotene and dust the epithelial surface of lung alveoli where it ingests inhaled particulate matter known as dust cells.
01/03/1439
Farah E. Ismaeel

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Farah E. Ismaeel

11. Organelles
All cells have the same basic set of intracellular organelles, which can be classified into two groups:
(1) Membranous organelles with plasma membranes that separate the internal environment of the organelle from the cytoplasm.
(2) Non membranous organelles without plasma membranes.
01/03/1439
Farah E. Ismaeel

12. Vesicular as in smooth-surfaced endoplasmic reticulum
The membranes of membranous organelles have different form:
Vesicular as in smooth-surfaced endoplasmic reticulum
plicated as in the inner mitochondrial membrane.
01/03/1439
Farah E. Ismaeel

13. each type of organelle contains a set of unique proteins.
In membranous organelles, these proteins are either incorporated into their membranes or sequestered within their lumens. For example, the enzymes of lysosomes are separated by a specific enzyme resistant membrane from the cytoplasmic matrix because their hydrolytic activity would be detrimental to the cell.
In Non membranous organelles, the unique proteins usually self assemble into polymers that form the structural elements of the cytoskeleton.
01/03/1439
Farah E. Ismaeel

14. Membrane bounded organelles
Endoplasmic reticulum (ER)
The largest organelle of most eukaryotic cells is ER.
ER is a network of intercommunicating channels and sacs formed by a continuous membrane which encloses a space called cisternae this network (reticulum) extends from the surface of the nucleus to the cell membrane.
01/03/1439
Farah E. Ismaeel

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Farah E. Ismaeel

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Farah E. Ismaeel

17. Endoplasmic reticulum (ER)
The main function of ER is the transport of materials by forms transport vesicles in which large molecules are transported to other parts of the cell. Often, these vesicles are on their way to the plasma membrane or the Golgi apparatus.
There are two types of ER according to the present of ribosome, Rough ER and Smooth ER
01/03/1439
Farah E. Ismaeel

18. Rough ER (RER)
RER is studded with ribosomes on the side of the membrane that faces the cytoplasm.
Here, proteins are synthesized and enter the ER interior, where processing and modification begin. Some of these proteins are incorporated into membrane, and some are for export.
Is found in all cells except erythrocytes and is especially abundant in pancreas (pancreatic acinar cell that produce digestive enzymes), fibroblasts produce collagen and plasma cells that produce immunoglubins.
01/03/1439
Farah E. Ismaeel

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Farah E. Ismaeel

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Farah E. Ismaeel

21. Function of RER
Has role in the synthesis of protein to be exported outside the cell.
Modification of newly formed polypeptides.
Assembly of multichain protein.
Initial glycosylation of the glycoprotein which means addition of glucose to the protein.
01/03/1439
Farah E. Ismaeel

22. RER has a highly regulated system to prevent nonfunctional proteins being forwarded to the pathway for secretion or to other organelles.
New proteins that cannot be folded or assembled properly by chaperones undergo ER-associated degradation (ERAD), in which unsalvageable proteins are translocated back into the cytosol, conjugated to ubiquitin, and then degraded by proteasomes.
01/03/1439
Farah E. Ismaeel

23. Quality control during protein production in the RER and properly functioning ERAD to dispose of defective proteins are extremely important and several inherited diseases result from malfunctions in this system.
For example, in some forms of osteogenesis imperfect bone cells synthesize and secrete defective procollagen molecules which cannot assemble properly and produce very weak bone tissue.
01/03/1439
Farah E. Ismaeel

24. Thank you for listening
01/03/1439
Farah E. Ismaeel