بعض الصور عن الخلية

Dr.Ahmad

Figure 2–3. A: The fluid mosaic model of membrane structure. The membrane consists of a phospholipid double layer with proteins inserted in it (integral proteins) or bound to the cytoplasmic surface (peripheral proteins). Integral membrane proteins are firmly embedded in the lipid layers. Some of these proteins completely span the bilayer and are called transmembrane proteins, whereas others are embedded in either the outer or inner leaflet of the lipid bilayer. The dotted line in the integral membrane protein is the region where hydrophobic amino acids interact with the hydrophobic portions of the membrane. Many of the proteins and lipids have externally exposed oligosaccharide chains. B: Membrane cleavage occurs when a cell is frozen and fractured (cryofracture). Most of the membrane particles (1) are proteins or aggregates of proteins that remain attached to the half of the membrane adjacent to the cytoplasm (P, or protoplasmic, face of the membrane). Fewer particles are found attached to the outer half of the membrane (E, or extracellular, face). For every protein particle that bulges on one surface, a corresponding depression (2) appears in the opposite surface. Membrane splitting occurs along the line of weakness formed by the fatty acid tails of membrane phospholipids, since only weak hydrophobic interactions bind the halves of the membrane along this line. (Modified and reproduced, with permission, from Krstíc RV: Ultrastructure of the Mammalian Cell. Springer-Verlag, 1979.)

Figure 2–12. Three-dimensional representation of a mitochondrion with its cristae penetrating the matrix space. Note that 2 membranes delimiting an intermembrane space form the wall of the mitochondrion. The cristae are covered with globular units that participate in the formation of ATP.

Figure 2–27. Current concepts of the functions of lysosomes. Synthesis occurs in the rough endoplasmic reticulum (RER), and the enzymes are packaged in the Golgi complex. Note the heterophagosomes, in which bacteria are being destroyed, and the autophagosomes, with RER and mitochondria in the process of digestion. Heterophagosomes and autophagosomes are secondary lysosomes. The result of their digestion can be excreted, but sometimes the secondary lysosome creates a residual body, containing remnants of undigested molecules. In some cells, such as osteoclasts, the lysosomal enzymes are secreted to the extracellular environment. Nu, nucleolus.

Figure 2–34. Schematic representation of microtubules, cilia, and centrioles. A: Microtubules as seen in the electron microscope after fixation with tannic acid in glutaraldehyde. The unstained tubulin subunits are delineated by the dense tannic acid. Cross sections of tubules reveal a ring of 13 subunits of dimers arranged in a spiral. Changes in microtubule length are due to the addition or loss of individual tubulin subunits. B: A cross section through a cilium reveals a core of microtubules called an axoneme. The axoneme consists of 2 central microtubules surrounded by 9 microtubule doublets. In the doublets, microtubule A is complete and consists of 13 subunits, whereas microtubule B shares 2 or 3 heterodimers with A. When activated by ATP, the dynein arms link adjacent tubules and provide for the sliding of doublets against each other. C: Centrioles consist of 9 microtubule triplets linked together in a pinwheel-like arrangement. In the triplets, microtubule A is complete and consists of 13 subunits, whereas tubules B and C share tubulin subunits. Under normal circumstances, these organelles are found in pairs with the centrioles disposed at right angles to one another.

Figure 2–35. Drawing of a centrosome with its granular protein material surrounding a pair of centrioles, one shown at a right angle to the other. Each centriole is made of 9 bundles of microtubles, with 3 microtubules per bundle.



from Basic Histology Atlas

مجهول

بسم الله الرحمن الرحيم شـكــ وبارك الله فيك ـــرا لك ... لك مني أجمل تحية . موفق بإذن الله ... لك مني أجمل تحية .

مجهول

شـكــ وبارك الله فيك ـــرا لك ... لك مني أجمل تحية .

الفتاة الحالمة

مشكور حكيم ع إضافاتك الرائعة ولك مني تحية غالية

مجهول

[read] شكرا لك وبارك الله فيك[/read]

مجهول

thanksssssssssssssssssssss