3- Cell II (lysosomes, mitochondria, Nucleus).pptx

‫بسم الله الرحمن الرحيم‬ Organelles Lysosomes Mitochondria Nucleus Lysosomes The name lysosome derives from the Greek words lysis which means dissolution or destruction, and soma which means body  The hydrolytic enzymes digest most of the content of the lysosomes. Any indigestible subs...

‫بسم الله الرحمن الرحيم‬ Organelles Lysosomes Mitochondria Nucleus Lysosomes The name lysosome derives from the Greek words lysis which means dissolution or destruction, and soma which means body  The hydrolytic enzymes digest most of the content of the lysosomes. Any indigestible substances remain in lysosomes forming residual bodies. In long-lived cells, accumulated residual bodies indicate cellular aging and are called lipofuscin pigments. Structure: LM: Not seen but cause cytoplasmic eosinophilia - Where do we find lysosomes in large number? EM Products delivered to lysosomes for degradation arrive from several paths that include: 1- phagocytosis. 2- endocytosis. 3- autophagy: Intracellular particles such as worn-out or malfunctioning organelles are removed by a process called autophagy. The process begins with the enclosure of this organelle by membranes from sER, creating an autophagosome, which then fuses with a lysosome. Mitochondria  Mitochondria Mitos= thread chondros= granule - Rod shaped, filaments or granules - Energy factories (sites of ATP production). -Responsible for cell respiration  Structure of mitochondria LM: Not seen but cause cytoplasmic eosinophilia  EM of the Mitochondria Double membrane: -Outer smooth -Inner folded forming cristae Double spaces: - intermembranous space - matrix space intermembranous space Outer membrane: - smooth - permeable to small molecules due to transmembrane protein (porin) Inner membrane: folded (cristae). - impermeable due to specific phospholipid (cardiolipin) - protein enzymes for respiratory chain. - ATP synthesis by (ATP synthase): Lollipop-like protein complexes (ATP synthase) that form ATP. Intermembranous space: - substrates & ions similar to cytosol. :Matrix space 1. oxidative enzymes e.g. Citric acid cycle enzymes. 2. mitochondrial DNA: They can replicate themselves by division 3. few ribosomes 4. matrix granules that store calcium ions. Nucleus Largest organelle in the cell Membrane-limited compartment that stores the genetic information in cells. Location of assembly of ribosomal subunits Contains: Nearly all of the DNA in the cell The machinery to replicate DNA and to transcript f RNA Site It usually resides in the center of the cell It may be peripheral or basally situated  Shape Usually spherical but can be… The shape of nuclei present in a cell can assist in identifying the cell or tissue. Its shape often mimics the shape of the cell  Spindle-shaped Lobulated nuclei of fibroblast nuclei white blood cells (neutrophils)  Number Usually only one nucleus per cell but there are exceptions Osteoclasts (O) are multi- No nuclei are present nucleated in red blood cells Muscle fiber is Liver cell is multinucleated binucleated  Components of the Nucleus Nuclear envelope Nucleoplasm Chromatin Nucleolus  Components of the Nucleus 1- Nuclear Envelope – formed by two lipid membranes 2- Chromatin – both euchromatin and heterochromatin 3- Nucleolus – non-membranous, spherical structure  Components of the Nucleus 4- Nucleoplasm: semifluid colloidal protein solution. It is also known as the nuclear sap or matrix.  Nuclear Envelope It has a complex structure consisting of: 1. Two lipid bilayers (nuclear membranes) 2. An underlying nuclear lamina (Lamins) 3.Act as a barrier Nuclear pores. that separate the content of the nucleus from the cytoplasm : Nuclear Pores Nuclear pores are interruptions in the nuclear envelope where the outer and inner nuclear membranes fuse. Not uniformly distributed. There number varies from cell to other according of activity of the cell (3000-5000). Note nuclear pores (arrows) & bi-layered nuclear envelope Chromosomes and Chromatin Chromosomal DNA molecules of eukaryotes are thousands of times longer than the diameter of the nucleus and must therefore be highly compacted throughout the cell cycle. This folding is accomplished by combining the DNA with structural proteins to make chromatin.Chromatin= DNA+ histone Staining of the chromatin Basophili c Depending on structural and functional criteria, the DNA can be in the form of: 1. Heterochromatin  Inactive (low rate of transcription) 2. Euchromatin Active (high rate of transcription) Heterochroma tin Condensed. inactive type of chromatin. Light microscope: dense basophilic clumps. Electron microscope : condensed Distribution of heterochromatin 1-Peripheral heterochromatin 2- Heterochromatin islands 3-Nucleolar associated heterochromatin Heterochromatin acts as a reserve and is able to be transformed into euchromatin when needed. Euchroma tin Extended chromatin. Active chromatin: ready for transcription. Light microscope: light basophilic areas. Electron microscope: dispersed fine filaments.  The proportion between euchromatin and heterochromatin differs from one cell to another according to its functional activity  Heterochromatin Euchromatin (condensed chromatin) (extended chromatin) LM Dense basophilic clumps Lightly stained picture basophilic areas EM Electron- dense filaments Dispersed fine picture or filaments or granules; distributed in granules the following sites: 1. around the nucleolus (Nucleolar- associated heterochromatin) 2. associated with the inner nuclear membrane (Peripheral  Heterochromatin Euchromatin condensed( extended( chromatin )chromatin Functio The inactive part - The active part of ns of chromatin ,chromatin Acts as a reserve - i.e. chromatin that and is able can direct to be transformed DNA replication & into euchromatin RNAs transcription when needed Abund Inactive cells - Active cells e.g. - ant in dense nucleus dividing cells containing more cells with & heterochromatin synthetic activity and less i.e. pale nucleus euchromatin containing more euchromatin and less Nucleolus The nucleolus is the site of formation of rRNA as well as ribosomal subunit. Shape: spherical body within the nucleus with no surrounding membrane. Site: usually central in position. Size: large in active cells Number: active cells have multiple nucleoli. Nucleolus (Nu) Stains basophilic with H&E as it is the site of rRNA synthesis Thank you