Histological Structure and Function of Cell Organelles PDF

Mitochondria are membranous cell organelles....

Mitochondria are membranous cell organelles. Definition and Location Found in all cells except red blood corpuscles. Highly active cells (e.g., liver and cardiac The number of mitochondria depends on muscle cells) have numerous mitochondria. the cell's activity level. Inactive cells contain fewer mitochondria. Number and Activity Level Mitochondria can divide to increase their number. H&E staining shows acidophilia in cells with numerous mitochondria. Light Microscopy (LM) and Special Stains Special stains (e.g., Janus green, iron hematoxylin) reveal rounded or elongated structures. Two membranes (outer and inner). Mitochondria Structure Each mitochondrion consists of: Two spaces (intermembrane space and matrix). The outer membrane is smooth and contains porins for small molecule passage. The structure of the cell membrane that Electron Microscopy (EM) The inner membrane has folds called controls the movement of phospholipid cristae, increasing surface area for ATP molecules is cholesterol. Control of Phospholipid Movement production. Cell Membrane Structure and Function The organelle important for synthesizing The matrix contains enzymes, secretory proteins is the Rough mitochondrial DNA, ribosomes, and Endoplasmic Reticulum (RER). Organelle Functions electron-dense granules. Powerhouse of the cell, producing and storing energy as ATP. A network of anastomosing membranous channels called cisternae, found in two types: Rough Endoplasmic Reticulum Regulates intracellular calcium ion (RER) and Smooth Endoplasmic concentration. Reticulum (SER). Definition Functions Capable of self-replication due to its own By LM, RER gives basophilic areas. Histological DNA. Structure and Synthesizes proteins for its own use. By EM, it consists of parallel membrane- bounded channels (cisternae) with Structure Function of Cell ribosomes on the outer surface. Organelles Ribosomes are non-membranous cell Rough Endoplasmic Reticulum (RER) Synthesis of cell membrane proteins, organelles consisting of small and large lysosomal enzymes, and secretory proteins. Definition and Structure subunits made of proteins and rRNA. Prominent in protein-secreting cells (e.g., Function Endoplasmic Reticulum (ER) rRNA is synthesized in the nucleolus. fibroblasts, osteoblasts, plasma cells, pancreatic acinar cells). Ribosomal proteins are synthesized in the cytoplasm and imported to the nucleus to By LM, SER cannot be seen but may cause Synthesis of Ribosomes form subunits. cytoplasmic acidophilia when abundant. Structure Ribosomal subunits move from the By EM, it appears as anastomosing tubules nucleus to the cytoplasm. without ribosomes. Ribosomes cannot be seen by LM but Synthesis of membrane lipids Ribosomes cause cytoplasmic basophilia due to rRNA. (phospholipids and cholesterol). Smooth Endoplasmic Reticulum (SER) Light Microscopy (LM) and Electron By EM, they appear as electron-dense Synthesis of steroid hormones. Structure Microscopy (EM) granules. Synthesis of glycogen (in liver and muscle). Polyribosomes are clusters of ribosomes connected by mRNA. Drug detoxification (in liver cells). Functions Free ribosomes: not attached to membranes, synthesizing cytoplasmic Regulation of calcium ions during muscle proteins. contraction. Prominent in liver cells, muscle cells, and Types of Ribosomes Attached ribosomes: attached to RER steroid hormone-secreting cells. membranes, synthesizing membrane proteins, lysosomal enzymes, and secretory proteins.