Lecture 4: Subcellular Organelles and Cell Membranes PDF

‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ ‫كليه الطب‬ lecture 4 ‫قسم الكيمياء الحيوية والطبية‬ Subcellular Organelles and Cell Membranes Cells contain various organized structures, collectively called as cell organelles 1. Nucleus 2. Endoplasmic reticulum 3. Golgi apparatus 4. Lysosomes 5. Mitochondr...

‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ ‫كليه الطب‬ lecture 4 ‫قسم الكيمياء الحيوية والطبية‬ Subcellular Organelles and Cell Membranes Cells contain various organized structures, collectively called as cell organelles 1. Nucleus 2. Endoplasmic reticulum 3. Golgi apparatus 4. Lysosomes 5. Mitochondria 6. Plasma membrane 7. Transport mechanisms 1 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ ‫كليه الطب‬ lecture 4 ‫قسم الكيمياء الحيوية والطبية‬ 1- NUCLEUS It is the most prominent organelle of the cell. All cells in the body contain nucleus, except mature RBCs in circulation. Nucleus contains the DNA, the chemical basis of genes which governs all the functions of the cell . The very long DNA molecules are complexed with proteins to form chromatin and are further organized into chromosomes 2- ENDOPLASMIC RETICULUM (ER) It is a network of interconnecting membranes enclosing channels or cisternae, that are continuous from outer nuclear envelope to outer 2 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ ‫كليه الطب‬ lecture 4 ‫قسم الكيمياء الحيوية والطبية‬ plasma membrane. Under electron microscope, the reticular arrangements will have railway track appearance . 3- GOLGI APPARATUS 1. The Golgi organelle is a network of flattened smooth membranes and vesicles , Main function of Golgi apparatus is protein sorting, packaging and secretion 3 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ ‫كليه الطب‬ lecture 4 ‫قسم الكيمياء الحيوية والطبية‬ 4- MITOCHONDRIA 1. They are spherical, oval or rod-like bodies, about 0.5–1 μm in diameter and up to 7 μm in length, Erythrocytes do not contain mitochondria. 2. Mitochondria are the powerhouse of the cell, where energy released from oxidation of food stuffs is trapped as chemical energy in the form of ATP 3. Mitochondria have two membranes. The inner membrane convolutes into folds or cristae. The inner mitochondrial membrane contains the 4 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ ‫كليه الطب‬ lecture 4 ‫قسم الكيمياء الحيوية والطبية‬ enzymes of electron transport chain. The fluid matrix contains the enzymes of citric acid cycle, urea cycle and heme synthesis 5-LYSOSOMES 1. lysosomes are tiny organelles. Solid wastes of a wast are usually decomposed in incinerators. Inside a cell, such a process is taking place within the lysosomes. 5 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ ‫كليه الطب‬ lecture 4 ‫قسم الكيمياء الحيوية والطبية‬ Endocytic vesicles and phagosomes are fused with lysosome (primary) to form the secondary lysosome or digestive vacuole. Foreign particles are progressively digested inside these vacuoles. Completely hydrolysed products are utilized by the cell. As long as the lysosomal membrane is intact, the encapsulated enzymes can act only locally. But when the membrane is disrupted, the released enzymes can hydrolyse external substrates, leading to tissue damage. 6 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ ‫كليه الطب‬ lecture 4 ‫قسم الكيمياء الحيوية والطبية‬ 3. The lysosomal enzymes have an optimum pH around 5. These enzymes are a. Polysaccharide hydrolysing enzymes (alpha-glucosidase, alphafucosidase, beta galactosidase, alpha mannosidase, beta glucuronidase, aryl sulfatase) b Protein hydrolysing enzymes ( collagenase, elastase, peptidases) c. Nucleic acid hydrolysing enzymes (ribonuclease, deoxyribonuclease d. Lipid hydrolysing enzymes (fatty acyl esterase, phospholipases) 7 ) ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ ‫كليه الطب‬ lecture 4 ‫قسم الكيمياء الحيوية والطبية‬ 6 - PLASMA MEMBRANE 1. The plasma membrane separates the cell from the external environment. It has highly selective permeability properties so that the entry and exit of compounds are regulated. The cellular metabolism is in turn influenced and probably regulated by the membrane. The membrane is metabolically very active. 2. The enzyme, nucleotide phosphatase (5' nucleotidase) and alkaline phosphatase are seen on the outer part of cell membrane; they are therefore called ecto-enzymes. 3. Membranes are mainly made up of lipids, proteins and small amount of carbohydrates. The contents of these compounds vary according to the nature of the membrane. The carbohydrates are present as glycoproteins and glycolipids. Phospholipids are the most common lipids present and they are amphipathic in nature. Cell membranes also contain cholesterol. 8 ‫د رياض حنيوه‬ ‫جامعه وارث االنبياء‬ ‫كليه الطب‬ lecture 4 ‫قسم الكيمياء الحيوية والطبية‬ Reference TEXTBOOK OF BIOCHEMISTRY Sixth Edition For Medical Students DM VASUDEVAN MBBS MD FAMS FRCPath Distinguished Professor of Biochemistry College of Medicine, Amrita Institute of Medical Sciences, Cochin, Kerala (Formerly Principal, College of Medicine, Amrita, Kerala) (Formerly, Dean, Sikkim Manipal Institute of Medical Sciences, Gangtok, Sikkim) E-mail: [email protected] SREEKUMARI S MBBS MD Professor, Department of Biochemistry Sree Gokulam Medical College and Research Foundation Thiruvananthapuram, Kerala E-mail: [email protected] KANNAN VAIDYANATHAN MBBS MD Clinical Associate Professor, Department of Biochemistry and Head, Metabolic Disorders Laboratory Amrita Institute of Medical Sciences, Kochi, Kerala Email: [email protected] END OF THE LECTUER 9