Biology Lecture 5 (2024-2025) PDF

Biology By: Dr. Shaimaa Zaher  Objectives Define cell inclusions Identify types of inclusions Recognize their structure by LM and EM.  Cytoplasmic inclusions Definition: structures formed from the metabolic products of cell. Unlike organelles, inclusio...

Biology By: Dr. Shaimaa Zaher  Objectives Define cell inclusions Identify types of inclusions Recognize their structure by LM and EM.  Cytoplasmic inclusions Definition: structures formed from the metabolic products of cell. Unlike organelles, inclusions are: ✓Non-living structures ✓Have little or no metabolic activity. ✓Transitory. ✓Not enclosed by membrane except melanin. ✓Not present in all cells. ✓Not essential to the vitality of the cell.  TYPES Stored food Pigments Glycogen Fat Exogenous Endogenous  A) Stored food 1) Carbohydrate: ✓Site: stored mainly in liver and muscle cells in the form of glycogen. ✓LM: ▪ H&E: glycogen appear vacuolated as it Glycogen stained with Best's dissolves during preparation. carmine in liver cells ▪ Special stains: PAS ✓Glycogen is stained by: ✓ Best's carmine Red ✓ Periodic Acid Schiff (PAS) magenta red  E.M: glycogen appears as electron dense granules. EM of Glycogen in liver cells 2) Fat: H&E ✓Site: stored mainly in fat cells in the form of lipid droplets. ✓LM: ▪ H&E: fat appears vacuolated as it dissolves during preparation. Sudan black Sudan III ▪ Special stains: fat is stained by: ✓ Sudan III → orange. ✓ Sudan black→ black. ✓ Osmic acid → black.  B) Pigments Are naturally colored materials. They are classified into two groups. 1) Endogenous pigments: Generated inside the body 2) Exogenous pigments: Introduced into the body form outside  Endogenous pigments They include: 1- Hemoglobin: is a red pigment in RBCs 2- Hemosiderin: ✓ It is an iron-containing dark brown pigment. ✓ It results from phagocytosis of RBCs. ✓Prominent in macrophages in the liver and spleen. 3- Melanin: ▪ Dark brown granules produced by melanocytes in skin. ▪ Melanin granules are surrounded by a membrane. ▪ It protects skin cells from ultraviolet radiation. 4- Lipofuscin: ▪ Golden brown pigment in cardiac muscle and Lipofuscin pigment nerve cells. ▪ Results from accumulation of residual bodies.  Exogenous pigments They include: Carotene: yellow pigment in carrots. Carbon and dust particles in dust cells (macrophages of the respiratory system). Tattoo marks. Which of the following statements best describes prokaryotic cells? A.Their nuclei are surrounded by nuclear envelope. B.They have membranous cell organelles. C.Their DNA is circular & not complexed with histones. D.Their sizes range from 10 to 100 microns. Answer: C Which of the following statements about eosin stain is true? A. It is a basic stain. B. Its color is blue. C. It stains basic structures in the cell. D. Nuclei have a high affinity to it. Answer: C Which of the following features best describes cytoplasmic organelles? A. They are metabolically inert. B. They are non-living structures. C. All of them are membranous. D. They are essential for cell life. Answer: D Which of the following best defines the term “exocytosis”? A. The uptake of material at one side of a cell and its discharge from the opposite side. B. The process by which proteins move from one cytoplasmic compartment to another. C. The discharge of materials in cytoplasmic vesicles from a cell following fusion of the vesicles with the plasmalemma. D. Diffusion of lipid-soluble molecules from a cell across the cell membrane. Answer: C Which of the following organelles can divide? A. Golgi apparatus B. RER C. Mitochondria D. SER Answer: C What is the organelle that regulates intracellular calcium for muscle contraction? A. RER B. SER C. Ribosomes D. Mitochondria Answer: B Enzymes of citric acid cycle are found in which of the following sites? A. Perinuclear space B. Mitochondrial intermembrane space C. Mitochondrial matrix D. Cisternae of endoplasmic reticulum Answer: C  Which of the following has folds to increase the surface area for more ATP production? A.Inner mitochondrial membrane B.Outer mitochondrial membrane C.Membranes of RER cisternae D.Saccules of Golgi apparatus Answer: A What is the organelle responsible for synthesis of cell membrane proteins? A. Free ribosomes B. RER C. Golgi apparatus D. Lysosomes Answer: B The cell membrane appears trilamellar when examined by EM ✓ at high magnification. Peripheral membrane proteins act as channels and carriers.  Cholesterols are loosely bound to the inner surface of the cell  membrane. Structures that accept the blue color of hematoxylin are called ✓ basophilic. Regarding affinity to water, heads of phospholipid molecules  are hydrophobic while tails are hydrophilic. Rough endoplasmic reticulum is responsible for cell  recognition and adhesion. Cells with high metabolic activity have few mitochondria.  Smooth endoplasmic reticulum is prominent in steroid ✓ hormone secreting cells. Rough endoplasmic reticulum causes cytoplasmic  acidophilia in protein secreting cells. Receptor mediated endocytosis depends on porin protein. 