Cilia and Flagella - Cell Biology PDF

Okay, here is the structured markdown format of the text in the images you sent. ### 9. Satellite Satellite is a rounded body separated from the rest of the chromosome by a secondary constriction. It is also known as trabant and the chromosome bearing satellite is called a SAT-chromosome (Sine Aci...

Okay, here is the structured markdown format of the text in the images you sent. ### 9. Satellite Satellite is a rounded body separated from the rest of the chromosome by a secondary constriction. It is also known as trabant and the chromosome bearing satellite is called a SAT-chromosome (Sine Acid Thymonucleriico-Chromosome). Morphology of chromosome is observed during metaphase but shape of chromosome is observed during anaphase. ### K. Cilia and Flagella Cilia (*L. cili-eye lash*) and flagella (*L. flagellum-whip*) are fine hair or filamentous appendage like movable structures present external to the cell but they are developed intracellularly from the basal body of cytoplasm. They help in locomotion or movement, feeding, circulation, etc. Cilia are smaller but numerous. Flagella are longer but fewer. Cilia are present in group ciliate of protozoan protista, external surface of many platyhelmenthes, larva of several annelids, mollusca and echinoderms, sperms of fern and cycad, etc. Flagella are present in group flagellate of protozoan protista, euglenoids, dinoflagellates, sperms of bryophytes and pteridophytes, zoospores and gametes of several algae and fungi. #### Structure Cilia and flagella have the same basis internal structure. They are surrounded by a thick unit membrane which is in continuation with the plasma membrane of the cell. The membrane encloses a matrix which has eleven fibrils or microtubules oriented along the long axis. Of these 11 fibres, nines are situated near the periphery in a cylinder and remaining two occur in the centre; thus showing 9+2 arrangements. Each peripheral fibril consists of two sub-fibrils. Hence, peripheral fibril is called a doublet. Out of the two sub-fibrils, one gives out two projections in clockwise direction. The two central fibrils are enclosed in a common sheath. Unlike the peripheral fibrils, each central fibril is made of a single tubule. In the distal end of the flagellum additional fibrils are present between peripheral and central fibrils. They are called secondary fibers much smaller in diameter than the peripheral and central fibrils. The image shows two diagrams. The first diagram is a cross-sectional ultrastructure of a flagellum. Key components labeled are: * Peripheral doublet fibril * Linker * Flagellar sheath * Outer and Inner side arms (provide energy) * Matrix * Plasma membrane * Subfibrils A, B, and C * Spokes * Central sheath * Central singlet * Transition junction The second diagram shows a longitudinal section (L.S.) of a flagellum, key parts labeled include: * Tip * Central singlet fibrils * Peripheral doublet fibril * Spoke * Knob * Transition junction * Central sheath * Flagellar sheath * Shaft * Basal plate * Basal granule * Hub * Rootlets In bacteria, flagellum consists of a single fibre of 9 + 0 arrangement. The bacterial flagellum is made of a fibrous protein called flagellin, while in other cases the peripheral fibrils contain a special type of protein called tubulin. #### Parts A cilium or flagellum consists of the following three parts: basal body, basal plate and shaft. 1. Basal body (blepheroplast, kinetosome or basal granule): It is embedded in the outer part of cytoplasm below the cell membrane. It is derived from a centriole. In the proximal half, the basal body has a cartwheel like structure consisting of nine peripheral triplet fibrils which is connected to a rod shaped central hub by means of radial spokes. The hub and radial spokes disappear in the distal end. Proximal end of basal body consists of rootlets. 2. Basal plate: It is a high-density plate like structure that lies between the basal body and shaft at the level of the cell membrane. 3. Shaft: It is a hair like exposed part of cilium or flagellum. It consists of sheath and axoneme. ##### Similarities between cilia and flagella Similarities between cilia and flagella are as follows: 1. Cilia and flagella develop from basal body 2. They have an internal supporting system in the form of rootlets. 3. Chemical compositions are similar. 4. Axoneme has similar fibrillar structure with nine peripheral duplet fibrils and two central singlet fibrils (9+2 arrangement). **Difference between cilia and flagella** | | Cilia | Flagella | | --- | --- | --- | | 1. | Each cell consists of hundreds or thousands of cilia (300-14000). | Each cell consists of one, two or rarely more flagella. | | 2. | They occur all over the cell surface. | They occur at one end of cell. | | 3. | They are shorter (2-10 $\mu$) in length. | They are longer (100- 150$\mu$) in length. | | 4. | They show pendular, sweeping, or rowing action. | They show undulatory action. | | 5. | Ciliary beating is asymmetrical. | Flagellar beating is symmetrical. | | 6. | They help in locomotion, circulation, aeration, protection, feeding, etc. | They help in locomotion only. | #### Functions of cilia and flagella Cilia and flagella show following important functions: 1. Cilia and flagella help in locomotion of cell or organism. 2. They create current for obtaining food from aquatic medium. 3. They help in removal of solid particles. 4. They show sensitivity in changing light, temperature and contact. 5. Tips of cilia and flagella secrete agglutinins to help in conjugation of gametes. 6. They create a current for movement of water for quick diffusion of $CO_2$ and refill of $O_2$. 7. The ovum released form ovary passes into infundibulum and fallopian tube due to ciliary action.