Flagella - class-XI

Basal bodies/ basal granules/ kinetosomes/ blepharoplasts are the micro-cylinders that lie below the plasmalemma at the base of flagella or cilia. Cilia and flagella are vibratile hair like narrow protoplasmic processes present on the free surface of the cell which are connected with motility. Each one is made up of four parts: basal body, rootlets, basal plate and shaft.

The shaft of cilia and flagella consists of an external sheath, semi fluid matrix and an axoneme. Axoneme has 9+2 fibrillar arrangement, comprising of nine peripheral doublet microtubule fibrils and two central singlet microtubule fibrils, central sheath, linkers and spokes. Certain flagella possess lateral hairs called flimmer filaments. Such flagella are called tinsel Flagella.

Prokaryotic and eukaryotic flagella are different in the structure but their function is similar as they are used for the locomotion in prokaryotes while in gametes of eukaryotes are also used for movement.

The cytoskeletal structures are of three types : microtubules (made of tubulin protein), microfilaments (made of actin protein) and intermediate fibres (made of keratin protein). 

Inside cilia and flagella is a microtubule-based cytoskeleton called the axoneme. The axoneme of primary cilia typically has a ring of nine outer microtubule doublets (called a 9+0 axoneme), and the axoneme of a motile cilium has two central microtubules in addition to the nine outer doublets (called a 9+2 axoneme). The axonemal cytoskeleton acts as a scaffolding for various protein complexes and provides binding sites for molecular motor proteins such as kinesin II, that help carry proteins up and down the microtubules.

Correct statements: (i) Cilia/flagella work like oars, (iv) they are covered by the plasma membrane, and (v) the axoneme structure (9+2 arrangement). (ii) is false because flagella are longer than cilia. (iii) is false because prokaryotic and eukaryotic flagella are structurally different.

The eukaryotic flagellum has an axoneme with a 9+2 arrangement, meaning 9 pairs (doublets) of microtubules arranged in a circle surrounding a central pair of microtubules.

A human body has a different type of cells which shows different types of movements at different places in the body.

While prokaryotic and eukaryotic flagella differ significantly in structure, protein composition, and mechanism of movement, both serve the common function of locomotion.

Movement of cilia and flagella in a eukaryotic cell is powered by ATP and these ATP molecules are hydrolysed into ADP+Pi in cilia and flagella by the activation of dynein protein
Nexin protein is found in cilia and flagella and it prevents microtubules from moving
Myosin of muscles- It is found in animals

The body of euglenoids are covered by a thin pellicle, that has oblique but parallelly arranged stripes. It provides it the flexibility to cause temporary changes in body shape. The pellicle strips slide over one another to help in metabolic. So, the correct option is 'Pellicle'.

• A cilium is an organelle found on eukaryotic cells and are slender, small protuberances that project from the much larger cell body.
• It works like oars, causing the movement of the surrounding fluid. They are primarily responsible for locomotion, either of the cell itself or of fluids on the cell surface.
• Hence Cilia are small structures which work like oars, causing the movement of the surrounding fluid is a True statement.
• So, the correct answer is 'True'.

Rhizoplast is a fibril which is a connecting link between blepharoplast, with the nucleus in flagellated cells or organisms. It is a striated contractile structure attached to the basal region of the cilium in a variety of ciliates and flagellates. Many regulate the flagellar beat pattern, and is sensitive to calcium concentration. They are composed of a 20 kD protein, rather similar to spasmin. The ciliary rootlet or rhizoplast, is a cytoskeleton-like structure that originates from the basal body at the proximal end of a cilium. It extends proximally toward the cell nucleus. Rootlets are typically 80-100 nm in diameter and contain cross stria distributed at regular intervals of approximately 55-70 nm. 

<br>So, the correct answer is option C.<br>

A basal body (synonymous with basal granule, kinetosome and in older cytological literature with blepharoplast) is an organelle formed from a centriole, and a short cylindrical array of microtubules. It is found at the base of a eukaryotic undulipodium (cilium or flagellum) and serves as a nucleation site for the growth of the axoneme microtubules. Centrioles, from which basal bodies are derived, act as anchoring sites for proteins that in turn anchor microtubules within centrosomes, and are known as the microtubule organizing center (MTOC).

Centrosome is composed of two centrioles lying at right angles to each other. Each centriole has a cartwheel constitution. There is a whorl of nine peripheral triplet fibres of tubulin tilted at an angle of 40 degrees. In cilia and flagella also the cartwheel structure is present but the fibrils have 9+2 arrangement- peripheral doublet fibrils are tilted at an angle of 10 degrees.

A cilium is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body. Inside cilia and flagella, is a microtubule-based cytoskeleton called the axoneme. The axoneme of primary cilia typically has a ring of nine outer microtubule doublets (called a 9+0 axoneme) and the axoneme of a motile cilium has two central microtubule singlets in addition to the nine outer doublets (called a 9+2 axoneme). A flagellum is a lash-like appendage that protrudes from the cell body of certain prokaryotic and eukaryotic cells. Flagella also has 9+2 arrangement of microtubules. They both contains inner growth along with outer growth of cytoplasm. They both are not the protective structures.

Vincristin and Vinblastin are important anti cancer drugs, isolated from Althea rosea. These drugs inhibit spindle formation and thus arrest uncontrolled division of cancer cells. Tubulin are important cytoskeletal elements. Actin, Myosin are important for cellular movements. Motor proteins utilizing the cytoskeleton for movement fall into two categories based on their substrates: Actin motors such as myosin move along microfilaments through interaction with actin. 

Cilium is an organelle found in eukaryotic cells and are hair-like appendages. Inside cilia, is a microtubule-based cytoskeleton called the axoneme. The axoneme of cilia has a ring of nine outer microtubule doublets and two central microtubule singlets in addition to the nine outer doublets, called 9+2 axoneme.
The organized beating of cilia, however, are produced by controlled sliding of outer doublet microtubules.

Dynein forms an integral part of cilia. It is a motor protein which converts the chemical energy contained in ATP into the mechanical energy of movement. Dynein transports various cellular cargo by "walking" along cytoskeletal microtubules towards the minus-end of the microtubule, which is usually oriented towards the cell center. 

• Centriole- The centrosome is made up of 2 centrioles which are right angled to each other and is composed of a protein known as tubulin.
• It produces spindle apparatus at the time of cell division.
• Each centriole has 9 peripheral groups of microtubules (triplet) with no central microtubules thus, this type of arrangement in centriole is called 9+0 pattern.
  
• So, the correct answer is 'Centriole'.

• Dynein arms refer to the structures that extend clockwise from one tubule of each microtubule (nine doublets) towards the adjacent doublet in the axoneme of cilia or flagella.
  
• Each axoneme contains eight or nine dynein heavy chains.
  
• The inner and outer dynein arms are two-headed structures which contain two heavy chains each.
  
• So, the correct answer is 'Two attached to sub fibre A'.

The autotrophic organisms are self feeders that can synthesize the organic compounds using the inorganic substances available in surroundings. Green plants synthesize organic compounds using carbon dioxide and water in presence of sunlight as captured by green pigment chlorophyll. Absence of chlorophyll indicates the heterotrophic mode of nutrition of the organisms wherein they depend on the organic compounds synthesized by other autotrophs. This makes option B incorrect and option D correct. Option A is incorrect as the question is about mode of nutrition; not mode of reproduction. Extracellular digestion refers to secretion of digesting enzymes onto the food present in surroundings followed by intake of digested food via phagocytosis or any other transport mechanism. Cilia are the hair like appandages that help organism to move food into the oral groove which in turn collect and move the food into the cell; the food vacuoles serve to store the food. This makes option C incorrect as presence of cilia, oral groove and food vacuole indicate intracellular digestion. Correct answer is D. 

The structural bilateral symmetry of cilia and flagella is attributed to the presence of the central sheath and the radial spokes/bridges connecting the doublets to the center.

In the axoneme of cilia and flagella, the peripheral microtubule doublets are typically tilted at an angle of approximately 10 degrees.

Flagella are found in both eukaryotic cells (like sperm cells or Chlamydomonas) and prokaryotic cells (like E. coli), although their structures are fundamentally different.

• Axoneme with 9+2 microtubular arrangement occurs in both cilia and flagella.
  
• Cilia and flagella are cellular projections which are covered by an extension of the plasma membrane. 
  
• They both have similar internal structures and are made up of microtubules.
• The microtubule arrangement within cilia and flagella is 9 + 2 arrangement of microtubules.
• It contains nine fused pairs of microtubules on the outer side of a cylinder and the two unfused microtubules at the centre.
• So, the correct answer is 'Both A and B'.

Tubulin belongs to the protein superfamily of globular proteins.Alpha and beta tubulins polymerize into microtubules. Microtubules function in many processes like structural support, intracellular transport, and DNA segregation. Microtubules emerge from microtubule organizing center in eukaryotic cells.

Calcium-dependent kinases (such as CDKs or CaMKs) play crucial roles in regulating various cellular processes, including the progression of the cell cycle.

Cilia are short, hair-like appendages found on the surface of many cells. They are typically numerous and move in a coordinated, sweeping, or pendular fashion to move fluid or particles across the cell surface.

Flagella are typically longer than cilia and move in a wave-like (undulatory) motion. This motion is generally independent of other flagella and symmetric in its wave propagation.

• Cilia can be defined as the tiny hair-like projections on the surface of the cell.
• These hair-like projections help in sweeping mucus, trapped dust and bacteria in the respiratory tracts.
  
• It beats asymmetrically by the sweeping action
• The asymmetrical beating pattern consists of two strokes- effective stroke and recovery stroke.
• In an effective stroke, the cilia are straight and generate flow in the same direction as its motion.
• Whereas, in recovery stroke, the cilia bend parallel to the surface and creates relatively weaker backward flow.
• So, the correct answer is 'Asymmetrically by sweeping action'.

Dynein is a family of cytoskeletal motor proteins that move along microtubules in cells. They convert the chemical energy stored in ATP to mechnical work, and hence are involved in movement of cilia and flagella.

Bacterial flagella are helically shaped structures containing the protein flagellin. The base of the flagellum (the hook) near the cell surface is attached to the basal body enclosed in the cell envelope. The flagellum rotates in a clockwise or counterclockwise direction, in a motion similar to that of a propeller. This movement is regultaed by plasma membrane.

Flagella are long, numerous hairlike projections from the plasma membrane. Flagella are longer and less in number than cilia. In multicellular organisms, cilia and flagella are the major means of locomotion in prokaryotic cells, both cilia and flagella are composed of microtubles.

Groups of dynein molecules responsible for movement in opposite directions are probably activated and inactivated in a coordinated fashion so that the cilia or flagella can move back and forth.

Pili, Fimbriae and flagella are structures that are found on the cell wall of the bacteria. These are structures that are made out of cellular components like proteins, for example, Pilli is made up of the protein pilin and flagella is made up of the protein flagellin.

• Cilia and flagella are small hair-like projections from the cell and are composed of microtubules which are arranged with their positive end at the outer tip of the axoneme.
  
• A microtubule is a tubular linear polymer of tubulin protein which is a part of the cytoskeleton that helps to provide structure and shape to the cytoplasm of a eukaryotic cell.
  
• So, the correct answer is 'Microtubules'.

The 9+2 arrangement of fibrils is characteristics of eukaryotes being comprised of 9 peripheral doublet and 2 central singlet fibrils. Although the 9 + 2 pattern is the fundamental pattern of virtually all cilia and flagella, the axonemes of certain sporozoan protozoans and some insect sperm show some interesting variations. The spermatozoids of flatworms are also atypical. The eel sperm shows 9+0 arrangement. These atypical cilia and flagella, which are all motile, show that the central pair of singlet microtubules is not necessary for axonemal beating and that fewer than nine outer doublets can sustain motility, but at a lower frequency.

Cilia are short, hair like appendages extending from the surface a living cell. Cilia are found exclusively in the prokaryotes.