Tag: single membrane bound organelles

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.