Tag: membrane bound organelles

A chromosome with the median centromere and two equal arms are called as metacentric chromosomes. The presence of centromere at the terminal end makes telocentric chromosome. Acentric chromosomes lack centromere and therefore have a single arm. The presence of centromere in diffused state makes the polycentric chromosomes as if they have multiple centromeres Thus, the correct answer is option A.

In a plant cell, the vacuoles are large and centrally placed organelle. Vacuoles typically contain salts, sugars and sometimes proteins and have a variety of secretory, excretory and storage functions. The vacuole may also be involved in the breakdown of old organelles or macromolecules and then recycling the products back to the rest of the cell. Thus, they are in large number in a cell adapted for waste storage and disposal.
So, the correct answer is option A.

• The cell sap is a non-living content of the vacuole. Cell sap is the fluid manufactured by the cytoplasm of the living plant cell.
•  Cell sap consists of water and various substances that are often in the form of a colloidal suspension. 
• On average, cell sap has twice the viscosity of water. 
• The cell sap contributes to the osmotic properties and turgor of the cell, and consequently, to the elasticity of plant tissues and organs. 

The vacuole is a membrane-enclosed fluid-filled sac found in plant cells that occupies a major part of the cell volume. It gives rigidity to the cell and hence to the plant by using water to develop a pressure called hydrostatic pressure. It stores nutrient and non-nutrients such as pigments and mineral ions. It also stores the cellular metabolic waste. Thus the correct answer is option C.

The kinetochore is a protein complex assembled at each centromere. It acts as an attachment site for spindle microtubules for chromosomal movement to the opposite poles. Thus the correct answer is option B.

Vacuole is the characteristic feature of plant cell while absent in animal cell. The liquid substance present in the vacuole is called cell sap. The cell sap is mainly composed of water, sugar, salt, pigment- anthocyanin. Vacuole functions as store house for secretory and excretory substances. Thus option B is the correct answer.

• The function and significance of vacuoles vary greatly according to the type of cell in which they are present.
• In general, the functions of the vacuole include- Isolating materials that might be harmful or a threat to the cell. Containing waste products. 
• Containing water in plant cells. Maintaining internal hydrostatic pressure or turgor within the cell. Maintaining an acidic internal pH. 
• Allows plants to support structures such as leaves and flowers due to the pressure of the central vacuole etc.
  
  Therefore, the correct answer is option D.

The contractile vacuoles are the structures which are present in the cells of the lower organisms. The vacuole plays an important role in excretion and osmoregulation. The wastes like the ammonia can be excreted through the vacuoles. The water and the other salts are also removed through this vacuoles in order to maintain the osmotic balance.