Lysosomes and Vacuoles MCQ - Practice Questions with Answers

Lysosomes

• These are single membrane bound round or spherical organelles that function as digestive component and organelle-recycling facility of animal cells. 
• They are not found in the plant cells. 
• These were discovered by Christian de Duve in 1955. 
• They contain hydrolytic enzymes that function at the acidic pH. 
• Due to the presence of hydrolytic enzymes, they are also called suicidal bags. 

Formation of Lysosomes:

• The precursor molecules of the hydrolytic enzymes are synthesized in the RER. 
• They are then transported to the Golgi apparatus where these are changed to enzymes. 
• These enzymes are packed in large vesicles that pinch off from the Golgi apparatus to form the lysosomes. 

Types of Lysosomes:
Lysosomes can occur in different forms within the same cell. This phenomenon is called polymorphism. There are four types of lysosomes:

(1) Primary Lysosomes: They are newly formed vesicles that are smaller in size and contain granules of hydrolytic enzymes.
(2) Secondary Lysosomes: These are formed when the food vacuole (phagosome) fuses with lysosome. The digestion of food occurs in here and the undigested food remains in the secondary lysosome.
(3) Residual Bodies: These are the lysosomes with undigested food material. They fuse with the plasma membrane and remove the debris through exocytosis.
(4) Autophagic Vacuoles: When a number of primary lysosomes fuse to clear the worn-out organelle, autophagic vacuoles are formed. 

Functions of Lysosomes:

Lysosomes perform a number of functions such as intracellular digestion, extracellular digestion, autophagy, disposal of useless cells etc.

Vacuoles:

• Vacuoles are membrane bound,  enclosed compartments in the cells wherein water, nutrients and waste material are stored. 
• These are very prominent in the plant cells. 
• The fluid present in the vacuole of plant cells is called cell sap. 
• The membrane of the vacuole is called tonoplast. 

Formation of Vacuole:
These are formed through the pinching off from the ER. 

Functions of Vacuole:

• In plants, vacuoles play a direct role in seed germination, water storage and giving specific structure to foliage and blooms. 
• Some of the general vacuole functions include storage, maintenance of turgor pressure, regulation of internal pH and isolation of metabolic waste.