CBSE Questions for Class 11 Medical Biology Cell The Unit Of Life Quiz 2 - MCQExams.com

Protists, fungi, plants and animals belong to domain eukarya and are eukaryotic organisms. Bacteria are unicellular prokaryotic organisms that lack a well-defined nucleus and other membrane-bound organelles. Thus, the correct answer is E.

The organelles present in the cytoplasm of the eukaryotic cells are essentially surrounded by their own unit membrane.

I. Ribosomes do not have any membrane. These are made up of ribonucleoproteins.

II. Plasma membrane that surrounds the whole cytoplasm itself is a membrane.

III. The endoplasmic reticulum is surrounded by a membrane.

IV. Golgi bodies are surrounded by a membrane.

Hence, the correct answer is 'II, III and IV'.

• The nucleus is the centrally located small spherical structure in an animal cell. It regulates and coordinates various activities of the cell. 
• The cytoplasm is the semi-liquid, colorless, and translucent part of the cell. It is found between the cell membrane and nucleus.
  
• A vacuole is found in the cytoplasm and helps to transport a number of ions against the concentration gradient, excretion, etc. It may or may not be present in an animal cell, if present is very small.
• Plastid is the largest cell organelle. Animal cell lacks plastids. They bear some specific pigments and imparting specific colours to the plant.

• Water transport is a physical process and not a physiological process. It does not require living cells and protoplasm. 
• The driving force is the transpiration pull generated by the loss of water through leaves. This is the reason why xylem tracheids and vessels are dead on maturity. 
• Food transport is a physiological process and requires living cells similarly stomatal movement also is a physiological process and requires living cells.

• Lipid molecules in the plasma membrane form a bilayer with hydrophobic tails buried inside the central region and hydrophilic heads towards the two surfaces. 
• According to the fluid mosaic model of Singer and Nicolson, cell membranes are quasi-fluid in nature with a viscous lipid bilayer having proteins at places (mosaic) both on the surface and inside. 
• The arrangement of lipids in the bilayer is also called head parallel arrangement because the polar heads of both the lipid layers are oriented on the surface and hydrophilic tails are embedded towards the inside of the membrane.

• Desmosomes are a modification of plasma membrane. These are just like welded areas between adjacent cells having intercellular thickening materials. 
• They are transmembrane linkers made up of disc-shaped intracellular thickening adjacent to each membrane.

• Prokaryotic cells are devoid of membrane-bound organelles like the nucleus, mitochondria, ER, etc.
• Mesosomes or chondroid are formed due to invaginations of the plasma membrane of bacteria and serve as the respiratory center.
• These are of two types - septal mesosomes and lateral mesosomes. 
• Mesosomes are more prevalent in Gram +ve bacteria and they are rich in respiratory enzymes.
• The ribosome is the nonmembrane-bound organelle hence is present in a prokaryotic cell but it is not formed due to the extension of the plasma membrane.