CBSE Questions for Class 11 Medical Biology Cell The Unit Of Life Quiz 15 - MCQExams.com

Correct option : (C)

Explanation of the correct option :

• Lysozyme is an enzyme that is found mostly in tears & saliva. 
• They have antimicrobial nature by cleaving the peptidoglycan component of bacterial cell walls and causes the death of the bacteria.
  
• The fungal cell wall is made of chitin and not affected by lysozyme. 
• Viruses do not show the presence of cell walls. 

• Microsome fraction is obtained by ultracentrifugation of cell contents. 
• When post-mitochondrial supernatant is subjected to a centrifugal force of 50000 x g for two hours; the microsomal fraction settles down. 
• The fraction includes microsomes, endoplasmic reticulum, Golgi bodies etc. 
• Microsomes are broken pieces of ER often with attached ribosomes.

• The endoplasmic reticulum without attached ribosomes is called an agranular or smooth endoplasmic reticulum. 
• SER occurs in cells engaged in producing large quantities of lipids. SER has more tubules and vesicles. It gives rise to spherosomes. 
• Spherosomes are single half-unit membrane-covered small spherical organelles that synthesize and store fats. In some plants, spherosomes have lysosomal activity, e.g., maize root tip.
• So, the correct answer is option D.

Correct option: C
Explanation for correct option: 

• The smooth endoplasmic reticulum (SER) is a part of the endoplasmic reticulum which does not possess ribosomes studded on its membrane.
• It is involved in the detoxification of many poisons and drugs such as drugs, aspirin, insecticides (DDT), petroleum products and pollutants and converting them to safer water-soluble products. 
• Due to its function of detoxification, SER is abundant in the liver.  

• Plastids are cytoplasmic organelles found only in plant cells.
• Leucoplasts are colourless plastids and mainly help in the storage of food compounds like starch, proteins and oil drops. Such colourless plastids are present in underground roots, stems.

Flagella is the locomotory structure in bacteria. The number and location of flagella are distinctive for each genus. There are four types of flagellar arrangement.

1. Monotrichous: Single polar flagellum, e.g., Vibrio cholerae.  
   
2. Amphitrichous: Single flagellum at both ends, e.g., Alcaligenes faecalis. 
3. Lophotrichous: Tuft of flagella at one or both ends, e.g., Spirilla.
4. Peritrichous: Flagella surrounding the cell, e.g., Typhoid bacilli.

• The nucleoplasm is a viscous fluid enclosed in a double-walled membrane of the nucleus. 
• The mitochondrion is a membrane-bound organelle found in most eukaryotic cells. These structures are sometimes described as "the powerhouse of the cell" because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy.
• Chloroplasts are organelles, specialized subunits, in plant and algal cells. Their main role is to conduct photosynthesis, where the photosynthetic pigment chlorophyll captures the energy from sunlight, and stores it in the energy storage molecules ATP and NADPH while freeing oxygen from water.
• Ribosomes are the protein builders or the protein synthesizers of the cell. They are like construction guys who connect one amino acid at a time and build long chains. Ribosomes are special because they are found in both prokaryotes and eukaryotes. Thus, the correct answer is option C.

• The endoplasmic reticulum is the network of the membranous tube-like structure. It serves many functions, including the folding of protein molecules in sacs called cisternae and the transport of synthesized proteins in vesicles to the Golgi apparatus. 
• It provides strength to the cell cytoplasm. The ribosome is a large and complex molecular machine, found within all living cells, that serves as the site of biological protein synthesis (translation). 
• Ribosomes link amino acids together in the order specified by messenger RNA (mRNA) molecules. The endoplasmic reticulum is studded with ribosomes called rough endoplasmic reticulum involves the formation, modification, and transportation of protein. 
• Thus, the correct answer is option B.