CBSE Questions for Class 11 Medical Biology Cell The Unit Of Life Quiz 3 - MCQExams.com

$$\textbf{Correct option: }$$ D

$$\textbf{ Solution: }$$

$$\textbf{ Option (D): }$$

$$\bullet$$The Endoplasmic reticulum (ER) studded with ribosomes is known as the rough endoplasmic reticulum and are generally involved with protein synthesis. 

$$\bullet$$Generally, the ribosomes are the dense and spherical structures that occur freely in the cytosol and also remain attached to the rough endoplasmic reticulum (RER).

$$\bullet$$Smooth endoplasmic reticulum plays an important role in the biosynthesis of glycolipids, phospholipids and cholesterol. 

$$\bullet$$These lipids are used in the formation of plasma or cell membranes and various steroid hormones.

$$\bullet$$The enzymes present in the smooth ER synthesize fats (lipids), steroids and cholesterol.

$$\bullet$$The organelle plays a major role in synthesizing, processing, and transportation of protein and lipids. 

 $$\bullet$$The smooth endoplasmic reticulum (SER) showing the absence of ribosomes forms the lipid molecules of the plasma membrane. 

$$\bullet$$The rough endoplasmic reticulum shows the presence of ribosomes which are responsible for secreting proteins required for the formation of plasma membranes.

Hence, the correct answer is option (d).

• Lysosomes are single-unit membrane-enclosed microbodies that consist of a wide variety of hydrolytic enzymes. 
• Lysosomes show polymorphism and are of various types. 
• They are as follows-
  

$$\textbf{Correct answer: B}$$ 

$$\textbf{Option (A):}$$ 

$$\bullet$$ A centrosome is a semi-conservative organelle that is not bound by any membrane.

$$\bullet$$ It helps with the generation of spindle fibres during cell division. 

$$\textbf{Option (B):}$$ 

$$\bullet$$ Lysozyme is bound by a single-layered unit membrane.

$$\bullet$$ Lysozyme contains the hydrolytic enzyme which is responsible for digesting the cellular components. 

$$\textbf{Option (C):}$$ 

$$\bullet$$ Mesosome is a cell organelle which is bound by a double-layered membrane because it is produced due to infolding of the plasma membrane. 

$$\textbf{Option (D):}$$ 

$$\bullet$$ The nucleus contains a double-layered nuclear membrane which protects the internal genetic material inside the nucleus.

Hence, the correct answer is option (B).

• Ion channels are special proteins through which ions flow along the concentration gradient. These channels are important because the membrane is made up of a bilayer of lipids and will not allow the transport of water-soluble ions. 
• However, lipid-soluble components can dissolve in membrane lipids and can be transported across the membrane without special carrier or transport proteins.
• But all ions cannot pass through the same transport protein because the volume of each ion will be different. There are different transport proteins for the transport of different ions.

• The endoplasmic reticulum is of two types on the basis of the presence of ribosomes. If the endoplasmic reticulum ribosomes are attached to them then it is called a rough endoplasmic reticulum and if there are no ribosomes on the endoplasmic reticulum then it is called a smooth endoplasmic reticulum.
• The rough endoplasmic reticulum produces and transports protein and the smooth endoplasmic reticulum produces and transports lipid which provides a framework to the plasma membrane a known as membrane biogenesis.
• So, the correct answer is option A.

• The nucleus regulates all cellular activities by controlling the enzymes required for cellular processes. 
• Enzymes are proteins and protein synthesis is controlled by the nucleus.
• The mRNA required for protein synthesis is made from DNA, which is situated in the nucleus. 

• The nucleus contains a viscous liquid called nucleoplasm. It contains chromosomes and nuclei. It is surrounded by a nuclear membrane and it helps in the exchange of material between the nucleus and cytoplasm. 
• Protoplasm is the cytoplasm and nucleus of a cell.
  
• The cytosol is the part of the cytoplasm that is not held by any of the organelles in the cell.
  
• The cytoplasm is the part of the cell which is contained within the entire cell membrane. It is the total content within the cell membrane other than the contents of the nucleus of the cell.
  
• So, the correct answer is option B.

• RNA is found everywhere- nucleus, nucleolus, mitochondria, chloroplasts, ribosomes, cytoplasm, etc. RNAs are 3 different types- mRNA, tRNA and rRNA. mRNA and tRNA are found in the cytoplasm and rRNA in the nucleus.
• The ribosomes can be free within the cytoplasm of a cell or attached to the endoplasmic reticulum but do not present inside the nucleus. RNA and ribosomes act together resulting in the synthesis of proteins.

Lysosomes are the small membrane-bounded organelles that contain hydrolytic enzymes. Lysosomes digest the old or dead organelle and foreign particles and thus called as garbage disposal of the cell. Lysosomes are represented morphologically diverse organelle defined by the common function of degrading the intracellular material.

• Plastids are the organelles found only in plant cells. These are of three types, namely, chloroplast, i.e., green plastid, non-green chromoplast, and leucoplasts. Leucoplasts are non-pigmented or colorless plastids that are used for the storage of starch and oils.