CBSE Questions for Class 11 Medical Biology Cell The Unit Of Life Quiz 1 - MCQExams.com

• When ribosomes are present in the membrane of the endoplasmic reticulum it is called the rough endoplasmic reticulum. 
• RER is abundantly found in the cells that actively synthesize proteins. The synthesis of lipids takes place in the smooth endoplasmic reticulum.

Mycoplasma has plasma membrane as the outermost covering, it lacks a cell wall. So, the correct answer is 'Bacteria'.

$$\textbf{Correct option:D}$$ 

$$\textbf{Solution:}$$

$$\textbf{Option (A)}$$

$$\bullet$$ Nucleolus is absent, rather the DNA that forms the major nuclear material is not membrane bound(naked) and coiled in the cytoplasm ,it is also known as genophore/nucleoid/prochromosone (single naked chromosome).

$$\bullet$$ There is an additional circular DNA called plasmid which is a very important machinery for biotechnology , nitrogen fixation, resistance , fertility etc.

$$\textbf{Option (B)}$$

$$\bullet$$ Membrane bound organelles are absent in prokaryotic cells such as mitochondria,endoplasmic reticulum,lysosomes,golgi apparatus, microtubules,microfilaments and centrioles.

$$\textbf{Option (C)}$$

$$\bullet$$ Centrioles are minute microscopic microtubular cylindrical structures which can duplicate themselves ,producing astral poles and basal bodies without having DNA and a membranous converting . These structures are present in eukaryotic cells and plays a crucial role at the time of cell division.

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

$$\bullet$$ All the above option are correct.

$$\textbf{Hence, the correct option is (D)}$$

Correct option: C
Explanation:
Bacteria are prokaryotic, single-celled organisms, which, belong to the kingdom Monera. The bacterial cell has coiled DNA in a region called nucleoid and is devoid of membrane-bounded organelles. Bacteria do not have an organized cellular structure.
Amoeba is a unicellular eukaryote and belongs to the kingdom Protista.
Spirogyra and Chlamydomonas are green algae and belong to the kingdom Plantae. They have a complex cellular structure with membrane-bounded organelles.
So, the correct answer is option C.

• Lysosomes are called suicide bags because in the case of adversity they digest their own cell. They have hydrolytic enzymes that get activated at pH 4.8.

• The endoplasmic reticulum is a network of membranes found throughout the cell and connected to the nucleus. 
• It is of two types RER and SER. Rough ER (RER) is the endoplasmic reticulum attached to the ribosome and thus involves the formation and transportation of proteins. 
• Smooth ER (SER) is the endoplasmic reticulum devoid of the ribosome and involved in the production and transportation of lipids and steroids. 
• It is smooth because it is not studded with ribosomes and is associated with smooth slippery fats.

• Plastids are organelles found in plant cells. These are involved in the synthesis and storage of food. 
• Plastids are of different types- (1) chloroplasts, (2) chromoplasts, (3) leucoplasts. 
  
• Chromoplasts are plastids that are coloured due to the pigments that are produced and stored inside them that is not chlorophyll.
  
• They are found in fruits, flowers, roots, and senescent leaves and are responsible for their different colours.

• Lysosomes show polymorphisms because of their different shape and functions. 
• Primary lysosomes are newly formed lysosomes. 
• The fusion of a primary lysosome with a phagosome gives rise to secondary lysosomes.

• Form specialized compartments by selective permeability
  • Unique environment
  • Creation of concentration gradients
  • pH and charge (electrical, ionic) differences
• Asymmetric protein distribution
• Cell-Cell recognition
• Site for receptor molecule binding for cell signalling
  • Receptor binds ligand (such as a hormone)
  • Induces intracellular reactions
• Controls and regulates reaction sequences
  • Product of one enzyme is the substrate for the next enzyme
  • Can "line up" the enzymes in the proper sequence

• Lysosomes are membrane-bounded organelle which acts as waste disposal system of a cell. 
• They help to keep the cell clean by digesting the foreign material.
• Lysosomes contain digestive enzymes capable of breaking down all organic material. 
• When the cell membrane get ruptured and the cellular environment gets change, lysosomes may burst and the enzymes digest their own cell.
• Hence, they are known as suicide bags.
• So, the correct answer is 'Suicide bags'