CBSE Questions for Class 11 Medical Biology Cell The Unit Of Life Quiz 16 - MCQExams.com

• Option A is incorrect as cell I lack nucleus which means that cell I is primitive type as compared to the cell II which has the nucleus. 
• Option B is correct as a lack of nucleus makes the cell I prokaryotic cell. 
• Option C is incorrect as earliest life forms were autotrophs while cell II lacks photosynthesizing ability which makes it heterotroph. 
• Option D is incorrect as both prokaryotic and eukaryotic cells have the cell membrane. 
• Option E is incorrect as cell II is heterotroph (lack photosynthesis) and hence is not from the plant while cell I show photosynthesis but is prokaryotic which rules out its possibility of being plant cell. 
  
  

• The cell membrane is composed of the lipid bilayer membrane. There are proteins embedded in the layer. 
• The structure of the cell membrane is known as a fluid mosaic model. There are phospholipids that can show some amount of flip flop movement. They can migrate from one layer to another layer. 
• This type of movement is shown by the lipid molecules. The proteins are fixed in the layer of the cell membrane. They do not show any type of movement.

• Plastids are a pigment containing double membrane-bound organelle which is the site of manufacture and storage of chemical compounds.
  
• Plastids are of three types on the basis of the pigments present within them:-
• 1. chloroplast (green plastid), 2. The chromoplast (coloured plastid) and 3. Leucoplast (colourless plastid).
• Leucoplasts can differentiate into specialized plastids and are of the following

1. Amyloplasts stores starch and helps to detect gravity,
2. Elaioplasts stores fat.
3. Proteinoplast stores and modifies proteins.

• So, the correct answer is 'Leucoplast'.

• Lysosomes are membrane-bound organelles which are capable of breaking down biomolecules such as proteins, nucleic acids, carbohydrates and lipids.
  
• They contain digestive enzymes that digest excess or worn out organelles, food particles, engulfed viruses or bacteria and macromolecules.
  
• It was discovered by Christian de Duve in the year 1955.
• So, the correct answer is 'de Duve'.

• The cellular organelle shown in the diagram is Rough endoplasmic reticulum.
  
• The endoplasmic reticulum (smooth and rough) is an interconnected network of flattened, membrane-enclosed sacs or tube-like structure which are evenly distributed throughout the cytoplasm.
  
• The RER is studded with ribosomes and thus, it is responsible for the synthesis of proteins.
• So, the correct answer is 'RER, protein synthesis'.

• Davson and Danielli in the year 1935 proposed that the cell membranes are made up of lipid bilayers which are coated with thin sheets of protein.
  
• This model of cell membranes has a lipid centre which is surrounded by single layers of lipid that are covered by single protein layers. 
• This theory is called pauci-molecular theory which illustrates that the cell membrane is a sandwich (protein-lipid-protein) which are applicable to all biological membranes.
• So, the correct answer is 'Danielli and Davson'.

• Plastid is an important site for the manufacture and storage of chemical compounds used by the cells of autotrophic organisms.
  
• Chromoplast is a plastid which consists of red, yellow and orange coloured pigments.
• They are usually found in fruits, flowers, roots and aged leaves which gives distinct colours to these plant parts.
• The chromoplasts contain a pigment called lycopene, which is present in the form of crystals within the lumina of membrane sacs.
  
• So, the correct answer is 'All of the above'.

Rough endoplasmic reticulum (RER) are responsible for the assembly of proteins. A signal peptide is a short peptide that is present at the N-terminus of the newly synthesized proteins. It is cleaved by signal peptidase in RER and then enters the lumen of rough endoplasmic reticulum. Protein folding takes place in the lumen of the endoplasmic reticulum. Smooth endoplasmic reticulum (SER) is involved in the synthesis of phospholipid and cholesterol. Protein glycosylation takes place in the  lumen of the RER. Thus, the correct answer is option C.

• Mitochondria is a double membrane bound structure involved in aerobic respiration and ATP production. 
• Lysosomes are the single membrane bound vesicular structure involved in digesting carbohydrates, proteins, lipids and nucleic acids.
• Ribosomes are the granular structure not bound by any membrane. 
• Nucleus is a double membrane structure . The outer membrane usually remains continuous with ER and the inner membrane called nuclear membrane.
• So, the correct option is 'Option C' .