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

• 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.
• The pH of the interior of lysosome ranges from 4.5 - 5 (acidic in nature).
• All the enzymes of the lysosome are acid hydrolases and are active at the acidic pH (pH= 5) which is maintained within lysosomes.
  
• So, the correct answer is '5'.

• Mitochondria have evolved from specialized bacteria therefore, they have a membrane similar to bacteria and possess their own DNA.
  
• In prokaryotes, the ribosome present is a 70S type.
• Ribosomes are known as protein factories because they are the main site of protein synthesis which is present in almost all the cells (attached to nucleic acids, mitochondria, chloroplast and are freely present in the cytoplasm). They are composed of ribonucleic acids and proteins.
• All living organisms possess ribosomes.
• So, the correct answer is '1, 2 correct'.
  

• The cell membrane is a phospholipid bilayer that are selectively permeable membranes which separate the interior of the cells (cell organelles and cytoplasm) from the outside environment or the extracellular space.
  
• These biological membranes or bilayers are made up of amphiphilic phospholipids which have both hydrophilic phosphate head and a hydrophobic tail that consists of two fatty acid chains.
  
• The term plasmalemma was coined by Nageli and Cramer in the year 1855.
• So, the correct answer is 'Nageli and Cramer'.

• Prokaryotic cells lack a well-developed or membrane-bound nucleus and cellular organelles.
• They also lack the cytoskeleton (microtubules, microfilaments) in the cytoplasm, therefore, they don't have centrioles.
• They also lack desmosomes (a cellular structure which is a modification of the cell membrane) for cell-to-cell adhesion.
• So, the correct answer is 'All of the above'.

• The cell membrane is a phospholipid bilayer that are selectively permeable membranes which separate the interior of the cells (cell organelles and cytoplasm) from the outside environment or the extracellular space.
  
• These biological membranes are composed of lipid bilayers that form a continuous layer and is made up of amphiphilic phospholipids which have both hydrophilic phosphate head and a hydrophobic tail that consists of two fatty acid chains.
• The protein molecules are embedded in the lipid bilayer and some amount of carbohydrates are also present in the cell membrane.
• So, the correct answer is 'Proteins embedded in a phospholipid bilayer'.

• 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.
  
• A smooth endoplasmic reticulum lacks ribosomes.
• It helps in the production and metabolism of lipid, it also produces steroid hormones and helps in detoxification.
• So, the correct answer is 'Steroid synthesis'.

• Enzymes facilitating transport across the cell membrane is permease.
• Permeases are the transport proteins present in the cell membrane or a class of transmembrane proteins.
• Its main function is to allow the diffusion of a specific molecule or ions into or out of the cell in the direction of a concentration gradient (facilitated diffusion).
• So, the correct answer is 'Permease'.

• Leucoplasts is a colourless plastid that synthesis monoterpene an also get differentiated into more specialized plastids such as amyloplasts, elaioplasts and proteinoplasts etc.
  
• Elaioplast is a plastid which stores oils.
• So, the correct answer is 'Elaioplasts'.

• Ergastoplasm is the alternate name of the endoplasmic reticulum.
  
• The granular endoplasmic reticulum is also known as ergatoplasm.
• The ER in which ribosomes are found on the cisternae which are involved in the synthesis of proteins and are transported by the membrane-bound vesicles to the extracellular space.
• So, the correct answer is '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 interconnected flattened sacs of the endoplasmic reticulum are called cisternae.
  
• So, the correct answer is 'Cisternae'.

• Protein storing plastids are called Aleuroplast.
  
• The colourless plastid or leucoplast gets differentiated to form alueroplast or proteinoplast.
• Its main function is to store proteins in plant cells.
• So the correct answer is 'Aleuroplasts'.

• The mitochondria is a double-membraned cell organelle, known as the powerhouse of the cell which is present in all eukaryotic cells.
  
• The nucleus is enclosed by the nuclear envelope which is a double-layered membrane that consists of nuclear pores to regulate the transportation of substances such as RNA into and out of the nucleus. 
• The chloroplast is also covered by a double membrane which is known as the chloroplast envelope.
• So, the correct answer is 'Mitochondria, nucleus and chloroplast'.

Correct Option: B

Explanation: 

• Porins are channels present on the outer membrane of mitochondria and some bacteria.

• It is made of a trimer of the beta-barrel transmembrane protein.

• It acts as a specific pore or channel that is large enough to allow the passive diffusion of substance.

• These are found in mitochondria, chloroplast, and external membranes of gram-negative bacteria.

• These are useful in the regulation of diffusion of small molecules like sugars, amino acids, and ions also.

hence, porins are proteins.

• Most unicellular organisms are of microscopic size and are thus classified as microorganisms, for example, Phytoplankton and protozoa range from about 0.001 mm to about 0.25 mm.
• Most of the multicellular organisms and vertebrates are visible to the naked eye, which means that it is possible to view them without using the microscope.
  So, option A is the correct answer.
  

• The Endoplasmic reticulum (ER) is a eukaryotic organelle that forms an interconnected network of tubules, vesicles, and cisternae within cells. Rough endoplasmic reticulum synthesizes proteins, 
• while smooth endoplasmic reticulum synthesizes lipids and steroids, metabolizes carbohydrates and steroids and regulates calcium concentration, drug detoxification and attachment of receptors on cell membrane proteins. Sarcoplasmic reticulum solely regulate calcium levels.

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

$$\textbf{ Solution: }$$

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

$$\bullet$$Lysozyme is a naturally occurring enzyme. 

$$\bullet$$This enzyme is generally present in the bodily secretions such as tears, saliva, and milk.

$$\bullet$$ It functions as antibacterial agent by cleaving the peptidoglycan component of bacterial cell walls 

$$\bullet$$This can result in the death of the bacterial cell 

Hence, the correct answer is option (b).