Cell Structure MCQ Quiz - Objective Question with Answer for Cell Structure - Download Free PDF

The correct answer is Protein synthesis.

Explanation

Ribosomes are small and complex structures within cells that are involved in one of the most vital processes needed for life i.e. protein synthesis. They link amino acids together in the order determined by messenger RNA (mRNA) molecules.

Here's some detailed information on Ribosomes:

Structure: Ribosomes are made up of two subunits: a larger one and a smaller one. Both of these subunits are composed of a special class of RNA known as ribosomal RNA rRNA and proteins.

• In eukaryotes, the larger subunit is known as the 60S subunit and the smaller one is the 40S subunit, together forming the complete 80S ribosome
• In prokaryotes, the smaller subunit is the 30S subunit, and the larger one is the 50S subunit, making an overall smaller 70S ribosome.

Function: The main function of ribosomes is to carry out protein synthesis. This process is also known as translation and involves decoding mRNA which was previously transcribed from the cell's DNA to build a chain of amino acids, which will become a protein. This means ribosomes are the site where the cell's genetic information is used to create proteins.

Location: Ribosomes are found both in the cytoplasm free ribosomes and attached to the endoplasmic reticulum ER, creating what is known as the rough ER. Free ribosomes typically synthesize proteins that function within the cytoplasm, while those associated with the ER synthesize proteins that are either exported from the cell, incorporated into the cell's membranes, or sent to lysosomes.

Conclusion Ribosomes are sites for protein synthesis.

The correct answer is cytologyKey Points

• Cytology is the study of individual cells of the body, in contrast to histology which is the study of whole human tissue.
  • The human body is made up of millions of cells and these can be sampled and viewed under a microscope after appropriate preparation to help diagnose medical conditions.
  • This involves looking at individual cells for abnormal changes in both the nucleus and the cytoplasm (body) of the cell.
  • The nucleus contains the genetic material that controls the cell and determines what type of cell it will become, but also controls its behavior.
  • Cytology is widely used in medicine for the prevention and diagnosis of disease.

Additional Information

• Robert Hooke was the first scientist to use the word 'cell' in 1665 when he looked at slices of cork through a lit compound microscope and observed very small, irregular boxes that reminded him of tiny rooms, or cells.
  • Hooke wrote about his findings and drew the structures he saw in his book Micrographia, which was published in 1665.
• The earliest cell theory was developed in 1838 by plant scientist Matthias Schleiden and animal scientist Theodor Schwann.
• They each came to the same conclusion that the living things they studied were composed of cells. 

The correct answer is Glicial cells

Key Points

• The cells of the nervous system that are supported, protected, and nurtured are called glial cells.
• Glial cells, also known as glia, surround neurons and provide support for and insulation between them.
• Glial cells are essential for the overall health of the nervous system, playing crucial roles in nutrient supply to nerve cells and maintenance of homeostasis.
• Unlike neurons, glial cells do not conduct electrical impulses. Their primary role is to support neurons.

Additional Information

The correct answer is : Cell Wall Key Points

• Cell Wall: The cell wall is a rigid layer present outside the plasma membrane in plant cells. It provides structural support, protection, and helps in maintaining the cell's shape. The primary component of most plant cell walls is cellulose, a complex carbohydrate. In contrast, animal cells lack a cell wall; they only have a plasma membrane, which is flexible. 
• Plastids: Plastids are organelles present only in plant cells. An example of a plastid is the chloroplast, which contains the pigment chlorophyll used in photosynthesis to convert light energy into chemical energy. Chloroplasts are a vital part of plant cells, enabling them to produce food. Plastids can also store food in the form of starch and can contain pigments that give flowers and fruits their colors. However, animal cells do not have plastids because they do not carry out photosynthesis.
• Mitochondria: Mitochondria are organelles that produce ATP (adenosine triphosphate), the energy currency of cells through a process called cellular respiration. These organelles are present in both plant and animal cells, so this option cannot be unique to plant cells.
• Lysosomes: Lysosomes are present in both plant and animal cells, even though their abundance in differing types of cells can vary. They are involved in intracellular digestion, breaking down waste materials, and cellular signaling. However, while they are widely recognized as a feature of animal cells, the presence, and role of lysosomes in plant cells have long been a subject of debate, with some evidence suggesting the existence of “lysosome-like” vacuoles.

The correct answer is Nucleoid.

Key Points

• In prokaryotic organisms, the nuclear region is not surrounded by any membrane.
  • The undefined nuclear region lacking a nuclear membrane and containing only DNA without proteins in bacteria is called the nucleoid.
• Prokaryotic cells are primitive organisms.
  • In prokaryotes, the nucleoid contains all or most of the genetic material.
  • In prokaryotic cells, the nucleus is not well-defined because it is not surrounded by the nuclear membrane.

Additional Information

• A nucleosome is a section of DNA wrapped around a core of protein.
  • Inside the nucleus, DNA forms a complex with a protein called chromatin, which allows the DNA to condense into small amounts.
• A nucleus, as it relates to genomics, is a membrane-bound organelle within a cell that contains chromosomes.
  • A series of pores, or pores, in the nuclear membrane allow selective passage of certain molecules (such as proteins and nucleic acids) in and out of the nucleus.
• Nucleoproteins are a type of proteins that are associated with nucleic acids and ribosomes and lipoproteins, they often serve as lipid transport and storage proteins such as vitelline.
  • A nucleoprotein is a conjugated protein structure consisting of a protein linked to a nucleic acid, either DNA abbreviated as deoxyribonucleic acid or RNA abbreviated as ribonucleic acid.

The correct answer is Option 4. 

Key Points

• Amoeba is a type of cell or unicellular organism which has the ability to alter its shape, primarily by extending and retracting pseudopods.
• The best known amoeboid protists are Chaos carolinense and Amoeba proteus, both of which have been widely cultivated and studied in laboratories.
• Amoeba does not have cell walls, which allows for free movement.
• Amoeba ingests food through a process known as phagocytosis. During this process, the pseudopodia formed by the amoeba surrounds and engulfs any food particle.

Additional Information

The correct answer is Endoplasmic Reticulum

Key Points

• Endoplasmic Reticulum (ER) is a large structure that helps in protein synthesis, calcium storage and lipid metabolism in the cell.
• It is a complex network of enclosed tubules that extends from the nuclear membrane and is located in the cytoplasm of the Eukaryotic cell.
• Endoplasmic Reticulum acts as a channel or a passage and lets proteins and lipids pass through it. Hence option 4 is correct.
• It is of two types: Smooth ER and Rough ER.
• The Rough ER is covered by ribosomes and functions in protein processing.
• The smooth ER is involved in lipids, instead of protein and metabolism.

Additional Information

• The Golgi Apparatus is a cell organelle that processes the proteins and lipid molecules and proteins that are destined to be exported from the cell.
  •  It is a part of the cell that is made up of membranes and some of them are tubules and nuclei.
• Lysosomes are membrane surrounded by cell organelle that contains digestive enzymes and helps break down excess or cell parts.
  • ​Apoptosis is the process in which if the cell is destroyed beyond repair, then the lysosomes help it to self-destruct.
• Mitochondria or called the powerhouse of the cell is a membrane-bound cell organelle which generates most of the chemical energy required for the cell.

Concept:

• The cell is the basic structural and functional unit of all living organisms 
• Cell Organelles are coordinated structures found in living cells that performs a specific function inside the cell.
• Organelles can be of two types
• Membrane-bound organelle - 
  • These are cell organelles that are enclosed by a membrane.
  • Example: Nucleus, chloroplast, Golgi apparatus, Mitochondria, peroxisome, lysosome, etc.
• Non membrane-bound organelle - 
  • These are cell organelles that are not enclosed by a membrane.
  • Example: Ribosomes, centrioles

Important Points

•  A lysosome is a single membrane-bound cell organelle.
• These contain hydrolytic enzymes that have the ability to break down different types of biomolecules.
• The hydrolytic enzymes present destroy any foreign material inside the cell such as bacteria or may also digest poorly working cell organelles.
• When a cell gets damaged and does not function properly, the lysosomes burst and the enzymes released digests off the own cell, ultimately leading to its death.
• Therefore they are known as "suicidal bags".

The correct answer is Tubulin.

Key Points

• A microtubule is comprised of tubulin proteins organized to frame an empty, straw-like cylinder, and each tubulin protein comprises two subunits, α-tubulin, and β-tubulin.
• Microtubules, similar to actin fibres, are dynamic designs: they can develop and shrivel rapidly by the expansion or expulsion of tubulin proteins.
• The tubulin proteins α-and β polymerize into long chains or fibres that structure microtubules, a fundamental component of the eukaryotic cytoskeleton.
• Tubulin dimers can depolymerize also as polymerize, and microtubules can go through quick patterns of gathering and dismantling.

Additional Information

• Ferritin is a blood protein that carries iron.
• Fibrinogen is a protein created by the liver.
• Elastin is quite possibly the most plentiful protein in your body.

Key Points

• Plastids are a type of cell organelle that are present in all plant cells and euglenoids.
• They are double membrane-bound organelles.
• They are considered to be important structures that have evolved to perform specific functions in a plant cell.
• Plastids are usually classified into different types on the basis of the pigments present in them.

Plastid Types - 

1. Chloroplast -
   • It contains chlorophyll pigment and performs photosynthesis in green plants and algae.
2. Chromoplast -
   • It contains fat-soluble carotenoid pigments like carotene, xanthophyll, etc. that gives a red, yellow or orange colour to the plant part.
   • It is thus present in the flowers and fruits of higher plants.
3. Leucoplast - 
   • These are the colourless plastids that lack any pigment.
   • They may be of various shapes and sizes.
   • Their major function is storage of nutrients.

Explanation:

• Leucoplasts can again be classified according to their storage material.
  • Amyloplast - Carbohydrates (starch)
  • Elaioplast - Oils and fats
  • Aleuroplast - Proteins
• In the given question, chloroplast has been related with its function i.e., photosynthesis.
• Similarly, leucoplast can be related with its own function, which is storage of food.

∴ Chloroplast : photosynthesis :: Leucoplast : Storage of food 

Concept:

• The plasma membrane is the outermost covering in animal cells and lies next to the cell wall in a plant cell.
• It is a selectively permeable membrane. 
• It permits hydrophobic molecules and small polar molecules to diffuse through the lipid layer but prevents ions and large polar molecules to diffuse through the membrane.
• The membrane maintains the shape of the cell and separates the contents of the cell from its surroundings.
• The plasma membrane also facilitates communication and signaling between the cells.

Important Points

Statement (i): CORRECT

• According to the Fluid Mosaic model of the plasma membrane, the plasma membrane is composed of lipids that are arranged in a bilayer of phospholipids.
• The components of the plasma membrane are phospholipids, proteins, carbohydrates, and cholesterol.
• These give a fluid appearance to the plasma membrane and make it flexible.
• The lipid component of the membrane mainly consists of phosphoglycerides.

Statement (ii): CORRECT

• The phospholipids have two ends polar heads and nonpolar tails.
• The polar heads are hydrophilic and present toward the outer sides.
• While the nonpolar tails are hydrophobic and present toward the inner sides.
• This ensures that the nonpolar tail of saturated hydrocarbons is protected from the aqueous environment.

Statement (iii): CORRECT

• The protein molecules in the plasma membrane are arranged in two ways depending on the ease of extraction.
• These are:
  • Extrinsic - Peripheral or extrinsic proteins lie on the surface of the membrane while integral or intrinsic proteins are partially or totally buried in the membrane.
  • Integral - Integral proteins form channels that permit the movement of large molecules and ions across the hydrophobic layer of the membrane.
• Peripheral proteins transport signals from one segment to the next of the membrane.

Thus, this statement is correct.

Statement (iv): INCORRECT

• The fluid mosaic model was proposed by Singer and Nicolson in 1972.
• They described the plasma membrane structure in the eukaryotic cells, and how it is arranged along with its components.

Concept:

• Endoplasmic reticulum: The network or reticulum of tiny tubular structures scattered in the cytoplasm is called the endoplasmic reticulum (ER).
• The ER divides the intracellular space into two distinct compartments, i.e., luminal (inside ER) and extraluminal (cytoplasm) compartments.
• The ER is of two types based on the presence or absence of ribosomes on its surface.
• The Endoplasmic reticulum bearing ribosomes on their surface is called Rough Endoplasmic Reticulum (RER) whereas in the absence of the ribosomes they appear smooth and are called Smooth Endoplasmic Reticulum (SER).
• Rough Endoplasmic Reticulum (RER) in the cells actively involved in the Synthesis of protein and secretion.
• The main function of Smooth Endoplasmic Reticulum (SER) includes transport of materials, Synthesis of lipid, and Synthesis of hormones.

​Explanation:

• The smooth endoplasmic reticulum (smooth ER) is a membranous organelle found in most eukaryotic cells. Its functions include 
• Synthesis of Lipids, including cholesterol and phospholipids.
• Steroid Hormones.
• Storage and metabolism of calcium ions within the cell.
• Detoxification of harmful metabolic byproducts/toxic substances.
• Glycogenolysis i.e the breakdown of the molecule glycogen into glucose.
• Thus, ''all are correct''.

​

Key Points

• Prokaryotic cells are unicellular organisms that lack a nucleus and other membrane-bound organelles in their cytoplasm.
• The genetic material of prokaryotic cells is present in a single circular chromosome that is not enclosed within a membrane.
• They are generally smaller in size than eukaryotic cells and have a simpler structure.
• They are found in bacteria and archaea, which are two of the three domains of life on Earth.

Additional Information

• Eukaryotic and Prokaryotic cells are the two main types of cells that make up living organisms.
• Here are the key differences between them:

The correct answer is Only I. 

Key Points

• Nuclear membrane is absent in prokaryotic cells.
• They do not contain a membrane bound nucleus and thus, their nucleus is called nucleoid.
• This a primitive adaptation.
• Eukaryotes contain membrane bound nucleus as well as membrane bound organisms.
• Plant cells additionally possess large, fluid-filled vesicles called vacuoles within their cytoplasm.

Additional Information Plant Cell

• The cell wall is the outermost rigid protective covering found only in the plant cell.
• Cell wall provides shape to plant cells.
• The plant cell is rectangular and comparatively larger than the animal cell.
• Cell membrane is the semi-permeable membrane that is present within the cell wall. It is composed of a thin layer of protein and fat.
• The nucleus is a membrane-bound structure that is present only in eukaryotic cells.
• Plastids  are membrane-bound organelles that have their own DNA.