Cell and Cell Theory MCQ Quiz in मल्याळम - Objective Question with Answer for Cell and Cell Theory - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

The correct answer is II only

Explanation:

I. A cell contains mainly of a cell wall, plasma membrane, and cytoplasm only.

• This statement is incorrect. These components are present in many cell types particularly in plants, bacteria, and fungi. Animal cells do not have a cell wall, and cells have many other important organelles like the nucleus, mitochondria, etc.

II. Mycoplasma is the smallest cell in size.

• This statement is correct. Mycoplasma is among the smallest known cells, with some species as small as 0.3 μm in length.

III. The cell membrane of human RBC is composed of 40% proteins and 52% lipids.

• This statement is incorrect. In human beings, the membrane of the erythrocyte has approximately 52 percent protein and 40 percent lipids.

IV. Study of a cell is known as mycology.

• This statement is incorrect. The study of cells is called cytology. Mycology is the study of fungi.

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 Infolding of outer mitochondrial membrane

Concept:

• Cristae are the internal compartments formed by the inner membrane of mitochondria. They play a crucial role in cellular respiration and energy production.
• The primary function of cristae is to increase the surface area of the inner mitochondrial membrane where critical processes like oxidative phosphorylation occur.
• Cristae are rich in proteins and enzymes essential for the electron transport chain and ATP synthesis.

Explanation:

• Contains oxysome: Oxysomes, also known as F1 particles or ATP synthase complexes, are present on the cristae. They play a crucial role in the synthesis of ATP during cellular respiration.
• Have elementary particles: Elementary particles, synonymous with oxysomes or F1 particles, are indeed found on the cristae and are essential for the production of ATP.
• Increases surface area of inner membrane: The cristae significantly increase the surface area of the inner mitochondrial membrane, facilitating more space for the electron transport chain and ATP synthesis to occur.
• Infolding of outer mitochondrial membrane: This is incorrect. The cristae are infoldings of the inner mitochondrial membrane, not the outer membrane.

• Cells are the structural and functional units of life.
• All living organisms are composed of cells that arise from pre-existing cells.
• Each cell contains a dense membrane-bound structure called a nucleus that contains genetic materials.
• Both prokaryotic and eukaryotic cells have a semi-fluid matrix occupying the cell's volume called cytoplasm.
• The cell's functioning contains different types of cell organelles, viz. mitochondria, ribosomes, vacuoles, endoplasmic reticulum, Golgi bodies, lysosomes, microtubules, etc.
• The cell membrane and cell wall protect the cell organelles and maintain the shape and size of the cells.

Important PointsLysosomes - 

• Lysosomes are membrane-bound vesicular structures formed by the process of packaging in the Golgi apparatus.
• Lysosomes contain almost all types of hydrolytic enzymes.
• These enzymes are optimally active at the acidic pH.
• The enzymes may be used to destroy invading foreign particles such as viruses, bacteria, etc., thus fighting against infection inside the cell.
• The hydrolytic enzymes are capable of digesting carbohydrates, lipids, proteins, etc.

Mitochondria - 

• This is a sausage-shaped or cylindrical cell organelle having a double membrane.
• Mitochondria are the sites of aerobic respiration.
• They produce cellular energy in the form of ATP, thus they are called the 'Power house' of the cell.

Cell wall - 

• The cell wall is a non-living rigid structure forming an outer covering for the plasma membrane of algae, fungi, and plants.
• It gives shape and rigidity to the cell and protects cells from mechanical damage and infections.
• The cell wall helps in cell-to-cell interactions and provides a barrier to undesirable macromolecules.

Ribosomes - 

• Ribosomes are the granular structures that are scattered in the cytoplasm or attached to the endoplasmic reticulum forming Rough endoplasmic reticulum.
• They are composed of ribonucleic acids and proteins and are not surrounded by any membrane.
• These are actively associated with protein synthesis and secretion.
• Thus, ribosomes are known as the 'Protein factory' of cells.

Vacuoles - 

• The vacuoles are the membrane-bound spaces found in the cytoplasm.
• In plant cells, vacuoles can occupy 90% of the volume of the cell.
• It stores nutrients, water, and sap.
• Also contains excretory products and other materials not useful for the cell.

Corrected Table:

Hence, the correct answer is option 2: (A)-(iv), (B)-(i), (C)-(v), (D)-(ii), (E)-(iii).

The correct answer is Aerobic respiration.

Explanation-

Mitochondria are often called the "powerhouse" of the cell since they are responsible for aerobic cellular respiration, a series of metabolic reactions that convert biochemical energy from nutrients into adenosine triphosphate (ATP), which can then be used by the cell for numerous processes.

Aerobic respiration involves four key steps: glycolysis, pyruvate decarboxylation, Krebs cycle (or citric acid cycle), and the electron transport chain.

• Glycolysis occurs in the cytoplasm of cells, the pyruvate produced in glycolysis is transported into the mitochondria where the rest of the processes occur. Here's a brief overview of what happens within the mitochondria:
• Pyruvate Decarboxylation: This occurs in the matrix of the mitochondria. Each pyruvate molecule from glycolysis is decarboxylated, meaning one of its carbon atoms is removed. This carbon atom is then released as a molecule of carbon dioxide. The remaining two-carbon molecule is then oxidized, and its electrons are transferred to a molecule called Nicotinamide Adenine Dinucleotide (NAD+) to create NADH - an energy-carrying molecule. The final product of the reaction is a molecule called Acetyl Coenzyme A (Acetyl-CoA).
• Krebs Cycle (Citric Acid Cycle): This also occurs in the mitochondrial matrix and involves a series of chemical reactions used by all aerobic organisms to release stored energy. The Acetyl-CoA produced from Pyruvate Decarboxylation enters the cycle. Over the course of the cycle, the Acetyl-CoA is broken down and more carbon dioxide is released. The output of the Krebs Cycle for each Acetyl-CoA molecule includes 2 CO₂ molecules, 3 NADH molecules, 1 FADH₂ molecule (another type of energy-carrying molecule) and 1 ATP molecule.
• Electron Transport Chain: This happens across the inner mitochondrial membrane. The NADH and FADH₂ produced in earlier steps donate their electrons to an electron transport chain, which uses this electron flow to pump protons (H+) out of the matrix and into the intermembrane space. This creates a proton gradient.
• Chemiosmosis and Oxidative Phosphorylation: Returning to the matrix, driven by the gradient, protons pass through a protein complex called ATP synthase. The energy released by this allows ATP synthase to bind ADP to inorganic phosphate, forming ATP. At the end of the electron transport chain, electrons bind with these protons and ambient oxygen to form water.

In summary, the mitochondria make use of the products from glycolysis in the cytoplasm and run the reactions of pyruvate decarboxylation, the Krebs cycle, and the electron transport chain to produce ATP, releasing carbon dioxide and water as waste products in the process.

Additional Information 

Mitochondria are small, spherical or rod-shaped organelles that are surrounded by two membranes, each a phospholipid bilayer with embedded proteins.

• Outer Mitochondrial Membrane: This is a porous membrane and very permeable due to protein structures called porins. It allows small molecules and ions to freely diffuse from the cytosol into the intermembrane space.
• Intermembrane Space: This is the region between the outer and inner membranes. It has an important role in the primary function of mitochondria, which is oxidative phosphorylation. The concentration of proteins here is similar to the concentration in the cytosol. It also contains enzymes that use ATP passing out of the matrix to phosphorylate other nucleotides.
• Inner Mitochondrial Membrane: This is highly impermeable to all molecules. It folds over many times to form crest-like structures called cristae which increases the surface area of the membrane and therefore its ability to produce ATP. This membrane also has transport proteins that move proteins from the intermembrane space into the matrix. The electron transport chain and ATP synthase are located in the inner membrane.
• Matrix: This is the space enclosed by the inner membrane. It contains dozens of enzymes, including those required for the oxidation of pyruvate and fatty acids, and for the citric acid cycle (also known as the Krebs cycle or TCA). The mitochondrial DNA, ribosomes, and additional enzymes necessary for the expression of this DNA are all found within the matrix.

Mitochondria are unique because they have their own DNA, distinct from the nuclear DNA of the cell.

Conclusion-  Mitochondria are sites of aerobic respiration.

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 Tonoplast.

Explanation-

• The membrane that surrounds the vacuole of a plant cell is indeed called the tonoplast.
• The tonoplast is a type of cellular membrane that selectively controls the flow of molecules between the cytosol and the interior of the vacuole.
• This membrane plays a central role in maintaining the osmotic balance and turgor pressure of cell, which is the force exerted by water pushing the plasma membrane against the cell wall.
• The tonoplast also isolates harmful materials that could potentially impair the rest of the cell.
• The tonoplast contains a variety of proteins that are involved in transporting solutes across the membrane, as well as channels for water (aquaporins).
• Tonoplast aids in the regulation of ion balance, pH, and other aspects of metabolism within the cell. It's a crucial part of the cell's ability to adapt to changing environmental conditions.

Additional Information 

Plasmalemma: This is another term for the cell or plasma membrane. It's a biologically active boundary between the living cell and its surroundings that provides selective permeability. It's composed of a phospholipid bilayer intertwined with proteins and carbohydrates. The primary job of the plasmalemma is to regulate the exchange of materials such as ions and molecules into and out of the cell.

Cell Membrane: As mentioned, the cell membrane (also termed as plasma membrane or plasmalemma) is the cell's outermost line of defense against its surroundings. It controls the movement of substances in and out of cells, houses cytoplasm, and includes a variety of biological molecules, primarily lipids and proteins. This membrane helps maintain homeostasis within the cell and serves as a communication interface with other cells and the extracellular environment.

Middle Lamella: The middle lamella is a thin layer that is located between primary walls of plant cells. It's the first layer that forms during cell division, and it cements the cells together.The middle lamella is chiefly composed of pectic compounds, including calcium pectate and magnesium pectate. Middle lamella is not present in animal cells, it's specific to plants, algae, and some fungi.

Conclusion- The membrane that encloses a vacuole is called Tonoplast.

Explanation:

• Guard cells: Guard cells are specialized cells found in the epidermis of a leaf. They surround and regulate the opening and closing of stomata, which are tiny pores present on the leaf's surface. The stomata are responsible for gas exchange, allowing carbon dioxide to enter the leaf for photosynthesis and releasing oxygen and water vapor. Therefore, guard cells are indeed found in the section of a leaf.
• Stoma: As mentioned above, stomata are small pores present in the epidermis of a leaf. They allow the exchange of gases between the leaf and the atmosphere. Stomata are surrounded by the guard cells that regulate their opening and closing. Thus, stomata are indeed found in the section of a leaf.
• Chlorophyll: Chlorophyll is the green pigment found in chloroplasts, which are organelles within plant cells responsible for photosynthesis. Chloroplasts are mainly found in the mesophyll cells of a leaf, which are located between the upper and lower epidermis. Chlorophyll plays a crucial role in capturing light energy to facilitate photosynthesis. Therefore, chlorophyll is indeed found in the section of a leaf.
• Pseudopodia: Pseudopodia are temporary projections of the cytoplasm in certain eukaryotic cells, such as amoebas, used for locomotion and capturing prey. However, pseudopodia are not found in the section of a leaf. They are specific to certain single-celled organisms and not a feature of plant cells.
• Xylem: Xylem is a type of tissue in vascular plants that transports water and some nutrients. While the xylem is found in the plant's stem and root, it doesn't directly exist in the leaf structure, though leaf veins contain extensions of the stem's xylem. So it's a bit more ambiguous.

Therefore the correct answer is pseudopodia and Xylem are not found in the section of a leaf. They are a feature of certain single-celled organisms and are not part of the leaf's structure.

The correct answer is All of the above

Concept:

• The endoplasmic reticulum (ER) is a critical cellular organelle involved in various functions essential for cell survival and operation. It exists in two forms: rough ER (RER) and smooth ER (SER).
• Rough ER has ribosomes attached to its surface, which are sites for protein synthesis.
• Smooth ER, on the other hand, lacks ribosomes and is involved in lipid synthesis and detoxification processes.

Explanation:

• Mechanical Support: The endoplasmic reticulum provides structural support to the cell by maintaining its shape and providing a scaffold that helps in the organization of the cell’s internal components.
• Lipoproteins and Glycogen Production: The smooth ER is involved in the synthesis of lipids, including phospholipids and cholesterol, which are essential for the formation of cell membranes and lipoproteins. Additionally, it plays a role in the metabolism of carbohydrates, including the conversion and storage of glycogen.
• Translocation: The rough ER is involved in the translocation of newly synthesized proteins. These proteins are either destined for secretion or for use within the cell membrane. The ER ensures that proteins are correctly folded and modified before they are transported to their final destinations.

The correct answer is Golgi apparatus 

Explanation:

The Golgi apparatus is a key organelle involved in the processing, modification, and packaging of macromolecules, including polysaccharides, proteins, and lipids.

• The Golgi apparatus is composed of stacks of membrane-bound cisternae, often referred to as Golgi stacks.
• It plays a crucial role in the modification, sorting, and packaging of proteins and lipids that are synthesized in the endoplasmic reticulum (ER).
• The Golgi apparatus is involved in the synthesis and modification of polysaccharides, which are then secreted or incorporated into the cell membrane or cell wall (in plants and fungi). This includes adding carbohydrate moieties to proteins (glycosylation) and modifying existing polysaccharides.
• It receives proteins from Endoplasmic Reticulum. It packages it into membrane-bound vesicles, which are then transported to various destinations, such as lysosomes, plasma membrane or secretion.
• Once modified, polysaccharides and other macromolecules are enclosed in vesicles that bud from the Golgi and are transported to their final destinations, including the cell surface for secretion.