Category: Cell Biology Objective Questions

Cell Biology Interview Questions and Answers for fresherson “Movement of Substances Across Cell Membranes”.

1. The transport of water molecules from a solution to the cell cytoplasm occurs in _________
A. Hypertonic solution
B. Hypotonic solution
C. Isotonic solution
D. All of the mentioned
Answer: B
Clarification: When the concentration of solute in the solution is greater than that of cell interior, it is called hypertonic solution. When the concentration of solute in the solution is greater than that of cell interior, it is called hypotonic solution. When both the solution and the cell interior has equal concentration of solute, it is called isotonic solution. Water diffuses from hypotonic solution towards cell interior with more solute concentration.

2. Plasmolysis occurs in __________
A. Hypertonic solution
B. Hypotonic solution
C. Both hypotonic and hypertonic solution
D. Isotonic solution
Answer: A
Clarification: If a plant cell is placed in a hypertonic medium, its volume shrinks as the water diffuses out of the cell through the cell wall. The plasma membrane pulls away from the surrounding cell wall. This process of loss of water is called as plasmolysis and it leads to loss of support and wilt.

3. Which of the following channels depend on forces such as stretch tension applied on the membrane?
A. Voltage-gated channels
B. Mechano-gated channels
C. Ligand-gated channels
D. Tension-gated channels
Answer: B
Clarification: The conformational change of mechano- gated channels depend on mechanical forces that are applied to the membrane. These mechanical forces such as stretch tension forces the channel to open the pathway for the transport of ions and solutes.

4. How many H⁺ ions are transported by the vacuole H+-ATPase pump and the vacuole H+-phosphatase pump per hydrolysis of ATP and pyrophosphate respectively?
A. 1, 1
B. 1, 2
C. 2, 1
D. 2, 2
Answer: C
Clarification: The vacuole H+-ATPase pump and the vacuole H⁺-phosphatase pump are membrane proteins on the vacuole membrane that helps in the active transport of H⁺ ions inside the vacuole. With the hydrolysis of one ATP molecule, two H⁺ ions can pass through the H⁺-ATPase pump. However, with the hydrolysis of one pyrophosphate molecule, one H⁺ ion can pass through the H+-pyrophospatase pump.

5. The ion most abundant in cells and most permeable to cell membrane is ____________
A. K⁺
B. Ca²⁺
C. Na⁺
D. H⁺
Answer: A
Clarification: K⁺ is the ion that is found in most abundance in cells. It also has the greatest permeability through cell membrane and as a result, it is pumped faster than any other ion through the cell membrane by active or passive transport.

6. Facilitative transporter ___________
A. Helps in facilitated diffusion
B. Changes conformation
C. Transports molecules passively
D. Changes conformation, transports molecules and facilitated diffusion
Answer: D
Clarification: Facilitated diffusion is a method by which molecules are diffused across the cell membrane with the help of an intermediate protein called facilitative transporter. The diffusing substance binds selectively to this membrane-spanning protein that facilitates in diffusion process. It undergoes conformational change, exposing the solute to the other surface of the membrane.

7. GLUT1 is an example of ______________
A. Channel protein
B. Facilitative transporter
C. Active transporter
D. Lipid-anchored protein
Answer: B
Clarification: Humans consist of membrane-spanning proteins that help in the transport of glucose molecules through the cell membrane. These molecules have five isoforms from GLUT1 to GLUT5. It facilitates the diffusion of glucose from the bloodstream into the cell through facilitated diffusion.

8. The ratio of Na⁺ and K⁺ transported by Na⁺/K⁺-ATPase pump is ___________
A. 1:1
B. 2:1
C. 2:3
D. 3:2
Answer: D
Clarification: The Na⁺/K⁺-ATPase pump facilitates the transport of sodium ions out of the cell, coupled with the transport of potassium ions into the cell. Three sodium ions are pumped out of the cell while two sodium ions are pumped into the cell.

9. Symport and Antiport is the classification of ____________
A. Primary active transport
B. Secondary active transport
C. Primary passive transport
D. Secondary passive transport
Answer: B
Clarification: Primary active transport involves hydrolysis of ATP or pyrophosphate or GTP to yied energy which helps in the transport of a particular molecule by utilization of that energy. Passive transport involves coupling the transport of one ion or molecule with the transport of another ion or molecule. It is of two types- Symport and Antiport. Symport refers to the pumping of two ions in the same direction of the cell membrane while Antiport refers to pumping of ions in the opposite direction.

10. Halobacterium salinarium uses the following for the active transport of ions to induce purple colour.
A. Light energy
B. ATP
C. Voltage
D. Chemical energy
Answer: A
Clarification: Halobacterium salinarium is a halophilic archaebacterium, which takes on a purple colour when grown under anaerobic conditions. This is due to the presence of bacteriorhodopsin, a proton pump which depends on light energy. The absorption of light in the retinal group of bacteriorhodopsin results in conformational change and a proton from the retinal group moves to the cell exterior.

11. During salt stress condition in Arabidopsis, which of the following antiport proteins are used?
A. AvPI and AtNHX
B. AvPI and AtDBF
C. AvPI and AvPII
D. None of the mentioned
Answer: A
Clarification: AvPI (Arabidopsis vacuola protein I) and AtNHX (Arabidosis transporting H⁺ ion) are the antiport proteins present on the membrane of vacuole. During salt stress condition, there is an increase in Na+ ion in the cell, which leads to acidity in cell and may be harmful to plants. These antiport transport Na⁺ ion into the vacuole from cytoplasm coupled with the transport of H⁺ ion from vacuole to cytoplasm. This result in reduction of Na+ concentration in cytoplasm and reduction of acidity in salt-stress condition.

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Cell Biology Multiple Choice Questions on “Chloroplast Function – CO2 Fixation and Carbohydrate Synthesis in CAM Plants”.

1. Which of the following plants undergo CAM photosynthesis?
A. Cactus
B. Sugarcane
C. Corn
D. Wheat
Answer: A
Clarification: CAM is known as crassulacean acid metabolism. These CAM plants fix CO₂ in the arid and hot climate regions.

2. The CAM pathway starts at daytime.
A. True
B. False
Answer: B
Clarification: The CAM pathway starts at night when there is lower temperature. This is due to the mechanism that reduces water loss by evatranspiration.

3. Where is the malate stored in CAM plants?
A. Chloroplast
B. Mitochondria
C. Vacuoles
D. Endoplasmic reticulum
Answer: C
Clarification: The CO₂ is converted to malate, a four carbon organic compound. This is stored in the vacuoles where it is later transported to the chloroplast for conversion of malate to CO₂ for photosynthesis.

4. How many aquatic plant genera can undergo CAM photosynthesis?
A. 4
B. 5
C. 6
D. 7
Answer: A
Clarification: The aquatic plants can also undergo CAM photosynthesis. There are about 4 genera of plants. They also follow the same pathway as the terrestrial CAM plants.

5. The CAM plants undergo daytime acidification and nighttime deacidification.
A. True
B. False
Answer: B
Clarification: During the nighttime, the plants take up CO₂ and convert it into organic acids called as acidification. While in daytime, they utilize the organic acids to form CO₂ back known as deacidification.

6. Which enzyme is used in converting bicarbonate ion to oxaloacetate?
A. Phosphoenolpyruvate reductase
B. Phosphoenolpyruvate hydrogenase
C. Phosphoenolpyruvate carboxylase
D. Phosphoenolpyruvate dehydrogenase
Answer: C
Clarification: The phosphoenolpyruvate carboxylase enzyme is used to catalyze bicarbonate to oxaloacetate and phosphate. This is one of the important mechanism in the carbon fixation in CAM plants.

7. Which enzyme is used to convert oxaloacetate to malate?
A. Malate dehydrogenase
B. Malate hydrolase
C. Malate carboxylase
D. Malate dehydratase
Answer: A
Clarification: Oxaloacetate is converted to malate by the enzyme malate dehydrogenase. The oxaloacetate obtains an electron from NAD+ and converts it to a four carbon compound malate.

8. Which of the following is a facultative CAM plant?
A. Century plant
B. Corn
C. Maize
D. Common ice plant
Answer: D
Clarification: Common ice plant is an facultative CAM plant. It usually does not undergo CAM photosynthesis but it undergoes CAM photosynthesis when it is under stress condition, like shortage of water, CO₂, etc.

9. How many molecules of ATP and NADPH₂ are used in synthesis of one glucose molecule?
A. 30 ATP and 10 NADPH₂
B. 10 ATP and 30 NADPH₂
C. 30 ATP and 12 NADPH₂
D. 12 ATP and 30 NADPH₂
Answer: C
Clarification: The CAM pathway uses 30 ATP and 12 NADPH₂ for synthesis of one glucose molecule. This is higher than the energy requirements of C4 and C3 cycles.

Cell Biology Multiple Choice Questions on “Chemical Basis of Life – Chaperones”.

1. What are molecular chaperones?
A. Enzymes
B. Cell mass
C. Tumor
D. Helper proteins
Answer: D
Clarification: Molecular chaperones are helper proteins that help unfolded or misfolded polypeptide chains to assume a certain folded state. The role of these proteins is to prevent the proteins from non-selectively interacting with other components in the cell.

2. Chaperones bind to which type of amino acids?
A. Charged
B. Uncharged
C. Hydrophobic
D. Hydrophilic
Answer: C
Clarification: The molecular chaperones also called the helper proteins attach to short stretches of hydrophobic amino acids which are exposed in nonnative proteins and are found deep within the core in a native protein.

3. Which of the following molecules bind to nascent polypeptides synthesized on the ribosomes?
A. Chaperonins
B. Hsp70
C. Hsp72
D. Hsp
Answer: C
Clarification: Hsp70 is a class of molecular chaperones that bind to nascent proteins being synthesized on ribosomes. Hsp70 chaperones prevent the newly synthesized proteins from binding to other proteins in the cytosol which could lead to misfolding or aggregation.

4. TriC is a _____________
A. hsp70
B. chaperonin
C. organelle
D. enzyme
Answer: B
Clarification: TriC is a chaperonin that helps stabilize long polypeptides. It contains chambers in which peptides can reside without any interference from the external environment.

5. Heat-shock response was first observed in which organism?
A. C. elegans
B. Drosophila
C. Arabidopsis
D. Bacteria
Answer: B
Clarification: Heat shock response on the form of production of heat shock proteins was first observed in Drosophila. In 1962, an Italian biologist was studying the development of Drosophila when it was observed that increasing the temperature, at which larvae grow new heat shock proteins appear on the chromosome.

6. Rubisco is a ________________
A. nucleic acid
B. protein
C. carbohydrate
D. fiber
Answer: B
Clarification: Rubisco is a protein found in chloroplasts of plant cells, it catalyzes the reaction in which carbon dioxide taken up from the atmosphere is covalently linked to organic molecules.

Cell Biology Multiple Choice Questions on “Nucleus – Structure and Function”.

1. Nucleoporins are __________
A. Nuclear pores
B. Ribosomes on nuclear membranes
C. rRNAs in the nucleolus
D. None of the mentioned
Answer: A
Clarification: The nuclear membrane is a double-layered membrane that is interrupted in places by the nuclear pores. The nuclear pores provide channels for the transport of molecules such as water, proteins, RNAs etc. The nuclear pores are collectively known as Nucleoporins.

2. The transport factors that help in the transport of molecules through the nuclear pores are known as ___________
A. Nucleopherins
B. Nucleoporins
C. Karyopherins
D. Karyoporins
Answer: C
Clarification: Proteins, ribosomal subunits, and some DNAs are transported through the pore complexes mediated by a family of transport factors known as karyopherins. Karyopherins are of two types- those that mediate movement of molecules into the nucleus are called importins and those that mediate movement out of the nucleus are called exportins.

3. Lamin proteins that bind to the intra-nuclear chromatin are _____________
A. Emerin
B. Nesprin
C. LEM-3
D. Cannot be said
Answer: C
Clarification: The nuclear lamina is mostly composed of lamin proteins. The cytosolic lamin proteins which face the cytoplasm, such as Emerin and Nesprin binds to the cytoskeleton to provide structural rigidity. Lamins such as LEM3 are found inside nucleus and form the nucleoplasmic veil and bind to the intra-nuclear chromatin.

4. Nuclear Organizer Regions (NOR) is found in ________
A. Nuclear matrix
B. Nucleolus
C. Nuclear lamina
D. Nucleoporins
Answer: B
Clarification: The nucleolus is a dense granular region present inside the nucleus. It is concerned with the production of rRNA and consists of tandems of rDNAs, DNA that codes for rRNA. These rDNA rich regions of nucleolus is called Nuclear Organizer Regions (NOR).

5. Cajal bodies mainly consist of the protein _________
A. Emerin
B. Actin
C. Coilin
D. Desprin
Answer: C
Clarification: Cajal bodies re sub-nuclear compact structures with diameter between 0.2-2.0 micrometers, depending on the species. Under electron microscope, the appear as small tangles threads with a dense dictricution of the Coilin protein. They are bound to the nucleolus by coilin proteins.

6. Which of the following is not a function of Cajal bodies?
A. snRNP biogenesis
B. histone mRNA processing
C. telomere assembly
D. tRNA processing
Answer: D
Clarification: Cajal bodies re sub-nuclear compact structures with diameter between 0.2-2.0 micrometers, depending on the species. They are mainly related to RNA synthesis and helps in RNA-related metabolic processes such as snRNPs biogenesis, maturation and recycling, histone mRNA processing and telomere maintenance.

7. Which of the following is also known as Kremer bodies?
A. Cajal bodies
B. PML bodies
C. Nuclear speckles
D. Nucleolus
Answer: B
Clarification: Promyelocytic leukaemia bodies (PML bodies) are spherical bodies that are found scattered throughout the nucleoplasm and are around 0.1–1.0 µm. They are also known by a number of different names such as nuclear domain 10 (ND10), Kremer bodies, PML oncogenic domains and also nuclear dots.

8. Which of the following plays a role in oncogenic function?
A. Kremer bodies
B. Cajal bodies
C. Splicing speckles
D. None of the mentioned
Answer: A
Clarification: Kremer bodies, also known as Promyelocytic leukaemia bodies (PML bodies) are spherical matrix-associated nuclear bodies. Their specific role in not yet known though their role in ongenesis and viral infection is unavoidable. They may be a site for RNA transcription, storage of rRNAs of other transcriptional activity.

9. Nuclear speckles ______________
A. perform splicing of snRNPs
B. perform splicing of rRNAs
C. act as a transcription site for rRNAs
D. act as a storage site for snRNPs
Answer: A
Clarification: Nuclear speckles, also called as splicing speckles are subnuclear structures that are enriched in pre-messenger RNA splicing factors and are located in the interchromatin regions of the nucleoplasm. The splicing factors help in the splicing of snRNPs and other splicing proteins that are necessary for pre-mRNA processing.

10. Which of the following is not true?
A. Paraspeckles are irregular shaped sub-nuclear compartments
B. Paraspeckles disappear in absence of RNA polemerase II transcription
C. They are transcription dependent
D. They are present during interphase and absent during mitosis.
Answer: D
Clarification: Paraspeckles are irregular shaped sub-nuclear compartments which are transcription dependent. Paraspeckles disappear in absence of RNA polemerase II transcription and all of its associated protein components form a crescent shaped perinucleolar cap in the nucleolus. However, paraspeckles are present during the interphase and all the stages of mitosis except the telophase.

Cell Biology Objective Questions & Answerson “Self-assembling Macromolecules”.

1. Tobacco Mosaic Virus consists of one long molecule of ______________
A. DNA
B. Carbohydrates
C. Glycerol
D. RNA
Answer: D
Clarification: In 1955 at the University of California, it was demonstrated that TMV particles consist of one long molecule of RNA which is 6600nucleotides long wound in a helical capsule made of 2130 identical protein subunits.

2. TMV particles are not capable of self-assembly.
A. True
B. False
Answer: B
Clarification: In the first experiments conducted in 1955, the RNA and protein components of a TMV were separated and then mixed together. After a brief incubation period, the recovered mixture contained infective particles. This confirmed the self-assembly property in TMV.

3. Ribosomes consist of RNA and _____________
A. carbohydrates
B. nucleic acids
C. proteins
D. nucleotides
Answer: C
Clarification: Ribosomes consist of different types of RNAs and proteins. Regardless of the source, all ribosomes contain two subunits of different sizes.

4. The large (50S) ribosomal subunit of bacteria contains _______ molecules of RNA.
A. 1
B. 2
C. 3
D. 4
Answer: B
Clarification: The large (50S) ribosomal subunit of bacteria contains 2 molecules of RNA and approximately 32 different proteins. The smaller 30S subunit contains one RNA molecule and 21 different proteins.

5. Which protein of the smaller subunit of bacterial ribosome was found to have a function in ribososme assembly?
A. S12
B. S14
C. S16
D. S18
Answer: C
Clarification: The S16 protein of the smaller ribosomal subunit 30S was found to have a function solely in ribosome assembly. The deletion of this protein slowed down the in vitro assembly process.

6. Eukaryotic subunits are not capable of self-assembly.
A. True
B. False
Answer: A
Clarification: Ribosomal subunits of bacteria are capable of self-assembly whereas those of eukaryotes are not. Transient association of proteins is required in the in vitro synthesis of eukaryotic ribosomes that don’t even end up in the final product.

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