Cell-Biology Miscellaneous


  1. Choose the CORRECT sequence of steps involved in cytoplast production.









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    Digestion of cell wall → protoplast viability → cybrid formation → osmotic stabilizer

    Correct Option: B

    Digestion of cell wall → protoplast viability → cybrid formation → osmotic stabilizer


  1. Which one of the following statements regarding G proteins is INCORRECT?









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    All G proteins are not trimeric. GPCR dimerization also was proposed to participate in arrestin-mediated desensitization based on the size of the cytoplasmic tip of rhodopsin and the presence of two cup-like domains in arresting both of which were implicated in receptor binding which one arrestin binds to two receptors in a dimer.

    Correct Option: C

    All G proteins are not trimeric. GPCR dimerization also was proposed to participate in arrestin-mediated desensitization based on the size of the cytoplasmic tip of rhodopsin and the presence of two cup-like domains in arresting both of which were implicated in receptor binding which one arrestin binds to two receptors in a dimer.



  1. In a typical mitotic cell division cycle in eukaryotes, M phase occurs immediately after the









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    G2 phase, or Gap 2 phase, is the third and final subphase of Interphase in the cell cycle directly preceding mitosis. It follows the successful completion of S phase, during which the cell's DNA is replicated. G2 phase ends with the onset of prophase, the first phase of mitosis in which the cell's chromatin condenses into chromosomes.

    Correct Option: D

    G2 phase, or Gap 2 phase, is the third and final subphase of Interphase in the cell cycle directly preceding mitosis. It follows the successful completion of S phase, during which the cell's DNA is replicated. G2 phase ends with the onset of prophase, the first phase of mitosis in which the cell's chromatin condenses into chromosomes.


  1. ATP biosynthesis takes place utilizing the H+ gradient in mitochondria and chloroplasts. Identify the correct sites of H+ gradient formation.









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    During chemiosmosis, the free energy from the series of reactions that make up the electron transport chain is used to pump hydrogen hydrogenions across the membrane, establishing an electrochemical gradient. Hydrogen ions in the matrix space can only pass through the inner mitochondrial membrane through a membrane protein called ATP synthase.
    ATP synthesis in chloroplasts is very similar to that in mitochondria: Electron transport is coupled to the formation of a proton (H+) gradient across a membrane. The energy in this proton gradient is then used to power ATP synthesis. Two types of processes that contribute to the formation of the proton gradient are:
    (a) processes that release H+ from compounds that contain hydrogen, and
    (b) processes that transport H+ across the thylakoid membrane.

    Correct Option: B

    During chemiosmosis, the free energy from the series of reactions that make up the electron transport chain is used to pump hydrogen hydrogenions across the membrane, establishing an electrochemical gradient. Hydrogen ions in the matrix space can only pass through the inner mitochondrial membrane through a membrane protein called ATP synthase.
    ATP synthesis in chloroplasts is very similar to that in mitochondria: Electron transport is coupled to the formation of a proton (H+) gradient across a membrane. The energy in this proton gradient is then used to power ATP synthesis. Two types of processes that contribute to the formation of the proton gradient are:
    (a) processes that release H+ from compounds that contain hydrogen, and
    (b) processes that transport H+ across the thylakoid membrane.



  1. Apoptosis is characterized by









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    Programmed cell death (PCD) is a death of a cell in any form, mediated by an intracellular program. PCD is carried out in a regulated process which usually confers advantage during an organisms life cycle. PCD also serves an important function during both plant and metazoan (multicellular animals) tissue development. Apoptosis is a form of programmed cell death. However, necrosis is a non physiological process that occurs as a result of infection or injury.

    Correct Option: B

    Programmed cell death (PCD) is a death of a cell in any form, mediated by an intracellular program. PCD is carried out in a regulated process which usually confers advantage during an organisms life cycle. PCD also serves an important function during both plant and metazoan (multicellular animals) tissue development. Apoptosis is a form of programmed cell death. However, necrosis is a non physiological process that occurs as a result of infection or injury.