12. The signal transduction cascade in a sensory cell of the olfactory system in
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12. The signal transduction cascade in a sensory cell of the olfactory system in humans a. is initiated when an odorant binds to a specific receptor protein in the olfactory cilia of the sensory cell b. involves adenylyl cyclase, which catalyzes the synthesis of cyclic AMP c. leads to hyperpolarization of the plasma membrane of the sensory cell following the binding of cyclic AMP to sodium channels in the membrane d. all of the above e. a and b, but not c 13. Based on the discussion in lecture, which of the following statements about the visual system is FALSE? a. Rhodopsin consists of both an opsin protein and a light-absorbing component. b. When all-trans-retinal absorbs a photon of light energy, it changes to 11-cis-retinal, which in turn results in a change in the conformation of opsin c, when cyclic GMP is converted by phosphodiesterase into 5'-GMP, it leads to the closing of sodium channels in the outer plasma membrane of a rod cell d. When rhodopsin is activated by the absorption of light energy, it activates transducin (a G protein) in the disc plasma membrane 14. Macular degeneration results primarily from a. a breakdown in the structure of the crystalline proteins that form the len:s b. damage to the optic nerve c. a breakdown in the structure of the cornea. d. none of the above 15. In the cerebral cortex, information from the OLFACTORY system is received and processed in the olfactory bulb associated with the a. frontal lobe b. occipital lobe c. temporal lobe d. none of the above 16. In a sexual life cycle involving the alternation between haploid and diploid phases a. meiosis gives rise to the haploid phase b. the product of fertilization is a diploid zygote c. the gametes are haploid. d. all of the above e. b and c, but not a 17. Which of the following statements about the sexual life cycle of gymnosperms is FALSE? a. Gymnosperms are homosporous b. The multicellular female gametophyte is dependent for its nutrition on the multicellular sporophyte c. Megaspores give rise via mitosis to multicellular female gametophytes 18. In the sexual life cycle of angiosperms, a. the generative cell divides mitotically to produce two haploid sperm. b. the embryo sac is the multicellular female gametophyte c. the diploid megasporocyte undergoes meiosis to give rise to four haploid megaspores, one of which survives. d. all of the above e. b and c, but not aExplanation / Answer
12. A) Signal transduction starts when odorent molecules bind with specific receptor protein in the olfactory cilia of sensory cell. Action potential generates and membrane depolarise. Neurotransmitters are released and brain gets message about the presence of food.
13. Option B is false. As 11-cis retinol absorb a photo of the light energy it changes to all trans retinol and change confirmation of opsin.
15.a) Olfactory bulb located near frontal lobe where information from olfactory lobe is received and processed.
16. Option D. Somatic cell is diploid(2n). Via meiosis gametes are produced which are haploid(n). One gamete(n) is fused with another gamete(n)[each comes from father and mother] during fertilization and gives diploid zygote (2n).
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