11. Number of covalent bonds formed by nitrogen is A) 1 8)2 C)3 D)4 E)5 12. Aqua

Question

11. Number of covalent bonds formed by nitrogen is A) 1 8)2 C)3 D)4 E)5 12. Aquaporins are A) holes in phospholipid bilayer 8) channel protein C) carrier protein 13. The control of solute concentrations and water balance in Paramecium is D) none of these A) osmoregulation B) plasmolysis C)osmosis D) all of these 14. The diffusion of ions across a membrane is along A) electrical gradient B) concentration gradient C) electrochemical gradient D) none of these 15. Small channels between plant cells A) gap junction B) stomata C) desmosome D) plasmod 16. Cell-cell recognition is due tomolecule in cell membrane esmata A) cholesterol B) protein C) phospholipid D) branched sugar chain 17. Small part of enzyme comes in direct contact with substrate A) active site B) allosteric site C) inhibition site D) activation site 18. B-Pleated representsstructure in proteins A) primary B) secondary Ctertiary D) none of these 19. A RBC placed in 1.2% NaCl solution A) same size B) get bigger C) shrinks D) all of these 20. No membrane bound organelle assembles ribosomal units Ajlysosome B)peroxisome C) nucleolus D) centrosome

Explanation / Answer

11. Number of covalent bonds formed by nitrogen-3

Nitrogen has 5 valence electrons. This means it needs 3 electrons to complete its octet, thus forming 3 covalent bonds i.e. triple bond. One of the strongest bonds known are that of nitrogen. Nitrogen is more stable due to this bond.

12. Aquaporins are channel proteins which help in transport of water between cells. Water flows more rapidly through aquaporins than through the phospholipid bilayer.

13. The control of solute concentrations and water balance in Paramecium is through osmoregulation. This is a necessary adaptation for fresh water and salty water life forms. Paramecium-which is hypertonic to pond water has a contractile vacuole that acts as a pump to remove the excess water that has been accumulated due to osmosis.

15. Small channels between plant cells- Plasmodesmata. These enable transport and communication between cells.

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