Question

41. Phospholipids are amphipathic molecules a. True 42. Which of the following structure's protect a plant cell from bursting due to the uptake of excess water? b. False a. Mitochondria b. Plasma membrane c. Chloroplast 43. The opening of d. Cell wall channels is controlled by the binding of a substance to the channel. a. Mechanically-gated c. Voltage-gated b. Ligand-gated d. DNA 44. The concentration of Ca' is in the cell, but outside of the cell. c. Higher .... Lower c. Equal ...... Equal d. Lower .... Higher d. None of the above 45. protein is a major component of the cell cortex in RBCs, that provide support to the cell membrane and maintain cell shape. a. Scramblase c. Glycocalyx b. Spectrin d. Porins 46. As Cl" ions flow down their concentration gradient: a. The inside of the cell becomes more positive b. The inside of the cell becomes more negative c. The outside of the cell becomes more negative d. The membrane potential is not affected 47. As Ca ions flow down their concentration gradient a. The inside of the cell becomes more positive b. The inside of the cell becomes more negative c. The outside of the cell becomes more positive d. The membrane potential is not affected 48. Integral membrane proteins are not amphipathic a. True b. False 49. Ca pump move Ca ions from the of the cell to the of the cell a. Interior .... Exterior c. Both choices are true b. Exterior .... Interior 50. Na+/K* pump move Na+ to the _ of the cell and K+ to the of the cell c. Interior .... Exterior a. Interior .... Interior d. Exterior .... Interior b. Exterior .... Exterior

Answer 1

41. True

Phospholipid are molecules made up of phosphate and lipids. Lipids are esters of glycerol and fatty acids. Lipids are hydrophobic molecules where as phosphate is a hydrophilic molecule. In lipids, fatty acids form the long hydrophobic tails where as phosphate is the hydrophilic head in phospholipids. Therefore because of the presence of both hydrophilic and hydrophobic molecules, phospholipids are called as amphipathic molecules.

42. D

Cell wall is protective outermost covering of plant cell which helps the cell to maintain its shape and protect the cell from bursting. It is made up of cellulose in plants.

Plasma membrane is a phospholipid bilayer which is involved in selective transportation of molecules across cell surface.

Chloroplast is the site of photosynthesis in plants which takes up solar energy, atmospheric carbon dioxide and water to synthesize sugar molecule along with the release of oxygen.

Mitochondria is the site of cellular respiration and all the living organisms. It uses glucose in and breakdown it in the presence of oxygen to yield carbon dioxide, water and ATP molecules.

43. B

Channels are the transmembrane proteins which open and closed in response to an external stimulus. These are also called as gated proteins because of their opening and closing. The channels which open and close with respect to the binding of a ligand are called as arrogant gated channels. The channels which open and close with respect to voltage change are called as voltage gated channel.

44. D

In all the cells, cytosolic calcium ion is maintained at a very low concentration. This occurs by actively pumping out the calcium ions which enter the cell from extracellular Matrix and other sources.

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