Maharashtra BoardEnglish MediumSTD 11 ScienceBiologyCell Structure and Organization3 Marks
Question
Give the functions of plasma membrane.
✓
Answer
$1.$ The significant function of plasma membrane is transport of molecules across it. Plasma membrane is selectively permeable.
$2.$ Passive transport:
$a.$ Many molecules move across the membrane without spending energy.
$b.$ Some molecules move by simple diffusion along the concentration gradient i.e. from higher to lower concentration.
$c.$ Neutral molecules may move across the membrane by the process of simple diffusion.
$d.$ Water may also move by osmosis.
$3.$ Active transport:
$a.$ Few ions or molecules are transported against concentration gradient i.e. from lower to higher concentration.
$b.$ This requires energy, hence $\text{ATP}$ is utilized. As such a transport is an energy dependent process in which $\text{ATP}$ is utilized, it is called Active transport e.g. $Na^+ /K^+$ pump.
$c.$ Polar molecules cannot pass through non$-$polar lipid bilayer. Therefore, they require carrier proteins to facilitate their transport across the membrane.
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