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The cell membrane is semi permeable in nature, that is, it allows the passage of some substances while it disallows some substances. Small and non polar molecules pass quite easily through the cell membrane but large and polar molecules can not do this. 
The substances which can easily pass through the cell membranes make use of passive transports such as diffusion and facilitated diffusion to enter the cells while substances which can not pass through the cell membranes on their own make use of active transport. Examples of active transport are endocytosis and ectocytosis, 

The cell membrane is semi-permeable and allows the molecule by several methods:

  • Simple diffusion
  • Passive transport
  • Active transport

Further Explanation:

The cell membrane has an ability to control the flux of ions, amino acids, and gases through a lipid bilayer. The lipid bilayer is made up of phospholipids, and these membranes have hydrophobic interior, a layer is selectively permeable and allows only small, non-polar molecules. A large and polar bit like glucose can’t cross the plasma membrane easily; they require energy and carrier protein to transport. The transport of molecules can either be active or passive transport. Passive transport refers to the movement of the ions or other molecules across the membrane without any input of the energy.  

Types of transport:

  • Passive transport
  • Active transport

Passive transport can be of 3 types:

  • Simple diffusion
  • Facilitated diffusion
  • Osmosis

The process of diffusion is the movement of a molecule or substance from a higher concentration of an area to a lower concentration area. Mostly diffusion occurs in gases and liquid. The concentration gradient is referred to as to the difference in the concentration of the substance. The process of Diffusion ceases when the concentration of molecule or substance is equal in both regions.

In passive transport, the movement of ion or small molecule according to their concentration gradient occurs from higher concentration to the lower concentration. But large polar molecule or charged molecule, for example, glucose, Na+ requires carrier protein to transport charged molecule across the membrane; they do not require ATP or energy to transport. In active transport, they require ATP as well as a carrier protein to transport molecules across the plasma membrane, an example of active transport is a sodium-potassium pump.

Learn more:

  1. Learn more about cell membrane https://brainly.com/question/5923583  
  2. Learn more about cell cycle https://brainly.com/question/1600165
  3. Learn more about diffusion https://brainly.com/question/1386629

Answer: Details

Grade: High School  

Subject: Biology

Chapter: Cell membrane

Keywords:

Active transport, passive transport, facilitated transport, diffusion, cell membrane, ions, molecule, glucose.

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