Question

why is plasma membrane called semi permiable membrane. long answer​

Answer 1

Answer:

The plasma membrane is called a selectively permeable membrane as it permits the movement of only certain molecules in and out of the cells. Not all molecules are free to diffuse. If plasma membrane ruptures or breaks down then molecules of some substances will freely move in and out of the cells. As the plasma membrane acts as a mechanical barrier, the exchange of material from its surroundings through osmosis or diffusion in a cell won’t take place. Consequently, the cell would die due to the disappearance of the protoplasmic material. It allows hydrophobic molecules and small polar molecules diffuse through the lipid layer, but does not allow ions and large polar molecules cannot diffuse through the membrane.

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Answer 2

ᴛʜᴇ ᴍᴇᴍʙʀᴀɴᴇ ᴛʜᴀᴛ sᴜʀʀᴏᴜɴᴅs ᴛʜᴇ ᴏʀɢᴀɴᴇʟʟᴇs ᴏғ ᴛʜᴇ ᴄᴇʟʟ, ʙʏ ᴄʀᴇᴀᴛɪɴɢ ᴀ ʙᴀʀʀɪᴇʀ ʙᴇᴛᴡᴇᴇɴ ᴄᴇʟʟ ᴏʀɢᴀɴᴇʟʟᴇs ᴀɴᴅ ᴛʜᴇ ᴇxᴛᴇʀɴᴀʟ ᴇɴᴠɪʀᴏɴᴍᴇɴᴛ ɪs ᴄᴀʟʟᴇᴅ ᴛʜᴇ ᴘʟᴀsᴍᴀ ᴍᴇᴍʙʀᴀɴᴇ. ɪᴛ ɪs ᴀʟsᴏ ᴄᴀʟʟᴇᴅ ᴀ ʙᴏᴜɴᴅᴀʀʏ ᴏғ ᴛʜᴇ ᴄᴇʟʟ.ᴛʜᴇ ᴘʟᴀsᴍᴀ ᴍᴇᴍʙʀᴀɴᴇ ɪs ᴄᴀʟʟᴇᴅ ᴀ sᴇʟᴇᴄᴛɪᴠᴇʟʏ ᴘᴇʀᴍᴇᴀʙʟᴇ ᴍᴇᴍʙʀᴀɴᴇ ᴀs ɪᴛ ᴘᴇʀᴍɪᴛs ᴛʜᴇ ᴍᴏᴠᴇᴍᴇɴᴛ ᴏғ ᴏɴʟʏ ᴄᴇʀᴛᴀɪɴ ᴍᴏʟᴇᴄᴜʟᴇs ɪɴ ᴀɴᴅ ᴏᴜᴛ ᴏғ ᴛʜᴇ ᴄᴇʟʟs. ɴᴏᴛ ᴀʟʟ ᴍᴏʟᴇᴄᴜʟᴇs ᴀʀᴇ ғʀᴇᴇ ᴛᴏ ᴅɪғғᴜsᴇ. ɪғ ᴘʟᴀsᴍᴀ ᴍᴇᴍʙʀᴀɴᴇ ʀᴜᴘᴛᴜʀᴇs ᴏʀ ʙʀᴇᴀᴋs ᴅᴏᴡɴ ᴛʜᴇɴ ᴍᴏʟᴇᴄᴜʟᴇs ᴏғ sᴏᴍᴇ sᴜʙsᴛᴀɴᴄᴇs ᴡɪʟʟ ғʀᴇᴇʟʏ ᴍᴏᴠᴇ ɪɴ ᴀɴᴅ ᴏᴜᴛ ᴏғ ᴛʜᴇ ᴄᴇʟʟs. ᴀs ᴛʜᴇ ᴘʟᴀsᴍᴀ ᴍᴇᴍʙʀᴀɴᴇ ᴀᴄᴛs ᴀs ᴀ ᴍᴇᴄʜᴀɴɪᴄᴀʟ ʙᴀʀʀɪᴇʀ, ᴛʜᴇ ᴇxᴄʜᴀɴɢᴇ ᴏғ ᴍᴀᴛᴇʀɪᴀʟ ғʀᴏᴍ ɪᴛs sᴜʀʀᴏᴜɴᴅɪɴɢs ᴛʜʀᴏᴜɢʜ ᴏsᴍᴏsɪs ᴏʀ ᴅɪғғᴜsɪᴏɴ ɪɴ ᴀ ᴄᴇʟʟ ᴡᴏɴ’ᴛ ᴛᴀᴋᴇ ᴘʟᴀᴄᴇ. ᴄᴏɴsᴇǫᴜᴇɴᴛʟʏ, ᴛʜᴇ ᴄᴇʟʟ ᴡᴏᴜʟᴅ ᴅɪᴇ ᴅᴜᴇ ᴛᴏ ᴛʜᴇ ᴅɪsᴀᴘᴘᴇᴀʀᴀɴᴄᴇ ᴏғ ᴛʜᴇ ᴘʀᴏᴛᴏᴘʟᴀsᴍɪᴄ ᴍᴀᴛᴇʀɪᴀʟ. ɪᴛ ᴀʟʟᴏᴡs ʜʏᴅʀᴏᴘʜᴏʙɪᴄ ᴍᴏʟᴇᴄᴜʟᴇs ᴀɴᴅ sᴍᴀʟʟ ᴘᴏʟᴀʀ ᴍᴏʟᴇᴄᴜʟᴇs ᴅɪғғᴜsᴇ ᴛʜʀᴏᴜɢʜ ᴛʜᴇ ʟɪᴘɪᴅ ʟᴀʏᴇʀ, ʙᴜᴛ ᴅᴏᴇs ɴᴏᴛ ᴀʟʟᴏᴡ ɪᴏɴs ᴀɴᴅ ʟᴀʀɢᴇ ᴘᴏʟᴀʀ ᴍᴏʟᴇᴄᴜʟᴇs ᴄᴀɴɴᴏᴛ ᴅɪғғᴜsᴇ ᴛʜʀᴏᴜɢʜ ᴛʜᴇ ᴍᴇᴍʙʀᴀɴᴇ.