Does the phospholipid bilayer of the cell membrane, make the membrane "water resistant," due to inward hydrophobic tails and the outward hydrophilic heads?

Yes, it does, even though water can still get through the bilayer into the cytoplasm via the integral proteins in the bilayer

How can water pass through the phospholipid bilayer if it has aquaphobic tails? Won't the water molecules get repelled out?

Aquaporins, a kind of integral, transmembrane channel protein, also help to transport water in and out of the cell.

why is a cell membrane semipermeable?

The cell is kinda like an exclusive concert. It can't let just anyone in. There are all sorts of free radicals and harmful metals that could invade the cell, not to mention those bacteria and viruses that constantly try to attack the cell. The cell needs a membrane to protect itself - to some degree - and establish an environment where it can do its job. You wouldn't want some stranger to randomly pop into your house, and neither does the cell. It does need some things from the outside world, though. That is why it allows certain particles to pass through the membrane. Hope this helps!

What is the big difference between plasma membrane and cell membrane.

there is no big difference, it is the same thing. another name for a plasma membrane (or a cell membrane) is a fluid mosiac model. again there is no big difference between these names, they are the same thing.

how many cells in my body

It's an estimated answer, but scientists predict around 37.2 trillion cells.

Main content

Course: Biology library > Unit 11

Lesson 1: Cell membranes

The cell membrane review

Google Classroom

Key terms

Term	Meaning
Cell membrane	Specialized structure that surrounds the cell and its internal environment; controls movement of substances into/out of cell
Hydrophobic	Molecule that repels water (“water-fearing”)
Hydrophilic	Molecule that is attracted to water (“water-loving”)
Amphipathic	Molecule that contains both a hydrophobic and a hydrophilic end
Phospholipid	Amphipathic lipid made of glycerol, two fatty acid tails, and a phosphate group
Phospholipid bilayer	A biological membrane involving two layers of phospholipids with their tails pointing inward
Semipermeable membrane	Membrane that allows certain substances to pass through

Structure and function of the cell membrane

The cell membrane is semipermeable (or selectively permeable). It is made of a phospholipid bilayer, along with other various lipids, proteins, and carbohydrates.

Each phospholipid is amphipathic, with two hydrophobic tails and a hydrophilic head. The hydrophobic tails face inward towards one another, and the hydrophilic heads face outwards.

The unique structure of the cell membrane allows small substances (like oxygen or carbon dioxide) to easily pass through.

Common mistakes and misconceptions

Hydrophobic tails face inward and hydrophilic heads face outward. If you get these two ends mixed up, think of the root word “phobia” which means “fear.” Hydrophobic tails fear the water, so they will always try to be as far as possible from the water solutions in and out of the cell.
The cell membrane contains a phospholipid bilayer, but the terms are not interchangeable. Part of the cell membrane is a phospholipid bilayer, made of two layers of phospholipid molecules. However, the cell membrane also contains other macromolecules like membrane proteins, and carbohydrates. Therefore, we can say that the cell membrane is made of a phospholipid bilayer, but it is not only made of it.

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Ishaan D
Posted 6 years ago. Direct link to Ishaan D's post “Does the phospholipid bil...”
Does the phospholipid bilayer of the cell membrane, make the membrane "water resistant," due to inward hydrophobic tails and the outward hydrophilic heads?
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(9 votes)
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- Kofi A.
  Posted 6 years ago. Direct link to Kofi A.'s post “Yes, it does, even thoug...”
  Yes, it does, even though water can still get through the bilayer into the cytoplasm via the integral proteins in the bilayer
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nv147401
Posted 5 years ago. Direct link to nv147401's post “why is a cell membrane se...”
why is a cell membrane semipermeable?
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(3 votes)
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- elijahsmart708
  Posted 5 years ago. Direct link to elijahsmart708's post “The cell is kinda like an...”
  The cell is kinda like an exclusive concert. It can't let just anyone in. There are all sorts of free radicals and harmful metals that could invade the cell, not to mention those bacteria and viruses that constantly try to attack the cell. The cell needs a membrane to protect itself - to some degree - and establish an environment where it can do its job. You wouldn't want some stranger to randomly pop into your house, and neither does the cell. It does need some things from the outside world, though. That is why it allows certain particles to pass through the membrane. Hope this helps!
  Comment on elijahsmart708's post “The cell is kinda like an...”
  (36 votes)
ChiknWings
Posted 9 months ago. Direct link to ChiknWings's post “Do u like whoppers? How m...”
Do u like whoppers? How many cells are in one?
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(8 votes)
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- Somebody.
  Posted 8 months ago. Direct link to Somebody.'s post “More than 1.”
  More than 1.
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  (8 votes)
KyzarO
Posted 8 months ago. Direct link to KyzarO's post “how many cells in my body”
how many cells in my body
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- Bani Hundal
  Posted 8 months ago. Direct link to Bani Hundal's post “About 37 trillion cells”
  About 37 trillion cells
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JoyceIsBreathing ジョイス
Posted 6 years ago. Direct link to JoyceIsBreathing ジョイス's post “How can water pass throug...”
How can water pass through the phospholipid bilayer if it has aquaphobic tails? Won't the water molecules get repelled out?
Button navigates to signup pageComment on JoyceIsBreathing ジョイス's post “How can water pass throug...”
(5 votes)
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- Jaden Ong
  Posted 4 years ago. Direct link to Jaden Ong's post “Aquaporins, a kind of int...”
  Aquaporins, a kind of integral, transmembrane channel protein, also help to transport water in and out of the cell.
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  (5 votes)
salma
Posted 2 years ago. Direct link to salma's post “i have a question i do no...”
i have a question i do not understand the word phobia can anyone comment to explain a bit more thanks.
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(4 votes)
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- Aubrey Cofer
  Posted a year ago. Direct link to Aubrey Cofer's post “phobia is greek for fear ...”
  phobia is greek for fear >
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pbillingsley27
Posted 7 months ago. Direct link to pbillingsley27's post “How many cells are there ...”
How many cells are there in a small dog
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(4 votes)
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- maeshev
  Posted 7 months ago. Direct link to maeshev's post “A lot”
  A lot
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MadalynG
Posted 2 years ago. Direct link to MadalynG's post “What is the big differenc...”
What is the big difference between plasma membrane and cell membrane.
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(3 votes)
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- timmy_trumpet_2008
  Posted 2 years ago. Direct link to timmy_trumpet_2008's post “there is no big differenc...”
  there is no big difference, it is the same thing. another name for a plasma membrane (or a cell membrane) is a fluid mosiac model. again there is no big difference between these names, they are the same thing.
  Comment on timmy_trumpet_2008's post “there is no big differenc...”
  (5 votes)
Sonic D. Hedgehog
Posted 5 months ago. Direct link to Sonic D. Hedgehog's post “Hiya! What if a cell has ...”
Hiya!
What if a cell has no cell membrane?
Thanks!
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(3 votes)
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- 28fange
  Posted 4 months ago. Direct link to 28fange's post “Short answer: It dies.”
  Short answer: It dies.
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hewett addy
Posted 8 months ago. Direct link to hewett addy's post “how many cells in my bod...”
how many cells in my body
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- IVY PARK
  Posted 8 months ago. Direct link to IVY PARK's post “It's an estimated answer,...”
  It's an estimated answer, but scientists predict around 37.2 trillion cells.
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  (6 votes)