Do phospholipid bilayers ONLY form in water?

Tj789

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kinda confused...

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Scienceteacher

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Can you explain what you're confused by?

Phospholipid bilayers do form in water and since cells are essentially little bags of water (with dissolved chemicals etc), phospholipid bilayers form the cell membrane and also membranes of organelles such as mitochondria.

What else were you thinking? Ethanol? Or another type of solvent?

I have a degree and PhD in Biochemistry so I can probably help you.

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Tj789

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(Original post by Scienceteacher)
Can you explain what you're confused by?

Phospholipid bilayers do form in water and since cells are essentially little bags of water (with dissolved chemicals etc), phospholipid bilayers form the cell membrane and also membranes of organelles such as mitochondria.

What else were you thinking? Ethanol? Or another type of solvent?

I have a degree and PhD in Biochemistry so I can probably help you.

I suppose im confused because I dont know if cell membranes are ALWAYS surrounded by water. And when looking at the fluid mosaic model clearly the people who came up with it think that the bilayer is always present, and that means that they are suggesting the cell membrane is always surrounded by water???

Tanx

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Scienceteacher

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Yes effectively the cell membrane is always surrounded by water. Cells do touch and they do contain loads of dissolves chemicals etc but it's not wrong to assume that they are always surrounded by water.

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Tj789

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(Original post by Scienceteacher)
Yes effectively the cell membrane is always surrounded by water. Cells do touch and they do contain loads of dissolves chemicals etc but it's not wrong to assume that they are always surrounded by water.

Ok tanx!!

Oh just a quick question: could u give me a definition of passive transport? Because in my book it says its transport which only uses kinetic energy and it says diffusion is passive but then it says diffusion doesnt use any energy?

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borysek01

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(Original post by Tj789)
Ok tanx!!

Oh just a quick question: could u give me a definition of passive transport? Because in my book it says its transport which only uses kinetic energy and it says diffusion is passive but then it says diffusion doesnt use any energy?

Definitions are different from book to book, exam board to exam board.

There are two forms of transport - active and passive. Active transport is when a form of energy is required for substances to move through (the membrane in this case). For example, active uptake is a form of active transport. It requires ATP (a chemical) for it to happen.

Then there's passive transport. Passive, like the name suggests, does not require any energy. Simple diffusion (or just diffusion, sometimes it's called) is a form of passive transport. It happens because there's a concentration gradient (more molecules on the outside than on the inside cause them to diffuse in until they become equal). It does not require ATP, but it uses its own kinetic energy (moving energy) to pass through.

Hopefully that helps.

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SuperiorGenius

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(Original post by Tj789)
Ok tanx!!

Oh just a quick question: could u give me a definition of passive transport? Because in my book it says its transport which only uses kinetic energy and it says diffusion is passive but then it says diffusion doesnt use any energy?

By kinetic energy it means the natural movement of the particles. So it's not using any energy because it doesn't have to create it's own. There are two types of passive transport - facilitated diffusion and diffusion (I'm assuming you do AS biology) and neither of them require energy in the form of ATP.

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Tj789

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(Original post by SuperiorGenius)
By kinetic energy it means the natural movement of the particles. So it's not using any energy because it doesn't have to create it's own. There are two types of passive transport - facilitated diffusion and diffusion (I'm assuming you do AS biology) and neither of them require energy in the form of ATP.

I think that clears it up. I was kind of confused because my OCR AS Bio book said passive transport relies only on kinetic energy but then I thought Id be contradicting myself if I said "passive transport is a form of transport that doesnt require any energy, but it only relies on kinetic energy" but I guess if its the natural movement of molecules then it makes sense

Tanx

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Tj789

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(Original post by borysek01)
Definitions are different from book to book, exam board to exam board.

There are two forms of transport - active and passive. Active transport is when a form of energy is required for substances to move through (the membrane in this case). For example, active uptake is a form of active transport. It requires ATP (a chemical) for it to happen.

Then there's passive transport. Passive, like the name suggests, does not require any energy. Simple diffusion (or just diffusion, sometimes it's called) is a form of passive transport. It happens because there's a concentration gradient (more molecules on the outside than on the inside cause them to diffuse in until they become equal). It does not require ATP, but it uses its own kinetic energy (moving energy) to pass through.

Hopefully that helps.

But wont I be contradicting myself saying passive transport requires no energy, but then say requires kinetic?

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SuperiorGenius

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(Original post by Tj789)
I think that clears it up. I was kind of confused because my OCR AS Bio book said passive transport relies only on kinetic energy but then I thought Id be contradicting myself if I said "passive transport is a form of transport that doesnt require any energy, but it only relies on kinetic energy" but I guess if its the natural movement of molecules then it makes sense

Tanx

No problem

Anymore questions about AS biology then hit me up.

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borysek01

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(Original post by Tj789)
But wont I be contradicting myself saying passive transport requires no energy, but then say requires kinetic?

What is meant by passive transport - is that it requires no external energy. It's just naturally assumed that each particle that moves has kinetic energy. If they had no kinetic energy, they could not move through the membrane as they would be stationary.

Passive and active refers to external sources of energy that supply the movement.

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Tj789

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(Original post by SuperiorGenius)
No problem

Anymore questions about AS biology then hit me up.

Haha then I'd be hitting you loads!

I think I got it so basically is this right: Passive transport is a type of transport which requires no cellular energy just the natural kinetic energy of molecules? Because this is probably a really stupid question but you know process like active transport which do require energy it gets that energy from the cell right not the molecules?

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Tj789

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(Original post by borysek01)
What is meant by passive transport - is that it requires no external energy. It's just naturally assumed that each particle that moves has kinetic energy. If they had no kinetic energy, they could not move through the membrane as they would be stationary.

Passive and active refers to external sources of energy that supply the movement.

I just made a comment just previous to another guy give my understanding of it now- can you see if ive got it right please

Tanx!!

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SuperiorGenius

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(Original post by Tj789)
Haha then I'd be hitting you loads!

I think I got it so basically is this right: Passive transport is a type of transport which requires no cellular energy just the natural kinetic energy of molecules? Because this is probably a really stupid question but you know process like active transport which do require energy it gets that energy from the cell right not the molecules?

That's right but you could phrase it better. Say that Active transport requires energy in the form of ATP and passive transport doesn't require energy but uses the natural movement of particles.

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Tj789

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(Original post by SuperiorGenius)
That's right but you could phrase it better. Say that Active transport requires energy in the form of ATP and passive transport doesn't require energy but uses the natural movement of particles.

Ok tanx so much!

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borysek01

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(Original post by Tj789)
Ok tanx so much!

At AS level, passive and active only refers to ATP. Easiest way to understand (and say it, because the mark scheme will accept it) is that passive does not require ATP and active does.

You will later on (if you haven't already) learn what ATP is and where it's made (mitochondria, to be precise).

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borysek01

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(Original post by Tj789)
Haha then I'd be hitting you loads!

I think I got it so basically is this right: Passive transport is a type of transport which requires no cellular energy just the natural kinetic energy of molecules? Because this is probably a really stupid question but you know process like active transport which do require energy it gets that energy from the cell right not the molecules?

That is not correct. Celluar is not the word to use. See SuperiorGenius' answer to see how to phrase it.

(Original post by SuperiorGenius)
Active transport requires energy in the form of ATP and passive transport doesn't require energy but uses the natural movement of particles.

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Tj789

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(Original post by borysek01)
That is not correct. Celluar is not the word to use. See SuperiorGenius' answer to see how to phrase it.

in my book it says "without using energy from the cell" ergo without using "cellular energy"....

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