LeoNicole
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Hey,

So we were going through this powerpoint about the cell membranes and the phosphlipids etc. and I have a few questions that my teacher couldn't really answer:

1) I didn't really get the whole polarity, like why does it matter at all in the arrangement of the phospholipds?
2) Why do non-polar molecules such as oxygen pass through membranes more easily that polar molecules such as water?
3) Does is matter what kind of cholesterol is in the membrane? LDL/HDL? If so, how does it matter and what is the overall difference between LDLs and HDLs?

Thaaaanks in advance, I know these questions may seem stupid but sometimes I just can't understand little details

xx
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tim3
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(Original post by LeoNicole)
Hey,

So we were going through this powerpoint about the cell membranes and the phosphlipids etc. and I have a few questions that my teacher couldn't really answer:

1) I didn't really get the whole polarity, like why does it matter at all in the arrangement of the phospholipds?
2) Why do non-polar molecules such as oxygen pass through membranes more easily that polar molecules such as water?
3) Does is matter what kind of cholesterol is in the membrane? LDL/HDL? If so, how does it matter and what is the overall difference between LDLs and HDLs?

Thaaaanks in advance, I know these questions may seem stupid but sometimes I just can't understand little details

xx
Hi LeoNicole!

1) Yes the polarity matter is it helps the cell membrane to form a bilayer! The non polar tails face each other( they have different types of attractive forces but they are just not attracted to water) and polar heads face the soluble environment outside.

2) Non-polar stuff allows only allows non-polar stuff to go though. Remember polarity here refers to solubility in water. Hence if anything is polar(i.e it is soluble in water)...the non-polar does not like it, Hence it does not allow to pass through it

3.) Well it kinda does. The cholesterol helps to determine the fluidity of the cell membrane. The more cholesterol there is the more fluid the membrane is.
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Blobar
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I think you need a new teacher if they couldn't answer that especially the first question.
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tim3
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And it is ok to ask as many questions as you like to clarify the concepts. As ling as it prepares you to score really high in your exams
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Joshalos
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(Original post by LeoNicole)
Hey,

So we were going through this powerpoint about the cell membranes and the phosphlipids etc. and I have a few questions that my teacher couldn't really answer:

1) I didn't really get the whole polarity, like why does it matter at all in the arrangement of the phospholipds?
2) Why do non-polar molecules such as oxygen pass through membranes more easily that polar molecules such as water?
3) Does is matter what kind of cholesterol is in the membrane? LDL/HDL? If so, how does it matter and what is the overall difference between LDLs and HDLs?

Thaaaanks in advance, I know these questions may seem stupid but sometimes I just can't understand little details

xx
There isn't a type of cholesterol in the cell membrane; cholesterol is just cholesterol. It provides stability to the cell membrane and maintains fluidity.

HDL and LDL are lipoproteins and are the body's method of transporting lipid and cholesterol around the body in the blood stream.

HDL is high density lipoprotein which means it has much more protein than cholesterol. Cholesterol in HDL is transported to the liver where it is converted to bile acids and so the cholesterol can be excreted. It is the body's only method of cholesterol excretion.

LDL is low density lipoprotein and has more cholesterol than protein. LDL can cause deposition of cholesterol in artery walls which can lead to athersclerotic plaques forming.
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