Permeability of Cell Membrane

[@saraibr850]

I love how greatly explained and how neat the lectures are, but a note, water molecules pass through the membranes so quickly due to Aquaporins. These have restrictions as to how water molecules can pass in an out of them, but they are solely responsible to the fast interaction

[@AKLECTURES]

+sara ibr I do a separate lecture on aquaporins, you can learn more about them there.

[@saraibr850]

+AK LECTURES (Andrey K) oh, ok.. thats awesome.. thank you

[@edoardobragadin779]

I have never listen to anyone that explains better than you, everything makes sense, unbelievable

[@frankaddeo6132]

I still don't know how this gent's videos get such low hits. Thank you for your contributions to education!

[@Ultearss]

Uhhhh thank you!! I got a dare from my AP bio teacher to explain why water can go through the bilayer. I hope this will answer the question tmw!

[@hennaandmorebyifrah4892]

You made it so easy for me!! Thnku so much

[@dewanchettri2580]

Great sir . From india .

[@KulturaTV]

Why does the small non-polar molecule not get repelled by the polar hydrophilic heads of the phospholipids? Surely if polar molecules can't diffuse across the membrane due to the hydrophobic core, non-polar molecules shouldn't be able to either? In fact, why can any transport at all happen across the membrane, if all molecules are either polar or non-polar (ignoring transport through channel/carrier proteins and aquaporins)?

[@beautyqueen5002]

First there are induced dipole-dipole interactions between polar and non-polar molecules. The same interactions are formed here. Second molecules are not simply polar and non-polar, we need to consider the concentration gradient and electrochemical gradient here. So, transport is actually function of a membrane but proteins channels and carriers just help increase its selective permeability allowing more molecules to effectively pass through

[@helenasalgadobotero3050]

Demaaasiado demasiado bueno!!!! thanks, you saved my semester

[@nooruleman9530]

I don't know if my concept is wrong or what. I cannot understand one thing. I hope anybody can help me understand. Small non-polar molecules have to pass through hydrophilic(polar) heads, but they are non-polar, so how can they pass through a polar region?

[@beautyqueen5002]

Inducing a dipole moment in a non-polar molecule as it passes through a cell membrane involves changes in the distribution of electrons within the molecule. This phenomenon can occur during the process of facilitated diffusion or passive transport, where molecules move across the cell membrane without the expenditure of energy (as opposed to active transport, which requires energy). Here's a simplified explanation of how this can happen: Non-Polar Molecule: Let's start with a non-polar molecule, which typically has an equal distribution of electrons and no permanent dipole moment. This means the molecule is electrically neutral. Electric Field in the Membrane: The cell membrane has an electric field due to the presence of various charged ions and molecules on both sides of the membrane. This electric field can interact with the non-polar molecule as it approaches the membrane. Induced Dipole Moment: When the non-polar molecule approaches the cell membrane, the electric field within the membrane exerts a force on the electrons within the molecule. This force causes the electrons to temporarily redistribute within the molecule, creating an induced dipole moment. Alignment with the Field: The electrons tend to shift slightly away from the side of the molecule facing the positively charged part of the electric field and slightly toward the side facing the negatively charged part of the field. This redistribution of electrons creates a partial positive charge on one end of the molecule and a partial negative charge on the other end. Interaction with the Membrane: Now that the molecule has a dipole moment, it can interact more readily with the charged or polar regions of the cell membrane. This interaction facilitates the passage of the molecule through the membrane because the partial charges on the molecule can interact with polar or charged regions of the lipid bilayer or membrane proteins. Passage Through the Membrane: As the molecule moves through the membrane, it may continue to experience changes in its electron distribution and dipole moment as it interacts with the varying electric field. However, once it has crossed the membrane and is in the new cellular environment, the molecule may return to its non-polar state. It's important to note that this description simplifies the complex interactions that occur during molecular transport across the cell membrane. In reality, the process involves many factors, including the specific properties of the membrane, the nature of the molecule, and the surrounding environment. Nevertheless, induced dipoles play a significant role in facilitating the transport of non-polar molecules through cell membranes, particularly in processes like passive diffusion.

[@sohaya583]

You are awesome

[@quratulan133]

Hi sohaya On notes it is written that charged or polar molecule don't readily pass across the membrane bcoz sch molecule lose the stronge interaction with water Bt as we know polar molecules form have strong interaction with water Is it correct written there??

[@sohaya583]

@Qurat It is that charged and polar molecules don't readily pass because they have binding with water and almost no binding with lipid tail within membrane and thus can't pass through its difficult for them to break interaction with water and pass through hydrophobic lipid tail

[@sohaya583]

@@quratulan133 hope you got it

[@quratulan133]

@@sohaya583 yeas I got it thanku 🥰😍❤

[@sohaya583]

@@quratulan133 my pleasure ☺️

[@defirush672]

What happens to the membrane potential if you increase sodium permeability?

[@zaina8776]

Thank you!

[@milesholmes9509]

GREAT lecture!

[@AKLECTURES]

Miles Holmes Thanks again :)

[@mariahslittlelamb8049]

@@AKLECTURES Love you

[@jescankya878]

great sir

[@ridanikhan2901]

I have a question, as we know plasma membrane is highly selective membrane. how come heavy metals pass through it?

[@beautyqueen5002]

With the help of special ion channels ( transport proteins) or ionophores (carrier proteins)

[@beautyqueen5002]

With the help of special ion channels ( transport proteins) or ionophores (carrier proteins)

[@li-lianang8304]

I dont really understand how because water doesnt have a full charge, it passes through the membrane more easily. Could you help to explain?

[@nooruleman9530]

Water molecules are relatively small and the individual molecules have partial positive and partial negative charges. when they pass through the hydrophobic tails there are no charge interactions due to the relatively small charge and as they are small they can easily. navigate through the hydrophobic tails.

[@nooruleman9530]

This phenomenon is simple diffusion. Otherwise membranes have special channels for water molecules where they pass through facilitated diffusion. These are called aquaporins. Nephrons of Kidney are rich in aquaporins

[@bennettchick]

Who gave this a thumbs down?