What creates selective permeablility of plasma membrane?

Question

I am working on a packet and that is one of the questions. I have tried to research the answer but i cannot seem to find a straightforward answer. If someone could please help me out, I would greatly appreciate it. Thanks!

Answer 1

this would be easier to google if you spelled it correctly, i imagine.

lets assume you arent asking: what 'makes' it selectively permeable, but what 'causes' selective permeability.

the easy answer would be the code of the construction of the membrane (what makes me a boy--my code--genetics, what makes my air filter let air pass but not dog hair--the code--the engineering diagram) which usually defines permeability in one of three ways: rate, shape or size.
rate: how fast can water go through my reverse osmosis (LOL) filter. 50 gallons a day. but ALL h20 goes through.
shape: what can get through the cell membrane, anything that matches the shape of the protein that carries it across.
size: large rocks get caught on the screen, but small rocks go through.

maybe you can define a little...clarify seletively permeable or selective permeability, human biology or water filtration?

either way, this link might help (or might be 5 years behind you! sorry, dont know!)

Answer 2

Hi Chad. The plasma membrane is a lipid bilayer. In the world of chemistry (that includes biochemistry) "like dissolves like". So the lipid plasma membrane is permeable to other lipids but not to polar molecules (e.g. water). Polar molecules and atoms (e.g. magnesium or potassium) can only pass through the plasma membrane into the cell via specialized channels or pores. These channels and pores are made up of proteins embedded in the plasma membrane. Large molecules like glucose (which is also polar and therefore cannot pass through the membrane) are absorbed into the cell by endocytosis.

Many large molecules that are lipids and, therefore, non-polar, such as testosterone, estrogen, vitamin A, etc. can enter the cell easily because the plasma membrane is permeable to these and other lipids.

Hope this is helpful. Best wishes and good luck.

Answer 3

The plasma membrane is made of a lipid bilayer made of molecules with a phosphate head and fatty acid chains. The phosphate heads create the boundary while the fatty acid chains are on the inside. Since the chains are nonpolar, only nonpolar molecules can pass through. The selective permeability is also affected by factors such as the size of the molecule, if it is too large it probably won't be able to pass through the plasma membrane.
Hope this helped!

Answer 4

The plasma membrane is polar, meaning that water can easily pass through it. Also, it is flexible, which allows for movement. The cell is selectively permeable for the purpose of maintaining homeostasis. In this way, the cell gets rid of wastes and takes in nutrients and water that it needs.

However, the basic answer you're looking for is that the plasma membrane is polar and flexible, as I stated previously. Good luck! =D

Answer 5

Try research on the lipid bilayer and transport proteins. If you need to know about passive or active transport maybe this will help. Passive transport: No energy required (no ATP), requires diffusion, and diffusion continues until equalibrium is reached.
Active transport: Requires energy (ATP) expended by the cell itself, moves molecules against or across concentration gradient. If you need more specifics just research active and passive transport. Theres not much detail, but maybe it will help.

Answer 6

Proteins, proteins, proteins. Proteins allow some molecules to pass while other don't. That's how the cell controls glucose, action potentials, metabolism, defense, and thousands of other functions of the body