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The cell membrane is mostly composed of phospholipid molecules. Each of these has a polar head and a non-polar tail part. The polar bits are attracted to water (hydrophilic) , and the non-polar parts repel water (hydrophobic).
In the membrane, they form a double layer - like a sandwich - the polar heads stick out, and the tails form the middle, like the filling inside the sandwich. This way, the inner and the outer surfaces of the membrane are hydrophilic, being on "good terms" with the water in the outer environment and the water in the cytoplasm.
At the same time, the membrane separates these two aqueous environments from each other - exactly because there is a non-polar middle layer, that does not allow polar substances to cross to the other side.
Wiki User
∙ 11y ago
Wiki User
∙ 13y agoMembranes are made from a phospholipid bilayer, which have a hydrophillic (polar) head and a hydrophobic (non-polar) tail. Hydrophillic molecules have an affintiy with water and thus will preffer to be in contact with water molecules or other polar mediums. In contrast the hydrophobic tail region is "water hating" and preffers to be on the interior of the cell membrane.
Phospholipids will form this continuos bilayer also called a fluid mosaic.
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Name the eight parts of a cell?
cell membrane cell wall vacoules nucleus chloroplast cytoplasm nuclear membrane Golgi body and sperm semn
Describe how the diffusion of ions across a cell membrane differs from the diffusion of nonpolar molecules across the cell membrane?
Ions need to be facilitated through a cell membrane because they are passing through a phospholipid bilayer with a hydrophobic interior. Non polar molecules are also hydrophobic, so they can pass through the membrane easily if they are small enough. Ions are polar, so they have a hard time passing through membranes.
Why do Ions and polar molecules require transport proteins to enter or leave a cell?
Not necessarily. It helps to be polar because the lipid bilayer is polar and it helps to pull molecules through, but if its a molecule that the cell doesn't want it wont pull it through. Water (a polar molecule) can go through the membrane anywhere but other nutrients need the help of transport proteins.
Despite differences in the size and shape all cells have cytoplasm and a?
cell membrane!!! not ribosomes! -wrong plant cells have cell walls and animal cells have cell membrane, it might seem right but it is wrong. Nearly all cells have a mitochondrion.^ While the answer above is correct, the real answer is Cell Membrane. So all cells have cytoplasm, AND cell membranes.
What do viruses need to carry on?
Viruses need a host cell to be able to multiply. Once they get attached to the cell membrane or cell wall of a living cell, they can take it over and "make" the living cell produce virus particles instead of cell parts. These particles can assemble into more viruses and then they break out of the cell (killing it) and begin the process again. They cannot make more viruses on their own.
Name the eight parts of a cell?
cell membrane cell wall vacoules nucleus chloroplast cytoplasm nuclear membrane Golgi body and sperm semn
What large molecules need help getting across cell membrane?
In general, molecules that cannot diffuse across the cell membrane are either very large, such as starches and fats, or very polar.
Describe how the diffusion of ions across a cell membrane differs from the diffusion of nonpolar molecules across the cell membrane?
Ions need to be facilitated through a cell membrane because they are passing through a phospholipid bilayer with a hydrophobic interior. Non polar molecules are also hydrophobic, so they can pass through the membrane easily if they are small enough. Ions are polar, so they have a hard time passing through membranes.
Does plant cells need a cell membrane?
Yes plant cells need a cell membrane. In addition to the cell membrane they also have a cell wall. Animal cells however do not have a cell wall but merely a membrane. A cell is not able to live without a membrane as it holds the organelles and cytoplasm in place.
What is the purpose of the cell membrane.?
The cell membrane regulates the passage of chemicals in or out of the cell. It is made up of a phospholipid Bi-layer consisting of many lipids much like the ones found in a detergent (Hydrophillic heads and hydrophobic tails). The tails avoid water and stay together - this makes a water proof barrier. A cell membrane is known as partially permeable as it allows non-polar molecules (or very small polar molecules such as CO2) to pass through but stops larger polar molecules, H2O for example, from passing, this is useful as it prevents excessive water loss from the cell. The cell membrane is more detailed but for your question there is no need for that.
Why do you need cholesterol in the cell membrane?
It prevents the lipids on the cell membrane from sticking together
Why does the cell need a cell membrane?
because they need to keep them self save
Does a cell wall need a cell membrane?
Of course yes
How might a polar medicine behave differently within your body than a nonpolar medicine would?
The compounds in medicine should be non polar. It is important for any drug to be able to dissolve itself through the cell membrane which consists of a lipid bi-layer, in order to diffuse in the body and circulate biologically, performing its function. Non polar compounds are lipid soluble and therefore can dissolve in the lipid layers. Polar compounds are water soluble and fail to cross the cell membrane. Therefore scientists need to be sure of using compounds that are non polar in nature so they pass through the cell membrane and enter into the blood circulation of the body and perform its due function.
What Particular molecules or ions freely cross the plasma membrane with assistance?
large polar molecules cannot pass through the membrane. only nonpolar and small polar molecules can pass through, and they only go from high to low concentration or else they need assistance from active transport.
What do animals have that replaces a cell wall?
A cell membrane. They don't need a cell wall.
Why do Ions and polar molecules require transport proteins to enter or leave a cell?
Not necessarily. It helps to be polar because the lipid bilayer is polar and it helps to pull molecules through, but if its a molecule that the cell doesn't want it wont pull it through. Water (a polar molecule) can go through the membrane anywhere but other nutrients need the help of transport proteins.
