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Why are the tails in a cell membrane pointed towards the middle bilayer?
Wiki User
∙ 11y ago
What you are referring to is the lipid bilayer, which is basically the cell membrane. Animal cells have this so that they can control what enters and leaves the cell. (This is called being selectively permeable) This helps the animal cell maintain homeostasis, which is controlling your insides despite outside conditions.
Wiki User
∙ 12y ago
Wiki User
∙ 8y agoThe bilayer forms naturally when the component molecules are immersed in water. With one end hating water and the other loving it, the only stable arrangement is for the water hating ends to face each other and the water loving ends to stick out into the water.
Wiki User
∙ 11y agolipids
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How does the structure of the plasma membrane allow materials to move across it in both directions?
The structure of the plasma membrane consists of the phospholipid bilayer, which gives it a fluid structure, and not rigid, allowing the materials ease to pass through. Next, there are also integral proteins which can be thought of as 'tunnels', allowing the materials to come in and out. Then, there are peripheral proteins which also aid in getting the materials inside an out. On the cell membrane, there are receptors which recognize outside materials, and if they are really big, the cell engulfs these molecules through endocytosis [pinocytosis, and phagocytosis, which are basically for liquid molecules, and solid molecules]. This takes us back to the fluidity of the cell membrane. That's roughly how the cell membrane allows for the entering and exiting materials.
When phospholipid molecules are placed in water they form bilayer membranes Describe what you think happens to cause the formation of the bilayer membranes?
The hydrophobic and hydrophilic effect. The nonpolar tails join together in the middle of the bilayer away from water and the polar heads that can tolerate water are on the outside of the bilayer.
Can polar molecules and molecules that have chargers sneak through the nonpolar middle portion of the phospholipid bilayer?
No, they are not. Micelles are formed by amphipathic molecules, that is molecules having both poplar and nonpolar regions, such as phospholipids or fatty acids. The polar region stays to the outside of the sphere as it can interact with water or some other polar solvent and the nonpolar regions are forced to the center.
What gives the plasma membrane the ability to self-reassemble?
Hydrophilic end
Why does a cell membrane need polar and non polar parts?
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.
When a membrane is freeze fractured the bilayer splits down the middle between the two layers of phospholipids In the electron micrograph of a freeze-fractured membrane the bumps seen on the fracture?
Integral Proteins.
Why would a substance not be able to pass through a membrane by diffusion?
Water cannot diffuse a plasma membrane because of the fact that the phosphate heads of the phospholipids are hydrophilic, the hydrocarbon tails of the phospholipids are hydrophobic, meaning they repel water. The bilayer phospholipid model of the plasma membrane shows that the phophates face outward on either side of the membrane and the lipid tails are in the middle of the bilayer.
What kind of lipids make up the bilayer that forms the cell membrane?
Phospholipids
Why are fat soluble molecules the only molecules that permeate across a cell membrane?
Because small non polar molecules are the ones able to cross due to the fact that the membrane consists of a phospholipid bilayer where the middle is composed on non polar tails
How does the structure of the plasma membrane allow materials to move across it in both directions?
The structure of the plasma membrane consists of the phospholipid bilayer, which gives it a fluid structure, and not rigid, allowing the materials ease to pass through. Next, there are also integral proteins which can be thought of as 'tunnels', allowing the materials to come in and out. Then, there are peripheral proteins which also aid in getting the materials inside an out. On the cell membrane, there are receptors which recognize outside materials, and if they are really big, the cell engulfs these molecules through endocytosis [pinocytosis, and phagocytosis, which are basically for liquid molecules, and solid molecules]. This takes us back to the fluidity of the cell membrane. That's roughly how the cell membrane allows for the entering and exiting materials.
What is the composition of plasma membrane?
there are four main parts of the plasma membrane of a cell. 1) the lipid bilayer: this is made up of amphipathic molecules, with the polar heads on the outsides and the non polar tails in the middle. this part is semi-permeable. 2) the proteins: these work as canals to pump larger molecules through the bilayer which couldn't otherwise fit. 3) the carbohydrates: these are different on each cell and are used as the "chemical id tag" for identifying other cells. 4) the cholesterol: this is used to keep the lipid bilayer as plasma instead of turning into a solid. hope this helps (:
How do water soluble molecules enter or exit a cell?
Water molecules move by osmosis through the cell membrane which is a selectively permeable membrane. Since the middle of the lipid bilayer is hydrophobic, the movement of water is made possible by water channels or aquaporins in the membrane.
When phospholipid molecules are placed in water they form bilayer membranes Describe what you think happens to cause the formation of the bilayer membranes?
The hydrophobic and hydrophilic effect. The nonpolar tails join together in the middle of the bilayer away from water and the polar heads that can tolerate water are on the outside of the bilayer.
How does the cell membrane acts as the gatekeeper for the cell?
The cell membrane (also called the plasma membrane or plasmalemma) is the biological membrane separating the interior of a cell from the outside environment.
How are proteins positioned within the membrane?
The protein is anchored into the membrane by its nonpolar region, but the protein remains moblie. To explain it more, the middle section of the protein is made of many nonpolar amino acids. This nonpolar coil fits into the nonpolar interior of the lipid bilayer allowing the protein to float in the membrane.
What is the dividing line between the middle ear and the external ear?
The tympanic membrane separates the external ear from the middle ear.
Why don't ions pass through cell membran?
Only small and uncharged particles can pass through the nonpolar part of the membrane interior. Ions are charged and won't pass through a membrane by passive diffusion. Certain ions do pass through membranes by other mechanisms, though.
