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Cell or Plasma Membranes

Every cell has a cell membrane (plasma membrane) that separates the interior of the cell from the outside environment. One of the most important functions of this biological membrane is to protect the cell from outside threats by controlling the movement of substances in and out of the cell.

1,116 Questions

What is used by ribosomes to assemble proteins?

Ribosomes are formed from the process called Protein Synthesis.

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the above is not accurate. Ribosomes also contain RNA.

The question is not phrased precisely hence we can not find out what the querent wanted to know. Previously this answer contained information that ribosomes self-assemble.

Why do cells perform endocytosis?

to move different materials in the vesicles!. (YEa its really legit i promise!:)

What are the cell organelle without a membrane in animal cell?

The cell organelles inside and animals cell membrane are the; nucleus (control center), Golgi apparatus (sends things out of cell) , ribosomes(makes proteins), endoplasmic reticuhem (transport), lysome (destroys foreign matter) and the mitochidra (power house).

What characteristic makes the cell membrane selectively permeable?

Passive and active transport. Passive transport doesn't require the cell's energy, while active transport does.

Why is there a cell necules?

The cell nucleus contains the genetic material (DNA) of the cell and acts as the control center, regulating all cellular activities such as growth, metabolism, and reproduction. It also protects the DNA from damage and regulates the flow of molecules in and out of the nucleus.

Which biomolecules make up the cell membrane?

Only the http://wiki.answers.com/Which_organelles_are_made_of_plasma_membrane#membrane is made of phosophlipids as a semipermiable membrane. No other structures are made from it.

There are, however, organelles which are surrounded by a plasma membrane. These include nucleus, http://wiki.answers.com/Which_organelles_are_made_of_plasma_membrane#, peroxisomes, lysosomes and chloroplasts (in plants).

*taken from another answer*

Read more: http://wiki.answers.com/Which_organelles_are_made_of_plasma_membrane#ixzz17ZxEF1Z3

What substances moves across the cell membrane with the help or carrier molecules?

Ions across a cell membrane. It is a form of passive transport. Ions such as sodium(Na+), potassium (K+), calcium (Ca2+), and chloride (Cl-). Each ion channel is usually specific for one type of ion.

What is meant by the statement The cell membrane is said to be fluid?

This membrane is called the fluid mosaic model as it is a mixture of phospholipids, cholesterol, proteins and carbohydrates. Most of the membrane is composed of phospholipid molecules. These allow the membrane to be rather fluid.
Embedded in this membrane are proteins which give some structure to the membrane. The 3rd components are proteins or glycolipids.
The proteins sort of float on the surface of the membrane like islands in the sea.

What is The plasma membrane helps to maintain a cells what?

The plasma membrane helps to maintain homeostassi within the cell by allowing substances to move in and out of the cell the plasma membrane is used to maintain homeostasis within the cell by allowing substances to move in and out of the cell

What effect would the concentration gradient have on the rate of water movement through cell membranes?

Concentration gradient is crucial to the structure of a cell. Cells need to be in an isotonic solution to survive *(unless they are specifically designed cells that are made to deal with being in a non-isotonic solution). Isotonic solution means that the concentration of solute outside the cell is equal to the inside of the cell.

The reason being isotonic with their environment is so important to a cell is because of the rules of osmosis. Cell membranes can pass water freely through specific channels that let it in and out. And, because of the rules of osmosis, water wants to be at equal concentration inside and out. The water will move accordingly to try and even out the concentrations of the intracellular environment and extracellular environment. To think of it in a simpler way, it does not want one side of a membrane to be salty and another side to be fresh, it will move so they are both at equal saltiness. Remember that the salt cant move across the membrane, so to even things out the WATER must move. (we are not always dealing with salt when we talk about osmosis, but to learn the principles, we can simplify it and think of solute concentrations in terms of salty or fresh water)

So, if a cell is put into HYPERtonic solution, where the concentration of solute outside the cell is much higher than that of inside the cell, it will shrivel. This is because water inside the cell rapidly leaves, to try and make the concentration of solutes inside and outside equal. You can remember this by remembering what happens if you drink salt water. You get dehydrated. Or, if you put a freshwater fish into very salty water, it will shrivel and die. This also explains why you gargle salt water when you have a sore throat- shrivel those bacteria up!

On the contrary, if you put a cell in a HYPOtonic solution, (solution where the concentration of solute is very low outside compared to the inside of the cell) the cell will blow up like a balloon. This is because water rapidly flows into the cell to try and make concentrations of solute equal inside and outside. The cells can blow up so big that they can pop, or lyse to use the proper term.

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.

Why are membrane proteins necessary for active transport?

Active transport, requires ATP to fuel it as it goes against the gradient present in cells. Substances can drift along a gradient into and out of cells, but must be pushed against a gradient.

Could a cell survive without a cell mebrane?

Quite simply, the cell would no longer be a contained 'system' and as such the content of the cell would spill into its environment.

This can be seen when a cell 'lyses' or bursts

What is the basic structure of the plasma membrane?

The framework of the cell membrane is formed by the lipid bilayer. The lipid bilayer is composed of two layers of fat cells organized in two sheets. This is what provides the barrier that makes the boundaries of the cell.

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.

What makes up part of the Cell's membranes?

The main 'component' of the Cell's membranes are fatty acids, also known as lipids.

The day the plasma membrane stopped working?

If the plasma membrane stopped working, the cell would no longer be able to regulate what substances enter and exit the cell. This would disrupt cellular functions and could ultimately lead to cell death. The plasma membrane plays a crucial role in maintaining the internal environment of the cell, so its dysfunction would have significant consequences.

Can substances move in and out of the cell membrane?

Yes, how else could the cell live. Cell membranes have structures (holes) in them to allow things to move in and out. These holes are special structures in the membrane and they "control" what goes across the membrane.

I have made a link below to a diagram of the cell membrane to show some of these structures.

Is the cell wall between the cell membrane and the nucleus?

No the cell wall is the outside layer of the cell surronding the cell membrane and nucleus.