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Resumen para examen de biologa cell membrane

Temas:

Cell membrane structure Passive Transport Active Transport

Cell membrane Structure:

The cell membrane is built up of phospholipids, which are two things together; the head and

the tail. The head is hydrophilic and the tail is hydrophobic, that they do resist water and that

they do not resist water respectively. Because of that the tails go inside the cell or intracellular

and the head goes extracellular or outside. The heads are called phosphates and the tails are

called lipids. See this diagram to understand:

Phosphates

Lipids

Lipids

Phosphates

This way, the heads clos the entrance for water because the tails cant resist the water, and so

on, that is the border of the cell, the cell membrane, in between the layers of phospholipids,

are the rest of organelles.

Passive transport:

In general, passive transport is the transport from the inside to outside of the cell or vice-

versa, it works without energy also known as ATP, and it always goes from the side with a

higher concentration of those molecules to the side with a lower concentration of those

molecules. There are three kinds of passive transport: Diffusion, Osmosis and Facilitated

diffusion.

Diffusion:

The movement of small particles from an area of high concentration to an area of low

concentration, through a semi permeable membrane (accepts some liquids)

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Osmosis:

The transport of water molecules through a permeable membrane, again form a high

concentration to a low concentration of water molecules. There are three types of osmosis:

Hypotonic, hypertonic and isotonic. Hypotonic means that there are fewer molecules inside

the cell than outside, hypertonic means that there are more molecules of water inside the cell

than outside. Isotonic means that there is the same amount of water molecules in both sidesof the cells.

Facilitated diffusion:

Movement of large particles through a channel protein; moves with the help of the proteins.

Active Transport:

The movement of particles against the normal way, it goes from a low concentration of

particles to a high concentration of particles and it does require atp: energy. There are also

three kinds of active transport; endocytosis, exocytosis and sodium-potassium pump.

Endocytosis:

Process in which the cell absorbs a molecule,

Exocytosis:

Process in which the cell directs molecules out of the cell

This is exocytosis but endocytosis is just

the other way around.

Sodium-Potassium pump:

System that works to give sodium or potassium to the other side of the cell, it always works by

passing 3 sodium particles and then 2 potassium particles. It also requires energy to work

which is given when the particles are going to pass through

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