Cell Processes: Moving In and Out of the Cell

A cell can only survive if food molecules are taken in and if waste materials are removed. Materials enter and leave the cell through the cell membrane.

Cell Membranes Permeable Membrane Impermeable Membrane allows all substances to pass through Impermeable Membrane does NOT allow substances to pass through Most cell membranes allow only certain substances to pass through them and are called Selectively Permeable (or semi-permeable)

A cell does NOT need to use energy to move particles from areas of high concentration (crowded) to areas of low concentration (less crowded). This type of movement is called diffusion.

Osmosis the diffusion of WATER through a cell membrane

Some substances enter and leave a cell by passing through protein doorways, also called channels. Passive transport High to low; NO energy is required. Active Transport Low to high; energy IS required (ATP)

Under Flaps Passive transport Active Transport The movement of particles from areas of high concentration to areas of low concentration through protein doorways. Active Transport The movement of particles from areas of low concentration to areas of high concentration with the use of energy.

All cells live in a liquid environment in which materials such as salts and gases are dissolved.

* Concentration * Equilibrium How crowded together the particles of these materials are in a liquid * Equilibrium When the concentration of particles is the same inside and outside the cell

There’s a higher concentration of particles outside the cell than inside. Particles move into the cell. The concentration of particles is the same inside & outside the cell (equilibrium).

There’s a higher concentration of particles inside the cell than outside. Particles move out of the cell. The concentration of particles is the same inside & outside the cell (equilibrium).

Particles that are too large to pass easily through the membrane can enter a cell by endocytosis. Once the particle is completely surrounded, a vesicle pinches off. The cell comes in contact with a particle. The cell membrane begins to wrap around the particle

Large particles can leave a cell by exocytosis. (exit) Large particles that must leave the cell are packaged in vesicles The vesicle travels to the cell membrane and fuses with it The cell releases the particles into the environment