Transcript Passive and Active Transport
Passive and Active Transport
Movement of Material through the Cell Membrane
Each individual cell exists in a environment.
liquid
The presence of a liquid the cell.
environment
makes it easier for materials such as food, oxygen, and water to move into and out of There are several ways in which materials enter and leave the cell.
Two types of Passive Transport: Diffusion and Osmosis
Diffusion
Diffusion is the process by which molecules of a substance move from areas of higher concentration (more particles) of that substance to areas of lower concentration (less particles).
Examples: Food color in water Air freshener in house Dry erase cleaner
What determines whether diffusion occurs through a membrane?
1) If two substances are present at unequal amounts on either side of the membrane, each substance will tend to move towards the area of lower concentration until equilibrium is reached (same amount of particles on both sides).
2) The permeability of the membrane. (allows substances to diffuse across the membrane)
Note
A membrane is said to be impermeable to those things that cannot pass across it. Biological membranes are semi-permeable (cell membrane). They are permeable to some substances and impermeable to others.
Facilitated Diffusion
Many molecules are transported across a membrane in the direction of the lowest concentration by a carrier protein.
For example: In red blood cells, a carrier protein in the cell membrane transports glucose from one side of the membrane to the other.
The glucose transporter protein facilitates, or helps in the diffusion of glucose.
Osmosis
The diffusion of water through a selectively permeable membrane from an area of high concentration of water to an area of low concentration.
For example if you place a concentrated sugar solution on one side of a semi-permeable membrane and a dilute sugar solution on the other side. The result is the net movement of water through the membrane from the side with the
dilute
sugar solution to the side with the concentrated sugar solution.
Note
If, however two solutions contain
exactly
the same amount of dissolved material, there is no
osmotic
pressure across the membrane
separating
them because the concentrations of dissolved
materials
are in equilibrium.
Normal blood
cells will shrink if to much water leaves the cells due to osmosis. If to much water enters the cell during osmosis the red blood cell will swell.
If the amount of water that enters the cell is not
regulated
, then eventually to much water will enter the cell and it will burst.
Osmosis and Diffusion energy
are forms of
passive
transport across the cell membrane because is not needed for these processes.
Active Transport
Active transport
is an
energy
-requiring process that enables materials to move
across
the membrane
against
difference.
the concentration Think of a unicyclist going up hill, requires more energy then going down hill
There are two types of Active Transport
1) Individual membrane-associated pumps in the membrane. Molecules include calcium,
potassium chemical molecules
are carried through the
cell
, and sodium and require energy.
2) Large amount of materials are
transported
through the movement of the cell membrane
Endocytosis
: is the process of taking
material
into the cell by means of of
food
this way.
infoldings
or pockets of the cell membrane. Large molecules, clumps , and even whole cells can be taken up in
Phagocytosis cytoplasm
food.
: large particles taken into the cell by endocytosis. In phagocytosis, extension of surround and engulf
large
particles. Amoebas use this method to take in
Endocytosis
Pinocytosis
: process of taking up
liquid
form the surrounding
environment
by cells. Tiny pockets form along the cell
membrane
, fill with liquid, and pinch off from
vacuoles
within the cell.
Exocytosis: The removal of means of a contractile vacuole, along with removal of
large
material.
water
by