Passive transport is the type of transport of substances across the plasma membrane that takes place without wasting energy.
There is no waste of energy because substances move naturally from the more concentrated medium to the less concentrated one, that is, in favor of the concentration gradient.
Transport of substances takes place until concentrations inside and outside the cell are equalized.
What is the difference between passive and active transport?
In passive transport, no energy is wasted for the displacement of substances. Meanwhile, in active transport, substances travel with energy expenditure.
Learn more about Active Transport.
Types of Passive Transport
There are three types of passive transport: simple diffusion, facilitated diffusion and osmosis.
Simple Broadcast
Simple diffusion is the transport of small, fat-soluble or hydrophobic gases and molecules through the plasma membrane.
Diffusion is a slow process. However, when the concentration differences are too high, the process is accelerated.
An example of diffusion is gas exchange during breathing, as oxygen gas and carbon dioxide are at different concentrations in the pulmonary alveoli.
Learn more about Simple Broadcast.
Diffusion facilitated
Facilitated diffusion is the transport of substances that do not dissolve in lipids. Thus, substances rely on the help of proteins, permeases, to cross the plasma membrane.
Permeses capture substances such as glucose and amino acids and facilitate their entry into the cell.
Learn more about Diffusion facilitated.
Osmosis
Osmosis is a special type of diffusion. It only consists of the passage of water through the plasma membrane.
Osmosis is the passage of water from a less concentrated (hypotonic) medium to a more concentrated (hypertonic) medium.
Learn more about Osmosis.
Exercises
1. (UFPA - PA) - A plant cell placed in a hypotonic medium:
a) will undergo plasmolysis
b) will not undergo any change
c) will be turgid
d) will suffer plasmoptysis
e) there will be water output from the cell
c) will be turgid
2. (UEVA-CE) - The plasma membrane is a selective lipoprotein complex, which enables different concentrations and ionic exchanges between the intra and extracellular media. It is correct to say:
a) Fat solubility and concentration gradient are factors inherent to passive transport.
b) In simple diffusion, the larger the solute molecule, the faster its transport across the membrane.
c) The solute concentration determines the osmotic phenomenon due to the greater permeability of the membrane.
d) In simple diffusion, the rate of transport across the membrane corresponds to the same rate compared to facilitated diffusion.
a) Fat solubility and concentration gradient are factors inherent to passive transport.
3. (UEL) - The movement of amino acid molecules into cells is usually done by
a) osmosis.
b) simple diffusion.
c) facilitated diffusion.
d) active transport.
e) phagocytosis.
c) facilitated diffusion.
4. (PUC - MG) - There is a type of exchange between the cell and the medium that occurs against the concentration gradient and in which the existence of a carrier protein is necessary, whose activation depends on energy expenditure.
This type of exchange is called:
a) Diffusion.
b) Diffusion facilitated.
c) Pinocytosis.
d) Phagocytosis.
e) Active transport.
b) Diffusion facilitated.
See too: Exercises on Plasma Membrane
