Exchange of materials across the Cell Membrane

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Exchange of materials across the Cell Membrane
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Exchange of materials across the Cell Membrane
Introduction
The role of a cell is to move substances such as glucose, water, ions, food, hormones and
oxygen across the cell membrane (AlHarbi et al., 2015). Most of these materials cannot pass
directly through the cell membrane; therefore, their transport occurs through specialized proteins.
In general, only small non-polar molecules pass through the cell membrane. For example, gases
like oxygen or carbon dioxide can move through the membrane freely. Different types of
movements that happen across the cell membrane include diffusion, osmosis, active transport
and phagocytosis. This essay will focus on these movements and how they are related to the
structure of the plasma membrane.
Diffusion
Diffusion is the net passive movement of particles from an area of higher medium to that of a
lower medium. The flow of these molecules continues until there is a uniform concentration
throughout. Diffusion is a process that works best with gases or liquids. It is faster in gases as
particles move faster than in fluids where particles move slowly (Chung et al., 2015). Diffusion
is as a result of the collision of molecules, and an example of this is when food coloring
molecules interact with water molecules, causing the colorings to move around the glass
randomly. The molecules spread out over space as collisions continue. Diffusion occurs when
particles are spread and free to move. Besides, diffusion is an essential activity in human organs
where chemicals and gases move in and out of cells. Human organs where diffusion occurs
include; the lungs where oxygen and carbon dioxide move in and out and in kidneys where
movement of water, salts and waste products occurs (Chung et al., 2015). Change of calcium

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from food into cells in the intestines is also an example of places diffusion occurs in human
organs.
Importance of diffusion
 It helps molecules enter the body and wastes get eliminated.
 It helps in movement of digested food materials from the intestine through the blood.
Osmosis
It is the process by which water molecules pass through a semipermeable membrane from a
solution of high to low concentrations (Dixon, 2015). Osmosis is passive transport since it does
not require the application of energy. An examples of a perfect solvent is water while a living
tissue can be used as a semipermeable membrane. Osmosis balances the concentrations of solute
on interior and exterior sides of a membrane. It occurs when a partially permeable membrane
separates two solutions. Osmosis accounts for many functions that maintain life. Presence of cell
wall in plant cells makes them remain turgid when placed in pure distilled water. Unlike the