Analysis of Transport Processes: Diffusion, Osmosis, Active, and Bulk

This report provides a detailed overview of four key transport processes: diffusion, osmosis, active transport, and bulk transport. Diffusion is defined as the spontaneous movement of molecules from a region of higher concentration to lower concentration, occurring in gases and liquids. Osmosis invol...Read More

Running head: TRANSPORT PROCESS
Transport Process
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1TRANSPORT PROCESS
Diffusion
The process of diffusion is a spontaneous movement of molecules from a region of its
higher concentration to a region of its lower concentration. Diffusion takes place in gaseous
state or in liquid state (Angius et al. 2015). The diffusion of waste products (carbon dioxide)
during respiration is an example.
Osmosis
The process of osmosis involves spontaneous movement of water molecules across a
semipermeable membrane from a region of low concentration of solute to a region of higher
concentration of solute across the semipermeable membrane. The osmosis movement occurs
until an equilibrium in concentration gradients is reached on either side of the semi permeable
membrane (Kramer and Myers 2013). The phenomenon of osmosis involves only water
molecules and no other solutes in movement; osmosis influences nutrient distribution and
release of waste products in animals. The intake of soil water by plant roots is an example of
osmosis.
Active transport
Active transport involves the transport of the cellular metabolites and ions across cell
membrane against the concentration gradient, which means from a lower concentration to
higher concentration. This requires an input of energy to drive the transport process, usually
ATP is the energy source. This is called primary active transport (Kotyk and Horak 2018).
Another kind of active transport which requires energy from electrochemical gradient is
known as secondary active transport, which involves channel proteins to promote the
transport process. The outflow of sodium ions and influx of potassium ions are coupled
together through primary active transport phenomenon, which occurs through sodium-

2TRANSPORT PROCESS
potassium pump and requires ATP energy to facilitate the transport process. The transport of
glucose ions across proximal convoluted tubule is an example of secondary active transport.
Bulk transport
The macromolecules like hormones, proteins, polysaccharides move in and out of the
cell through an energy requiring transport process called bulk transport. Exocytosis and
endocytosis are bulk transport processes (Wu et al. 2014). The export of toxic products from
a cell through vesicles is an example.
Comparison
Diffusion Osmosis Active transport Bulk transport
This involves
movement of
molecules along
the concentration
gradient.
This involves the
movement of only
water molecules or
solvent; no solute
movement occurs.
This involves the
transport of molecules
and ions against the
gradient of
concentration.
This involves transport of
macromolecules such as
hormones, polysaccharides
and proteins. These are
exported or endocytosed
into the cell. Endocytosis,
exocytosis, phagocytosis
are bulk transport
processes.
There is no
requirement of
metabolic energy
for transport
(Angius et al
2015).
Solvent movement
does not require an
input of energy.
This is an energy
intensive transport
process. The ATP serves
as the source of energy
for primary active
transport whereas the
This is an energy intensive
process requiring an input
of ATP energy to drive the
transport process.

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electrochemical gradient
provides input of energy
for secondary active
transport.
Only solutes and
no solvent
molecules are
required for
diffusion.
Osmosis involves
only solvent
molecules for
movement.
Cellular metabolites and
ions are involved in
active transport process.
Phagocytosis, pinocytosis,
endocytosis and exocytosis
are the different modes of
bulk transport process
which involve biological
macromolecules (Wu et al.
2014).

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References
Angius, A., Balbo, G., Beccuti, M., Bibbona, E., Horvath, A. and Sirovich, R., 2015.
Approximate analysis of biological systems by hybrid switching jump diffusion. Theoretical
Computer Science, 587, pp.49-72.
Kotyk, A. and Horak, J., 2018. Transport processes in the plasma membrane. In Yeast Cell
Envelopes Biochemistry Biophysics and Ultrastructure (pp. 57-72). CRC Press.
Kramer, E.M. and Myers, D.R., 2013. Osmosis is not driven by water dilution. Trends in
plant science, 18(4), pp.195-197.
Wu, L.G., Hamid, E., Shin, W. and Chiang, H.C., 2014. Exocytosis and endocytosis: modes,
functions, and coupling mechanisms. Annual review of physiology, 76, pp.301-331.