Cell Membrane Transport Processes

This assignment delves into the fascinating world of cell membrane transport. It examines various processes like diffusion, osmosis, active transport, and phagocytosis, explaining how they facilitate the movement of molecules across the cell membrane. The discussion highlights factors influencing these processes, such as temperature, molecule size, concentration gradients, and the role of ATP in active transport. The importance of the plasma membrane in regulating cellular functions and maintaining homeostasis is also emphasized.

Health Professions

TABLE OF CONTENTS
TASK...............................................................................................................................................3
4.1 Movement of substances across the cell membrane..............................................................3
4.2 Exchange of materials and relation with cell membrane structure........................................4
REFERENCES................................................................................................................................6
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TASK
4.1 Movement of substances across the cell membrane
Cell membranes are like closed wall that surround the cells for separating the interior and
exterior atmospheres. It is also called as plasma membrane. Following processes take place
across the plasma membrane when movement of different substances are considered:
Diffusion: Often the cell membrane experiences a change or difference in the
concentration when comparing inner and outer potentials. This potential is considered as
chemical potential and the movement of substance across the cell is completely dependent on
this increase or decrease of concentration. The particles that are accumulated in the outer area of
cell randomly move around and slowly mix up with cell constituents (Stein, 2012). There can be
mass or bulk transportation when chemical potential outside the cell is more. The diffusion
mechanism is totally dependent on the pressure gradient which changes according to the
concentration.
Osmosis: The conditions in which there is no balance or equilibrium in the concentration
of solvents the process of osmosis takes place. The molecules of the external elements travel
from the area of higher concentration to the lower ones with a purpose of reaching the
equilibrium position (Stein, 2012). The membrane across which osmosis takes place is called the
semi-permeable membrane. It means that only some of the solvents or fluids are allowed across
this membrane. There are three types of osmosis which take place and these are hypo-tonic,
isotonic and hyper-tonic. Here, hypo-tonic is the movement of fluids from inside to outside the
cell while hyper-tonic is the movement of fluids from outside to inside of the cell. On the other
hand, isotonic is the process of continuous movement of fluid inside and outside i.e. a balanced
condition (Sherwood, 2015).
Active Transport: There are situations in which molecules or cells move from lower
concentration to the region where higher concentration is present. The direction of motion of the
subject from lower to higher concentration is usually against certain type of concentration
gradient. The energy for this movement is gathered from respiration and there are certain
chemical changes taking place inside the cells (Stein and Litman, 2014). Protein carriers act as
the transporters or the agents that help in aiding this process. There is another kind of transport
i.e. passive transport which involves kinetic energy and natural entropy of the molecules that are
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moving. Ions, glucose and certain types of amino acids are the substances that are actively
transported across the cell membranes.
Phagocytosis: The process in which cell also referred to as a phagocyte creates an
internal compartment for engulfing a solid or a particle. This internal compartment is referred as
phagosome. The inclusion or acquisition of nutrients takes place in the cell through this process.
This type of movement across the plasma membrane is witnessed when pathogens or debris are
to be removed from the cells especially by the immune system (Alberts and et. al., 2013). There
are some objects like bacteria, dead tissue cells and small mineral particles which are
phagocytized that means for their transportation
4.2 Exchange of materials and relation with cell membrane structure
Cell membrane or the plasma membrane is an important part of the cell. It helps in
diffusion of cell fluids to the external environment and restricts the unwanted flow of
constituents. The entire exchange and control of messages or materials across the cell is under
control of plasma membrane. There are different elements which form the structure of plasma
membrane and these include phospholipids, proteins, glycoproteins and glycolipids (Stein,
2012). The aforementioned processes which take place in and around the cell are affected by
some conditions or changes in the structure of the cell membrane.
Diffusion is affected when temperatures, surface area and the types of molecules vary.
This implies that when temperature is quite high due to rise in the kinetic energy then molecules
move faster. The diffusion process is instigated and mixing up of fluids is faster. On the other
hand, molecule size impacts the process rate. For instance, if a large molecule is trying to diffuse
with the cell then significant decrease in speed can be experienced. Osmosis is considered as a
special type of diffusion which is affected by the water and pressure potential that is present in
the cell and the surroundings (Stein, 2012). Permeable membrane has to change its allowance
capabilities according to the level of concentration or potential of the surroundings. Cells shrink
in case of hyper-tonic conditions while swell in case of hypo-tonic conditions. It is the plasma
membrane that controls or operates the physical conditions or osmosis in the cell.
Active transport as mentioned before is a process of actively moving fluid or constituent
from a lower concentration to a higher concentration. ATP is the energy supplier in case of
active transport. It is Adenosine triphosphate which is also referred as the protein carrier enzyme.
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There are certain materials that may or may not move through the bilayer because of plasma
membrane conditions. In these conditions, the active transport takes place and certain changes
take place in the shape with help of bilayer protein transports.
Phagocytosis is also a process which takes place whenever movement of transportation of
some sort of fluids or solvents is considered. Often bacteria or one unit cell organisms are
accumulated by the cells due to phagocytosis. The most important component of this complete
process is the adherence (Yeagle, 2016). If particle or solid granular structure which is to be
intact with the cell is not adhered then a surface film is developed over the bacteria due to protein
elements i.e. opsonins. This further creates a difficulty for the cell membrane to engulf the
particle because it is accumulated with these surroundings. Hence, it is not easy for any sort of
fluid or particle to get transported in the cell without any restrictions. The presence of cell
membrane makes it easier and difficult to change the structure of cell depending completely on
the type of fluid that has been introduced (Stein and Litman, 2014).
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REFERENCES
Books and Journals
Alberts, B. and et. al., 2013. Essential cell biology. Garland Science.
Sherwood, L., 2015. Human physiology: from cells to systems. Cengage learning.
Stein, W. D. and Litman, T., 2014. Channels, carriers, and pumps: an introduction to membrane
transport. Elsevier.
Stein, W., 2012. The movement of molecules across cell membranes (Vol. 6). Elsevier.
Stein, W., 2012. Transport and diffusion across cell membranes. Elsevier.
Yeagle, P. L., 2016. The membranes of cells. Academic Press.
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