Cell Membrane: Description of Substance Movement and Relation to Structure

This article discusses the movement of substances across the cell membrane through diffusion, osmosis, active transport, and phagocytosis. It also explains how the exchange of material is related to the structure of the cell membrane. The cell membrane is selectively permeable and allows some substances to pass through while preventing others. The type of protein transport present in the cell membrane determines the substances that can pass through it.

TASK 16 CELL
MEMBRANE

Table of Contents
MAIN BODY...................................................................................................................................3
1. Description of the movement of substances across the cell membrane...................................3
2. The ways in which exchange of material across the cell membrane is related to its structure
......................................................................................................................................................5
REFERENCES................................................................................................................................1

MAIN BODY
1. Description of the movement of substances across the cell membrane
Diffusion
Diffusion can be described as a method through which the substances move around the
membrane. In this process, the molecules move from one place to another but specifically from a
high concentration area to a low concentration region within the body of an individual. The
major reason behind this process is that the molecules collide with each other and gives rise to
the process of diffusion within an individual (Dhariwal and Nichol, 2021). Diffusion can be
referred to as a movement that can take place at any time within the body of a person and depicts
a candid movement of the molecules downwards which is referred to as concentration gradient.
The diffusion takes place because, it is the basic nature of molecules to move from a high
concentration region to a low concentration area. For instance, when a drop of a colour meets the
surface of a beaker of water, the process of diffusion takes place and suddenly all the molecules
in the beaker starts spread and change the colour of the water.
Osmosis
Osmosis is also a method through which the substances flow and moves across the
membrane within the body of a human being. The process of osmosis is different from the
process of diffusion. However, it can be described as the flow of water one place that is high
concentrated area to another that is a low concentrated area inside the human body. The process
of osmosis takes place beside a membrane that is semipermeable. A semipermeable member
refers to a membrane which only allows specific molecules to pass beside that membrane and
restricts the other molecules to pass from the same (Zhao and et.al., 2021). The process of
osmosis only includes water molecules. For instance, if a beaker has a semipermeable membrane
within, then it will divide the molecules within the beaker into two parts. In both the parts, the
water level remains same, however, it has been noted that concentration levels on both the sides
are different which leads to the process of osmosis. Similar, is the process of osmosis within a
human body.

Active transport
A process through which the dissolved molecules move from a place of high
concentration to a place having low concentration can be referred to as the process of active
transport. This process of active transport takes place within the human body and allow the
molecules to move beside the membrane. This is also a method of transportation of molecules
from one place to another inside the human body (Berlaga and Kolomeisky, 2021). In this
process, the atoms move against the concentration incline with the help of the energy that
releases during the process of respiration. Most of the times, it has been noticed that the
dissolved atoms are present in a high concentration region within the human body than they
place themselves outside because the living beings require these atoms and there is a need of the
body to absorb these.

Phagocytosis
It is a process by which certain living cells known as phagocytes ingest other particles. It
may be a free living one celled organism such as an amoeba or might be white blood cell. This is
a cellular procedure for ingesting and elimination of particles larger than 0.5 μm in diameter
which also includes foreign substances, microorganisms and apoptotic cells. Phagocytosis is
found in many types of cells and thus, it is an essential process for tissue homeostasis. It has
happened as cells have to complete some steps in order to appropriately phagocytize something.
Phagocytosis is a critical part of immune system (Ben-Akiva and et.al., 2020). By destroying the
infected cells, the immune system limits down the ways in which quickly the infection can be
spread and multiply. Moreover, the immune system cells which needs to perform phagocytosis
can utilize other mechanisms as well to destroy pathogens inside the phagolysosome.
2. The ways in which exchange of material across the cell membrane is related to its structure
The cell membrane is one of the great multi tasker of biology. This provides structure for
the cell and protects cytosolic contents from the environment along with allows cells to act as
specialized units. All cells are boxed in by a cell membrane which is selectively permeable.
Molecules are the ones who move in and out of cells with the help of diffusion as well as active
Phagocytosis
Source: (BioDifferences, 2020)

transport (Sevencan and et.al., 2020). Cells are able to loss and gain water with the help of
osmosis. Cell membrane has two structures which has been represented in the below diagram:
Source: (Bitesize, 2022)
In the above diagram, the extracellular environment is the area which presents outside the
cells. Within this each layer has two main components such as proteins and phospholipids. They
have been arranged into two layers and are able to move around within the layers and give
flexibility to the cell membrane. Among the two layers of phospholipids, protein molecules have
been found those are embedded into those two layers. Membrane proteins have a wide variety of
functions to perform. Some of them allows the cell to respond as per specific chemical signals
from other cells while others are enzymes as well as some proteins that are involved into the
transport of substances all across the cell membrane.
The cell membrane is selectively permeable through which some substances pass through
more slowly but prevents other substances as well passing through it. Some of the small
molecules which includes water, carbon di oxide and oxygen pass directly through the
phospholipids into the cell membrane. Large molecules such as glucose requires a specified
transport protein in order to facilitate their movements. In addition to this, the type of protein
transport presents into the cell membrane determines the substances that the membrane is
permissible to (He, Zhang and Feng, 2020). Then molecules move into and out of the cells with
the help of process known as diffusion. After that cells can gain and loss water by osmosis which
is a movement of solvent particles from a solution that is diluted to more concentrated one. After

this, the active transportation occurs all across the cell membrane from the area which have low
concentration. This basically transport protein called sodium potassium pump.

REFERENCES
Books and journals
Ben-Akiva, E. and et.al., 2020. Biomimetic anisotropic polymeric nanoparticles coated with red
blood cell membranes for enhanced circulation and toxin removal. Science
advances, 6(16), p.eaay9035.
Berlaga, A. and Kolomeisky, A.B., 2021. Molecular Mechanisms of Active Transport in
Antiporters: Kinetic Constraints and Efficiency. The Journal of Physical Chemistry
Letters, 12(39), pp.9588-9594.
Dhariwal, P. and Nichol, A., 2021. Diffusion models beat gans on image synthesis. Advances in
Neural Information Processing Systems, 34.
He, Z., Zhang, Y. and Feng, N., 2020. Cell membrane-coated nanosized active targeted drug
delivery systems homing to tumor cells: a review. Materials Science and Engineering:
C, 106, p.110298.
Sevencan, C. and et.al., 2020. Cell membrane nanotherapeutics: from synthesis to applications
emerging tools for personalized cancer therapy. Advanced Therapeutics, 3(3),
p.1900201.
Zhao, S. and et.al., 2021. Engineering antifouling reverse osmosis membranes: A
review. Desalination, 499, p.114857.
Online
BioDifferences, 2020. [Online]. Available Through: <https://biodifferences.net/difference-
between-pinocytosis-and-phagocytosis/>.
Bitesize, 2022. [Online]. Available Through:
<https://www.bbc.co.uk/bitesize/guides/zqdhjty/revision/7>.
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