Structure and Function of Cell Membrane: A Comprehensive Overview

This article provides a comprehensive overview of the structure and function of the cell membrane. It discusses the fluid mosaic model, phospholipids, proteins, and other components of the membrane. It also explores the role of cholesterol and carbohydrates in the membrane. Perfect for students studying advanced cell biology.

Running head: ADVANCED CELL BIOLOGY
ADVANCED CELL BIOLOGY
Name of the student:
Name of the university:
Author note:

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Introduction:
The cell membrane is said to have a main role in working for the cell as guarding
system between the single-celled organism and the ecosphere (Kosmalska et al. 2015). It is
believed that it has an important role for the cells to have different type of appearance which
gives permission to the cells to conduct communication with the cell membrane and the area
outside. The membrane of the cell is basically seen to be having a duple layer structure of
phospholipids which are fat-like substances having phosphorus in it (Sezgin, Levental, Mayor
and Eggeling 2017). Every layer of the membrane is made up of phospholipid particles which
has a hydrophilic head and a hydrophobic end tail (Ruan et al. 2016). The proposal of fluid
mosaic model was given just to describe the structure of the cell’s plasma membrane
structures as mosaic of different components (Zalba and ten Hagen 2017). The mosaic is
build-up of the phospholipids, proteins, cholesterol, and carbohydrates which all together
gives the plasma membrane a fluid nature. The assignment will focus on the fluid mosaic
model and interesting facts of the structure of the cell membrane (Shan and Wang 2015).
Figu
re1: Cell Membrane

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(Source: Shi et al. 2018)
Structure of the cell membrane:
The cell membrane is seen to be a bunch of various types of proteins and lipids (Loew
2018). The lipids have an ability to make up wherever it is necessary from 20 percent to 80
percent of the cell membrane focusing on the location of the membrane and its role in the
cell, and also keeps the proteins as remainder (Harrison 2015). The lipids play a major role in
making the membranes flexible, whereas the proteins assess and regulates the chemical
climate of the cell and assist them in the moving out of the molecules through the membrane
(Xuan et al. 2016).
Phospholipids
Phospholipids builds the main structure of the cell membrane. Every single molecule
of a phospholipid consists of two different ends which is a head and a tail end (Fang, Kroll,
Gao and Zhang 2018). The head has the composition of a phosphate group which is in love
with the water which means that the molecule has a tendency to get attracted towards water
molecules and is called hydrophilic (Chen et al. 2016). Whereas the tail end is made up of
two threads of hydrogen atoms and carbon atoms which all together is called fatty acid chains
(Deisseroth et al. 2016). These fatty acid chains are scared of water or hypdrophobic which
states that they have a tendency to run away or avoid water molecules (Abedini, Schmidt and
Raleigh 2016). The concept of hydrophobicity is similar to the condition which happens
when oil droplets fall in to water. It is observed that the oil never mixes with water (Tan, Wu,
Zhang and Zhang 2015).

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Figure 2: what are phospholipid also known as
(Source: Sezgin, Levental, Mayor and Eggeling 2017).
The cell membrane is seen to have a composition of the sterols and glycolipids. One
of the most important sterol is the cholesterol, which has a major role of regulating the
flexibility of the cell membrane present in the animal cells (Zhou et al. 2015). It has been
found that decreased composition of cholesterol present in the cell membranes makes it more
fluid in nature, but it also increases its permeability to other molecules (Abedini, Schmidt and
Raleigh 2016). It can be said that the total amount of cholesterol composition in the
membrane is functions to maintain the cell’s permeability thus making it capable to permit
the entry of the exact amount of molecules (Vance 2015).

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Figure 3: Structure of the cell membrane
(Source: Tatsuta and Langer 2017)
Fluid mosaic model:
The fluid mosaic model has been said to be a cell membrane structure which has a
tendency to act as a two- dimensional structured liquid consisting of various type of mixed
composition (Nicolson 2016). The cell membrane has been explained to be fluid in nature
because of the component’s hydrophobic nature which are embedded inside the membrane
structure (Frontera and Ochala 2015). These items are the lipids and the membrane proteins
which interchange sideways all over the membrane (Dagnino 2015). The fluid mosaic model
was developed in order to describe the structure of the cell’s plasma membrane structures as
mosaic of different components. The mosaic has the materials such as the phospholipids,
proteins, cholesterol, and carbohydrates which all together provides the plasma membrane a
fluid nature (Shi et al. 2018). The heads of the outmost level witnesses and acts along with
the outside environment which is watery in nature. Whereas, the heads of the molecules
present into the interior layer focuses inward and operates with the watery state of the
cytoplasm of the cell (Bassereau and Sens 2018). The portion present in between the outer
and inner layers is found to be fluid repellent, as it has the capability of splitting the inside
portion of the cell from the outer surrounding. The nature of the cell membrane is observed to
be semipermeable which develops a condition where only selected molecules can pass inside
or outside the cell (Mouritsen and Bagatolli 2015).

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Figure 4: Fluid Mosaic Model
(Source: Nicolson 2015)
Facts about the cell membrane:
 The membranes are having a lipid double layer which is fluid in nature, with the
condition of proteins distributed around in a surrounding manner (Phillips and Voeltz
2016).
 The phospholipids can be said to build the lipid bilayer. The phospholipids segregate
altogether in a manner forming the double layer because of the fact that out of the two
ends, one has nature to get attracted towards water while the other repels water
(Frontera and Ochala 2015).
 This arrangement is known as the Fluid Mosaic Model (Abedini, Schmidt and Raleigh
2016).

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 These proteins also function as pumps or pores as it initiate and help the molecules to
entre or get out of the membrane (Reading et al. 2017).
 They also control the manner and nature of molecules to enter inside and go outside
of the cell (Sezgin, Levental, Mayor and Eggeling 2017).
 Carbohydrates acts as receptors in some conditions as they remain attach to the
proteins (Watson 2015).
 The fluidity of the cell membrane is explained simply where it states that fluidity is
the capability of the membrane to faultlessly part and generate space whenever a
molecule or particle enters and also when the molecules passes the cell membrane, the
membrane effortlessly later streams back in the original position and ends the gap
which was earlier created (Yu et al. 2018).
 The cells of the animal are found to have cholesterol implanted inside of the
hydrophobic portion of the plasma membrane (Weigele et al. 2017). The condition
states that apart from the fact that as the tail end of the phospholipid molecule attempt
to custom condensed stuffing with the droplet in the temperature, the implanted
cholesterol molecules are observed to prevent the condition from taking place, by
sustaining the fluid nature of the cell membrane (Frey, Ziebertn and Schwarz 2019).
 It has also been observed that at conditions of higher temperatures, the cholesterol
molecules avert the extra fluid nature by essentially decreasing the fluidity of the
molecule. Thus it states that the cholesterol molecules play a vigorous role in the aim
of maintaining the healthy and purposeful fluidity of the molecules (Tsai et al. 2017).

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Figure 4: Cell Membrane Composition
(Source: Phillips and Voeltz 2016)
Questions regarding the cell membrane:
1. Carbohydrates present in the cell membrane donate to which of the following?
 Cell to cell adhesion
 Fluidity
 Structure
 Protection
Answer:
2. The Fluid Mosaic Model defines proteins as_____.
 bound to the carbohydrates
 bound to one residence in the membrane
 moving laterally all over the space
 as present only on the cytoplasmic adjacent of the cell

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 as hydrophobic and hydrophilic particles
Answer:
3. Which of the following is contributes in the cell communication?
 Protein
 Cholesterol
 Phospholipid
 Cytoplasm
 Carbohydrate
Answer:
Conclusion:
The Cell-Membrane is an interesting matter to talk about as it has been observed to be
entirely present surrounding the cells and also serves by maintaining their interiors portion
separate from the outer surrounding. The cell membrane is a collection of fat particles with
the hydrophobic tails which has the nature to repel water, and also a hydrophilic head which
tends to get attracted towards water. The structure of the membrane is called the
phospholipid bilayer structure. The structure is called a bilayer due to the fact that it is made
up of dual layers of fat molecules, where both has the hydrophobic ends which is facing
interior headed for each other as well as the hydrophilic ends which is embedded fronting
towards the external side of the cell and also hooked on the inside of the cell along with the
cytoplasm. It has been found that decreased composition of cholesterol present in the cell
membranes makes it more fluid in nature, but it also increases its permeability to other
molecules. The cell membrane has been explained to be fluid in nature because of the
component’s hydrophobic nature which are embedded inside the membrane structure.

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