Fluid Mosaic Model: Structure and Components of Cell Membrane

Running head: BIOLOGY
BIOLOGY
Name of the Student:
Name of the university:
Author note:

BIOLOGY1
2.1 Fluid Mosaic Model
The cell membrane is also commonly termed as plasma membrane is defined as the
biological membrane, which divides the interior part of the cell from the exterior or outside
environment. The primary function of the plasma or cell membrane is to safeguard the cell
from any of the external stimuli or surroundings thus providing the cell with relevant shape
and protect the cell membrane potential (Nicolson 2016). The most widely accepted plasma
membrane model is known as Fluid Mosaic Model that was recommended in 1972 and
describes the behaviour and structure of plasma membrane. Fluid mosaic model explained
that plasma membrane is the crucial part of the model that comprise of cholesterol, proteins
and phospholipids.
Source: (Nicolson 2016)
The basic components present within the plasma membrane are proteins, carbohydrates
and lipids (cholesterol and phospholipids), which is attached to the proteins and the lipids.
 Phospholipid is defined as the lipid that is made up of phosphate-connected head
group, glycerol and two distinct fatty acid tail. The arrangement of membrane consist
of two distinct phospholipid layer with the tails aiming inwards, commonly termed as

BIOLOGY2
phospholipid layer. They are amphipathic in nature and thus consist of both
hydrophobic and hydrophilic regions (Shi et al. 2018). This layer result in interaction
that act as the barrier between the exterior and the interior part of the cell and allow
water and charged substance to easily pass through the membrane.
Source: (Shi et al. 2018)
 Cholesterol is a type of lipid that is made up of four distinct yet merged carbon rings
and is located beside phospholipid within the core membrane (Bassereau and Sens
2018).
 Proteins are extended towards plasma membrane and cross the complete membrane.
The proteins are attached loosely either in the outside and the inside the membrane.
There are two primary membrane proteins namely peripheral and integral membrane
proteins and permit the small ions and molecules to easily pass through the
membrane.
 Carbohydrates group is present solely on the exterior area of the cell membrane and
the present carbohydrates are binded to the proteins thus forming glycoproteins but
since the carbohydrates are binded to the lipid it is commonly known as the glycolipid
(Mouritsen and Bagatolli 2016). They act as the cellular markers that is very crucial
for the immune system thereby allowing the cells to differentiate among the body
cells.

BIOLOGY3
2.2 A
 Diffusion: Diffusion is defined as the physical process exhibiting net transport of
specific molecules and fragments from the lower concentration area to the higher
concentration region. The diffusion material can be either solid, gas or liquid in nature
and the presence of concentration gradient is principle in diffusion (Whiten, Caldwell
and Mesoudi 2016). Example of diffusion in chemical process includes dissolving of
sugar crystal in glass of water. The crystals of sugar present in the glass of water
slowly dissolves because of the clear movement of sugar molecules or psrticles in the
water as the concentration of sugar crystal is denser as compared to water, hence,
sugar crystal molecule transport to the water (Ghez 2018).
Source: (Ghez 2018)
 Osmosis: Osmosis is defined as the class of diffusion where the molecules transport
from the area of higher concentration gradient to the lower concentration of gradient.
In case of osmosis, the molecules have to cross the semi-permeable membrane that

BIOLOGY4
will balance the concentration gradient that happens spontaneously (Chung et al.
2015). There are three types of osmosis namely isotonic, hypertonic and hypotonic
depending on the level of solvent and the solute. Example of osmosis includes the
process through which the plants captivates water from the soil. The plant roots
consist of high solute concentration as compared to the soil therefore, the water flows
inside the roots of the plant (Odom, Barrow and Romine 2017).
Source: (Chung et al. 2015)
 Active transport: In active transport, the particles transport from the area of lower
concentration to the region of higher concentration ad is considered as the opposite
mechanism of diffusion where the molecules moves against the concentration gradient
(Gerike and Parkin 2016). The mechanism of active transport is called as active as
high amount of energy is required by the molecules to transport from one
concentration gradient to another concentration gradient. Example of active transport
includes movement of stone to uphill that consist of stone movement from lower
concentration area towards higher concentration area (Buchanan et al. 2018).

BIOLOGY5
Source: (Gerike and Parkin 2016)
 Bulk Transport Work: Bulk transport work is defined as the mechanism where large
particles move across the complete cell membrane. In this process the substance
transport individually in the form of small pieces and later fuse together to transport
across the membrane (Nikonenko et al. 2019). There are four different types of bulk
transport namely pinocytosis, exocytosis, phagocytosis and receptor-facilitated
endocytosis. Example of bulk transport include macrophages. Macrophages engulf the
pathogen by extending its arms around the pathogen and later enclosing it within the
membrane sphere called as food vacuole. Therefore, in case of bulk transport, the
molecules are selectively grabbed and communicated (Tarahomi et al. 2017).