Definition: What is the Cytoplasm?
In
cell biology, the cytoplasm is a highly viscous (gel-like) substance enclosed
within the cell membrane. It is composed of water (about 85 percent), proteins
(10 to 15 percent), lipids (2 to 4 percent), nucleic acids, inorganic salts and
polysaccharides in smaller amounts.
Depending
on the cell, cytoplasm may also contain occasional granules of inclusions (e.g.
stored nutrients and pigments, etc). Apart from the cell membrane, which
encloses all cell components, a majority of cell organelles (ribosome, Golgi apparatus, Endoplasmic Reticulum, etc) are located in the
cytoplasm. For this reason, most of the metabolic activities occur within the
cytoplasm.
* Organelles
are also part of the cytoplasm.
* The
cytoplasm makes up nine-tenths of the entire cell.
Some
of the other functions of the cytoplasm include:
- Maintain the shape of a cell
- Cell movement
- Material exchange
Recent
discoveries regarding the cytoplasm:
· Depending
on the activity, bacterial cytoplasm can display glass-like properties.
· Yolk
segregation from the cytoplasm in fish embryo is crucial for the development of
fish larva.
· The
"atypical centriole" in the cytoplasm has been associated with infertility,
birth defects, and miscarriages.
· Different
cell organelles have a different "feel" or experience in the
cytoplasm.
Location
As
previously mentioned, the cytoplasm is enclosed within the cell membrane as is
the case with the other cell components/organelles. With regards to the
specific location, however, this is dependent on the type of cell. For
instance, in eukaryotic cells, the cytoplasm is located between the cell
membrane/plasma membrane and the nuclear membrane.
Unlike
prokaryotic cells, eukaryotic cells contain a membrane-bound nucleus.
This nuclear envelope separates the nucleus from the other parts of the cell.
As a result, the cytoplasm is restricted to the space between the nuclear
membrane and the cell membrane.
Prokaryotes,
on the other hand, lack a true nucleus (DNA material contained in a nuclear
membrane). As a result, there is no nuclear membrane separating genetic
material (DNA) from the other components of the cell.
In
prokaryotes, then, the cytoplasm occupies the entire cell environment (within
the plasma membrane). In this case, all cellular components/organelles,
including the genetic material, are suspended in the cytoplasm.
With
regards to location, the cytoplasm is also divided into the two layers. These
include the ectoplasm and the endoplasm. For the most part, the two are used to
describe the cytoplasm of protozoa (amoeba in particular) that varies in
structure, location, and function.
Ectoplasm -
This is the outer layer of the cytoplasm in a eukaryotic cell (amoeba). As
such, it is located just beneath or adjacent to the plasma membrane. In such
cells and amoeba, this layer of the cytoplasm is clearly visible given its
location.
Some
of the main characteristics of the ectoplasm include:
- Non-granulated
- Less dense and thus more clear
- Thin and superficial
- Contains actin filaments in higher numbers (this
provides the cell membrane with elastic support)
In
amoeba, the ectoplasm plays an important role in locomotion. This is achieved
through changes in the acidity and alkalinity of water in the ectoplasm.
Here,
changes in alkalinity/acidity of the water cause the amount of water in the
pseudopodium to change. As a result, the organism changes direction depending
on the elongation or shortening of pseudopodium as a result of the
concentration of water.
Endoplasm -
Unlike the ectoplasm, the endoplasm is the inner layer of the cytoplasm. As
such, it is located deeper in the cell where it surrounds the nucleus. It
contains many granules (secretory vesicles) and is, therefore, denser compared
to the ectoplasm.
- Amino acids
- Carbohydrates
- Lipids
- Enzymes
- Water
- Inorganic Ions
- Various molecular compounds
Given
that the endoplasm contains many of the organelles of the endomembrane system;
it is the site of most of the processes that occur in a cell. As such, it
significantly contributes to the various metabolic activities of the cells as
well as cell division.
Like
the ectoplasm, the endoplasm also plays an important role in locomotion. Here,
the endoplasm flows and fills pseudopodium where it's converted into ectoplasm.
Change
in the alkalinity or acidity of this fluid then changes the concentration of
water making it possible for the organism to move in a particular direction
(depending on the location of food substances).
As
the ectoplasm in the pseudopodium cause the amoeba to move in one direction,
ectoplasm at the tail end is slowly converted to endoplasm that contains more
granules. This allows the cycle to continue making it possible for the organism
to change direction depending on its needs.
Definition of Terms
Cytosol -
The cytosol is the intracellular fluid of the cytoplasm. It is largely composed
of water (over 70 percent) and surrounds all organelles located/suspended in
the cytoplasm. Some of the other components of cytosol include soluble
molecules of varying size, proteins as well as dissolved ions.
- 7.0 -7.4 pH range
- Viscosity similar to water
- Less than 0.0002 mM of calcium ions concentration
- High amount of charged macromolecules
Functions:
As
the intracellular fluid of the cytoplasm, the cytosol is involved in signal
transduction originating from the cell membrane. It contributes to the
transduction signaling from the plasma membrane to the nucleus (with the
nucleus being the effective site).
Apart
from its role in signaling, the cytosol is also involved in the transportation
of metabolites (e.g. amino acids in eukaryotic cells) in addition to being the
site of metabolic chemical reactions in prokaryotes.
* The
difference between cytoplasm and cytosol lies in the fact that cytosol is the
fluid (intracellular fluid) of the cell while cytoplasm consists of all cell
components within the cell membrane (excluding the nucleus).
Nucleoplasm -
Also known as the karyoplasm and nucleus sap, the nucleoplasm is a type of
protoplasm contained within the nuclear membrane.
Like
cytosol, nucleoplasm is largely composed of water, various molecules as well as
dissolved ions. Apart from maintaining the shape and structure of the nucleus,
nucleoplasm is also involved in the transportation of various material required
for cell metabolism and other functions.
* Compared
to cytosol (in the cytoplasm), the nucleoplasm is highly gelatinous.
* Prokaryotic cells do not have a nucleoplasm.
Protoplasm -
Described as the basis of life upon its discovery, the term protoplasm is
sometimes used to refer to the cytoplasm and the internal components of a cell
in general. It consists of proteins, lipids, sugars, and starches
(carbohydrates), phosphates, potassium, and sodium (inorganic salts) and water.
* Whereas
cytoplasm includes cell components within the cell (excluding the nucleus) the
term protoplasm is sometimes used to refer to all components within the cell
including the nucleus.
Cytoplasmic Structure
As
previously mentioned, the cytoplasm is mostly composed of water (water is the
largest component). Apart from water, sugars, inorganic salts and other organic
components, the cytoplasm is also composed of various organelles (which also
form the endomembrane system) and the cytoskeleton.
The
endomembrane system is composed of:
- Golgi complex
- Endoplasmic reticulum
- Endosomes
- Lysosomes
- Vacuoles
Cytoskeleton is composed of:
- Microtubules
- Microfilaments
- Intermediate filaments
Different
components of the cytoplasm have different functions that contribute to the
proper functioning of the cell. Whereas the endomembrane systems play an
important role in the transport of various materials, the cytoskeleton serves
to support the structural integrity of the cell.
* Components
of the cytoplasm are in continual flux and thus not stable (fixed in
place).
Functions
Essentially,
functions of the cytoplasm can be attributed to its components. Some
of these functions include:
Transport
The
cytoplasm is involved in several forms of transportation. The endoplasmic
reticulum and golgi apparatus, both components of the endomembrane system, are
some of the systems involved in the transportation of material (proteins and
lipids respectively) from one point to another in the cell.
On
the other hand, the cytoplasm is also involved in the transportation and
consequent removal of waste products from the cells through structures known as
vesicles.
Maintain
the shape and structure of a cell
As
already mentioned, the cytoplasm is a viscous matrix that is largely composed
of water. By exerting an outward pressure (turgor pressure) against the cell
membrane, it contributes to the general shape of the cell.
Apart
from the pressure exerted by the fluid, the cytoplasm also contributes to the
shape and structure of the cell through its cytoskeleton. As mentioned earlier,
the cytoskeleton is composed of microtubules and microfilaments (as well as
intermediate filaments).
As
is the case with the skeletal system in higher animals, the cytoskeleton
contributes to the shape of the cell at the plasma membrane.
Protection
Consisting
of cytosol, a viscous fluid, the cytoplasm protects various components of the
cell by acting as a cushion that absorbs some shock that may otherwise damage
organelles.
Here,
then, the cytoplasm serves to protect the internal components of the cell by
acting as the barrier between the internal and external.
Storage
Various
molecules (lipids, fats, starch, etc) can be found floating in the cytoplasm.
Some of these molecules are used to build different structures of the cells.
Before they are used, however, these molecules float in the cytoplasm where
they are stored.
For
this reason, some cells may contain high levels of given molecules in their
cytoplasm. Adipocytes, for instance, are good examples of cells that store high
amounts of lipids in their cytoplasm.
Site
of metabolic activities
Several
enzymes can be found in the cytoplasm. The cytoplasm, therefore, is also a site
of metabolism for a number of substances. These activities, however, occur at a
higher rate in such organelles as the mitochondria.
* It
is worth noting that like the chloroplast and nucleus, the mitochondria is not part of the
endomembrane system.
Some
of the other functions of the cytoplasm include:
- Cell movement
- Cell
division
- Cell growth
* When
stained with Eosin, in histology, cell cytoplasm will appear pink in color.
Cytoplasm group:
1. Megawati
2. Hairul Rizki Pratama
3. Mita Novanti
4. Intri Haffrayuni
5. Dhea Anggraini
6. Firnandus Tiko
7. Mirandha Aussiemegan Jusaim
8. Rosita Dwi Suryana
Students have to watch this before class: https://www.youtube.com/watch?v=mGEjoNwOab4
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