Cell Definition
“A cell is defined as the smallest, basic unit of life that is responsible for all of life’s processes.”
Cells are the structural, functional, and biological units of all living beings. A cell can replicate itself independently. Hence, they are known as the building blocks of life.
Each cell contains a fluid called the cytoplasm, which is enclosed by a membrane. Also present in the cytoplasm are several biomolecules like proteins, nucleic acids and lipids. Moreover, cellular structures called cell organelles are suspended in the cytoplasm.
Types of Cells.Prokaryotic Cells
Prokaryotic cells have no nucleus. Instead, some prokaryotes such as bacteria have a region within the cell where the genetic material is freely suspended. This region is called the nucleoid.
They all are single-celled microorganisms. Examples include archaea, bacteria, and cyanobacteria.
The cell size ranges from 0.1 to 0.5 µm in diameter.
the hereditary material can either be DNA or RNA.
Prokaryotes reproduce by binary fission, a form of sexual reproduction.
Eukaryotic Cells
Eukaryotic cells are characterised by a true nucleus.
The size of the cells ranges between 10–100 µm in diameter.
This broad category involves plants, fungi, protozoans, and animals.
The plasma membrane is responsible for monitoring the transport of nutrients and electrolytes in and out of the cells. It is also responsible for cell to cell communication.
They reproduce sexually as well as asexually.
There are some contrasting features between plant and animal cells. For eg., the plant cell contains chloroplast, central vacuoles, and other plastids, whereas the animal cells do not.
Functions of Cell:Provides Support and StructureFacilitate Growth MitosisAllows Transport of SubstancesEnergy ProductionAids in ReproductionCell Membrane
The cell membrane supports and protects the cell. It controls the movement of substances in and out of the cells. It separates the cell from the external environment. The cell membrane is present in all the cells.
The cell membrane is the outer covering of a cell within which all other organelles, such as the cytoplasm and nucleus, are enclosed. It is also referred to as the plasma membrane.
By structure, it is a porous membrane (with pores) which permit the movement of selective substances in and out of the cell. Besides this, the cell membrane also protects the cellular component from damage and leakage.
It forms the wall-like structure between two cells as well as between the cell and its surroundings.
Plants are immobile, so their cell structures are well-adapted to protect them from external factors. The cell wall helps to reinforce this function.What is Osmosis?
Osmosis is a passive process and happens without any expenditure of energy. It involves the movement of molecules from a region of higher concentration to lower concentration until the concentrations become equal on either side of the membrane.
Any solvent can undergo the process of osmosis including gases and supercritical liquids.
Osmotic Solutions
There are three different types of solutions:
An isotonic solution: is one that has the same concentration of solutes both inside and outside the cell.
A hypertonic solution: is one that has a higher solute concentration outside the cell than inside.
A hypotonic solution; is the one that has a higher solute concentration inside the cell than outside.
Effect of Osmosis on Cells
Osmosis affects the cells differently. An animal cell will lyse when placed in a hypotonic solution compared to a plant cell. The plant cell has thick walls and requires more water. The cells will not burst when placed in a hypotonic solution. In fact, a hypotonic solution is ideal for a plant cell.
An animal cell survives only in an isotonic solution. In an isotonic solution, the plant cells are no longer turgid and the leaves of the plant droop.
The osmotic flow can be stopped or reversed, also called reverse osmosis, by exerting an external pressure to the sides of the solute. The minimum pressure required to stop the solvent transfer is called the osmotic pressure
Significance of Osmosis
Osmosis influences the transport of nutrients and the release of metabolic waste products.It is responsible for the absorption of water from the soil and conducting it to the upper parts of the plant through the xylem.
It stabilizes the internal environment of a living organism by maintaining the balance between water and intercellular fluid levels.
It maintains the turgidity of cells.
It is a process by which plants maintain their water content despite the constant water loss due to transpiration.
This process controls the cell to cell diffusion of water.
Osmosis induces cell turgor which regulates the movement of plants and plant parts.
Osmosis also controls the dehiscence of fruits and sporangia.
Higher osmotic pressure protects the plants against drought injury.
