[Biology Class Notes] on Competent Cells Pdf

The bacterial cells which will take up the foreign DNA from the environment by a process called transformation are referred to as competent cells. Griffith first reported it in Streptococcus pneumoniae. In the case of wall alteration, E.coli cells are more likely to uptake the DNA. The cells are often made competent by salt and warmth shock therapy. The cells growing rapidly are often made competent more easily than those in other stages of growth. The cells may retain the acquired genetic information after the transformation procedure. The process is essentially used to introduce recombinant plasmid DNA into competent bacterial cells. This process does not require a donor cell but only DNA in the surrounding environment.

Principle of Competent Cells

Competent cells have altered cell walls that allow the DNA to simply undergo it. Some cells got to be exposed to some chemical or electrical treatments to transform them into competent cells. Treatment with calcium ions is the standard method for the preparation of those cells. Electroporation is the process in which cells take up DNA.

Methods of Preparation of Competent Cells

Competence is achieved in two ways:

• Natural Competence

• Artificial Competence

Natural Competence

Bacteria take up DNA from the environment by transformation, conjugation, and transduction. By the process of transformation, the foreign DNA directly enters into the bacterial cell. For this, the cells need to be in a competent state.

Frederich Griffith was the primary one to get natural competence. He injected the smooth strain of pneumococcus in mice, and the mice died. This strain is therefore referred to as virulent strain. But the mice didn’t die when injected with the rough strain (non-virulent strain). Heat-killing abolishes the virulent nature of the graceful strain. The heat-killed smooth strain and therefore the rough strain were mixed. The rough strain acquired the graceful phenotype and has become virulent. This suggests that a heat stable, non-living material obtained from the graceful strain facilitated transformation.

Artificial Competence

In this, the cells are permeable to DNA in the laboratory. The competent cells are often prepared artificially in two ways, namely:

Calcium Chloride: This method was proposed by Mandel and Higa. The bacterial cells were treated with salt then suddenly exposed to high temperatures. This is known as the heat shock treatment method.

Electroporation: During this technique, an electrical field is applied to the cells to extend their permeability. It is also known as electropermeabilization.

What are the Characteristics of Cells?

Every cell consists of a single nucleus and membrane-bound organelles in the cytoplasm. 

Some of the important characteristics of Cells are :

• Cells help in providing structure and support to the body of an organism.

• The cell interior comprises different individual organelles surrounded by a separate membrane.

• The nucleus holds genetic information necessary for reproduction and cell growth.

• Mitochondria is a double membrane-bound organelle that is mainly responsible for the energy transactions that are vital for the survival of the cell.

• Lysosomes digest unwanted materials present in the cell.

• Endoplasmic reticulum plays an important role within the internal organization of the cell by synthesizing selective molecules and processing, directing and putting them to their appropriate locations.

Types of Cells

Cells are similar to factories in which different departments work together to achieve a common goal. Different types of cells perform various functions. There are two types of cells based on cell structure.

1. These cells have no cells. Some cells such as bacteria have free-floating or suspended genetic material in the cell space known as nucleoids.

2. Prokaryotic cells are found in single-celled organisms like bacteria, archaea, cyanobacteria, etc.

3. The size of the cell ranges from 0.1 micrometres to 0.5 micrometres in diameter.

4. Their hereditary or genetic material can either be RNA or DNA.

5. Single-celled organisms reproduce through asexual reproduction such as binary fission. They use conjugation, a form of reproduction that appears to be sexual but it’s not.

1. Eukaryotic cells have a true nucleus.

2. Their cell size ranges from 10 to 100 micrometres in diameter.

3. Eukaryotic cells are found in organisms like fungi, plants, animals and protozoans.

4. The plasma membrane manages the transportation of nutrients in and out of the cell. It is also accountable for establishing cell to cell communication.

5. They reproduce through both methods of reproduction, asexual and sexual.

6. In eukaryotic cells, we can see some contrasting characteristics between animal and plant cells. For example, plant cells have cell walls, chloroplasts, plastids and central vacuoles but animal cells don’t have these organelles.

Cell Organelles

Cells consist of cell organelles that perform specific functions to carry out important life processes. Here are different cell organelles with their functions. 

• Nucleolus– It is the site of ribosome production. It controls cellular activities and reproduction.

• Nuclear Membrane– It protects the nucleus from getting mixed with other cell organelles.

• Chromosomes– It is a major factor that determines the sex of an individual. There are 23 pairs of chromosomes in each human cell.

• Endoplasmic Reticulum– It is responsible for transporting substances throughout the cells. It helps in the metabolism of carbohydrates and the synthesis of steroids, proteins and lipids.

• Golgi Bodies– These organelles are called the post office of the cells as they are involved in the transportation of materials within the cells.

• Ribosomes– They help in protein synthesis.

• Mitochondria– These are known as the powerhouse of the cell as they help to generate energy.

• Lysosomes– They destroy the foreign particles immigrating to the cells by engulfing them. Therefore, they are known as suicidal bags of the cell.

• Chloroplasts– These are involved in photosynthesis.

• Vacuoles– They store water, nutrients and other waste materials in the cell. 

What are the Different Functions of a Cell?

A cell performs these major functions which are essential for the growth and development of an organism. Some of the vital functions of a cell are :

• To Provide Support and Structure to the Cell – All organisms consist of cells. They form the building blocks of all organisms. The cell wall and the cell membrane are the two main organelles whose function is to provide strength and support to the organism. For example, skin is built of a large number of cells, xylem is a vascular tissue in plants that is made up of cells that provides strength and support to the plant. 

• To Facilitate the Growth Mitosis –  Mitosis is a process of cell growth in which the parent cell divides to form two daughter cells. Through this method, cells multiply and facilitate the growth and development of an organism. 

• To allow the Transport of Nutrients –  Cells accept various nutrients inside them for carrying out different metabolic functions. During these processes, the waste is discarded by the cells through passive and active transport. Small molecules like carbon dioxide, oxygen and ethanol diffuse through the cell membrane along the concentration gradient. This process is known as passive transport. However, the larger molecules are transported through active transport in which the cell requires a lot of energy to carry out the process. 

• To Aid in Reproduction –  A cell undergoes the process of reproduction through mitosis and meiosis. Mitosis is also known as asexual reproduction in which the parent cell divides to form daughter cells. However, in meiosis, the two daughter cells are genetically different from their parent’s cells. Therefore, we can comprehend why cells are called functional and structural units of life. This is because they provide strength, support and stability to the organisms and perform different functions important for undergoing life processes. 

• To help in Energy Production – Cells need energy to perform important activities. This energy is generated by cells through a process called respiration in animals and photosynthesis in plants.