The biotechnology industry is fully dependent on living organisms. The cell being the basic unit, living organism consists of one or multiple cells and some organisms are unicellular like bacteria and yeast. Humans are multi cellular having trillions of cells. All cells have a common mode of survival, and Biotechnology combines these modalities to manufacture drug to treat diseases and improve health. In order to comprehend the cell process specific input in detailed functioning of the cell is required.

  • Cells Reproduce (mitosis): Before it divides, a cell makes a copy of the DNA and the other cell parts. From the original cell it forms two identical cells and these are referred to as the daughter cells. These cells then grow to their intended size.
  • Cells Metabolize: This is a process by which cells maintains a living state by harnessing nutrients, break down into large and small molecules, produce energy by building molecular blocks, which in turn are used to create new cell structures and control cellular function.
  • Cells Respond to stimuli: Unicellular and multicellular organisms respond to a whole range of stimuli both internal and external. For instance plants grow towards the source of light for photosynthesis and in order to produce energy. This response is essential for its survival. Cells can also adapt since organism may thrive or die according to their adaptability in adverse environmental conditions like, change in temperature, solute concentration, oxygen supply and exposure to hazardous agents.

Parts of an Animal Cell

This can be divided into three broad sections like the cell membrane the cytoplasm (includes organelles) and the nucleus.

Nucleus:  Contains most of the DNA and functions as the control center of the cell. It is encompassed by a membrane that releases molecules in and out of the nucleus in order to safeguard the DNA. The DNA does not ever leave the nucleus.

Cell Membrane:

The surrounding border of a cell is the cell membrane which control the inflow and outflow of the cell. Inside the cell membrane are receptors which act as storage facility for molecules. When a specific type of molecules enters a receptor, chemical reaction takes place which in turn creates a cellular response. Blockage in a receptor evokes no response since signaling is not present. This is how biologic therapy works. They attach to receptors and interrupt the cell signaling process or others by invoking the signaling molecule.

Organelles:

There are various types of organelles inside the cytoplasm of a cell performing multiple of functions. Ribosomes makes protein, Mitochondria produces energy. By a mechanism of folding endoplasmic reticulum and transport specific proteins, golgi bodies help to modify proteins for transportation within the cell. Vacuoles store cellular wastage for disposal.

Within one minute Ribosomes can assemble an average size protein

DNA

All cells contain deoxyribonucleic acid or DNA and thereby it is the foremost factor in cell construction and operation. It (DNA) is constructed in sections called Chromosomes within which are specific parts of DNA called genes. Genes vary in length, and stores information that a cell needs to manufacture proteins which in turn impacts cellular functions.

Note: [In animal cells, Mitochondria are the only organelles to have their own DNA. Mutations or divisions in Mitochondria DNA leads to diseases like Kearns-Sayre syndrome causing loss of heart, eye and muscle movement functions]

The DNA consist of four basic “Building Blocks” called nucleotides and is a code storing information. The length of DNA is very long and the order of the nucleotides dictates the information stored. Three distinct components constitutes the nucleotide namely a deoxyribose, sugar, a phosphate group and a base. There are four types of bases: adenine (A), thymine (T), guanine (G) and cytosine (C). The basic sequence of As, Ts, Cs, and Gs in DNA imparts meaning to the cell, similar to alphabets in a word imparts meaning to it, or even in a story in which the word appears. The diverse nature of organisms is a result of a unlimited combination of bases- As, Ts, Gs and Cs. Although every organism contain DNA but, the arrangement and number of bases vary for each organism.

DNA is referred to as double helix because two strands of nucleotides bond together in a very exact manner. For instance, As bond within Ts, Cs bond with Gs, resulting in A.T and C-G combinations. These are called base pairs. In every human cells, the length of DNA is equivalent to 3 billion base pairs. If the structure of DNA is flattened, it would resemble a ladder with two side rails (phosphate and ribose groups) and rungs (base pairs) between them. This enables DNA to be very stable and store vast amounts of information.

Humans have 23+ 23=46 pairs of chromosomes, half from each parent, and Chromosomal abnormalities can be numeric or structural

Most cells in an organism contains the exact same DNA, but not all genes are always active or turned on, But whenever a gene is turned on, the encoded information helps to produce or express, the enclosed protein. When not active or turned on it cannot express proteins. Therefore depending on the need of the cell function, genes become active or inactive. Many diseases are a result of this impropriety.

Mutations:

A change in the DNA sequence is called mutation and is basically a result of environmental factors like exposure to radiation or chemical toxins. Mutations can also be a result of natural process of DNA replication, wherein a cell is copying 3 billion base pairs in 20 hours. Bases can be substituted, deleted or repeated and this change in DNA sequence may cause in harboring dysfunctional proteins or just the opposite. Accumulation of mutation over a period of time in genes can result in differences in species.

Genomes:

This is a term which refers to all genetic information in an organism. The human genome is the entire DNA content found in a human. Genomes are made up of the same bases: As, Ts, Gs and Cs. The difference lie in the sequence and numbers of base pairs and genes. The numbers of base pairs does not correspond to the number of genes and hence the two are independent of each other. Human genome has 3 billion base pairs and approximately 20,000 to 25,000 codes for genes. Only 3 percent of human genome codes for genes, 97 percent are noncoding DNA or in other words do not have instructions for creating proteins. Biologists are yet to discover this strange phenomenon but concur that it may be due to evolution in species or regulatory functions within the cell.

Note: [Variation in individual nucleotides occur at the rate of one in every 13,000 base pairs in most organisms. In humans it is one in every 1200. However, most of these mutations do not adversely affect us and only a few causes dysfunctional protein or diseases status]

It is to be noted that the number of base pairs and genes have no relevance to the intelligence or physical capability of an organism. An amoeba genome is a unicellular organism which has 670 billion base pairs compared to 3 billion in a human genome. Yet the human is more complex, intelligent and physically capable organism.

Proteins:

These are along chains of amino acids that fold into intricate and complex 3-D shapes. In a gene the DNA sequences determines the order of amino acids and their sequence determines the shape and functions of the protein. The highest number of genes in an organism is 60,000 for the bacteria that causes trichomoniasis, three times as many as in a human genome.

Transcription and Translation are two complicated and multiple steps in protein synthesis.

Transcription:

During this process the original DNA code is rewritten into a molecule called messenger RNA (mRNA). mRNA consists of nucleotides that are slightly different from DNA nucleotides. RNA molecules are similar to DNA but contain ribose sugar of single strand and use all U or uracil, in place of T, or thymine as one of the four possible bases.

Translation:

During translation ribosomes help to assemble individual amino acids into proteins and also bind to mRNA. Three mRNA nucleotides constitute a Codon which is the code for an amino acid. In the process of translation, transfer RNA (tRNA) decodes mRNA and attaches to the corresponding amino acid. Therefore a specific combination of amino acids are linked together as required by the sequence of nucleotides on the mRNA.

Short chains of amino acids are called peptides and the long one is polypeptide which fold into a functional protein. Numerous types of protein perform various functions within and between cells. Proteins called enzymes bind or break molecules. Signaling molecule transmit messages from one to another, as also protein receptors which receive signals through a communication channel known as Signal Transduction. Some proteins move substances out of a cell whilst structural proteins impart shape to cells and organism. Proteins are involved in cellular recognition and identification, while others such as antibodies help in defense of organism against diseases.