Translation is the process in which mRNA is decoded to build long chains of amino acids, these chains are commonly referred as proteins or polypeptides chains. This process occurs in three stages within a cells ribosomes, the stages are named; initiation, elongation, and termination. In initiation, a ribosome divides into 2 subunits; one smaller and the other larger, an initiator tRNA carrying the amino acid methionine binds to the 5’ end of the mRNA molecule with the help of the smaller ribosomal subunit, together they move in the 3’ direction until they reach the start codon AUG. The larger subunit then joins the mRNA molecule to form the initiation complex, the combined ribosome provides a set of slots known as the A, P, and E sites. These slots allow tRNA anticodons carrying amino acids to bind to matching mRNA codons on the mRNA template molecule. With the initiation complex formed elongation is initiated, the polypeptide chain starts at the initiator tRNA in the middle slot of the ribosome called the P site. The A site is slightly ahead of the P site and is where the next tRNA anticodon will land. Once the new tRNA has landed at the A site, the methionine from the initiator tRNA in the P site is transferred onto the amino acid of the tRNA in the A site to form a peptide bond; officially creating a small polypeptide chain. The polypeptide chain is pulled backwards in the 5’ direction so the empty tRNA can be released through the E site slightly behind the P site exposing a new mRNA codon at the A site. This cycle continues until termination is initiated by a stop codon such as UAG, UAA, OR UGA entering the A site. Release factors are triggered to enter the P site and add a water molecule to the last amino acid of the polypeptide chain, this allows the chain to separate from the tRNA. The released protein will fold into a distinct 3D structure and/or can join with other proteins to form a multi-part protein, special amino acid sequences in the polypeptide chain determine where the newly synthesized protein will go. The cellular process of translation allows genetic information to take a physical form, without this ability life simply could not exists.

References:

https://www.khanacademy.org/science/biology/gene-expression-central-dogma/translation-polypeptides/a/translation-overview

Transcription is the first step in gene expression and initiates the central dogma of molecular biology. Transcription is the process in which DNA sequences are transcribed to make RNA molecules over 3 steps; initiation, elongation, and termination. The process is initiated by RNA polymerase binding to a promotor; a specified sequence of DNA nucleotides. Once bound to a promotor RNA polymerase separates the two DNA strands. Once the two strands of DNA are separated elongation occurs, one strand acts as a template for RNA polymerase to build complimentary RNA nucleotides one base at a time. As RNA polymerase reads the DNA template, forming the RNA molecule, the chain grows from 5’ to 3’. RNA polymerase will continue transcribing until it reaches a specific group of nucleotides forming a terminator, this causes the entire process to end and is known as termination. The RNA molecule is then processed to make messenger RNA or mRNA, this molecule will go on to be translated into a protein.

References:

https://www.khanacademy.org/science/biology/gene-expression-central-dogma/transcription-of-dna-into-rna/a/stages-of-transcription

​In the early 1900’s the scientific field of molecular biology was a complete mystery to scientists, the name molecular biology wasn’t even coined until the year 1938 by Warren Weaver. Scientists at the time had no explanation for how genetic information dictated the formation of proteins in a biological system or even which biological molecule contained the genetic information. Francis Crick and James Watson were two scientists who were fixated on answering these questions. By the year 1953, they discovered that genetic information was encoded by DNA in a double helical structure. Shortly after, in 1957 they presented the relationship between DNA, RNA, and proteins called “the central dogma of molecular biology”. This explained how genetic information in the form of nucleotide sequences in DNA are transcribed into RNA to be later be translated into functional proteins. This discovery was a major breakthrough in molecular biology and allowed the field to progress heavily.

References:

http://sandwalk.blogspot.com/2007/01/central-dogma-of-molecular-biology.html

The plasma membrane encasing cells is selectively permeable, it controls which substances enter and exit the cell through many processes. These processes can be active or passive requiring a “fuel” such as ATP or can occur without any assistance. One means of transporting molecules across the membrane is by using the electrochemical gradients formed by the plasma membrane. An electrochemical gradient is formed when the charge and chemical concentration is different within and out of the cell. This allows the cell membrane to piggy back much needed molecules on ions such as Potassium or Sodium into and out of the cell. Using this gradient is a passive process which means no energy is required but if a molecule wants to move against the gradient energy is required. In this active process, ATP is consumed to move the molecules against the gradient. The electrochemical gradients allow cells to regulate the transport of molecules efficiently and accurately, this is just one of the means of transport a cell membrane uses to maintain normal processes.

References:

https://www.boundless.com/biology/textbooks/boundless-biology-textbook/structure-and-function-of-plasma-membranes-5/active-transport-66/electrochemical-gradient-336-11473/

Proteins are one of the most influential macromolecules, and almost all aspects of life involve their use. Proteins are able to carry out specified cellular functions; some catalyze chemical reactions needed to maintain life while others are used for signaling or to coordinate internal cell activities or inter-cellular communication. Proteins are able to form large organic molecules because they are polymers, which are large molecules made up of repeated subunits. Proteins form these linear polymers by combining 20 different amino acids, each with unique chemical characteristics.

The sequences of these amino acids that make up the protein are stored in the DNA  located in the nucleus. The DNA is transcribed into RNA, and translated into proteins. The sequence of bases in RNA determines the order of successive amino acids that will result in new proteins. The formation of proteins occur within the ribosomes, which are large complexes of RNA and protein molecules. The sequence of amino acids in a protein is known as the primary structure that determine how the protein will fold. The interactions between those primary structures form local secondary structures, when the secondary structures interact they form the overall three-dimensional shape or its tertiary structure. These tertiary structures are called polypeptides, some proteins are a combination of these polypeptides forming quaternary structures.

These macromolecules play a vital role in immune defense, energy storage, and structure creation. They can also be used as enzymes to catalyze or speed up chemical reactions. Each enzyme recognizes one or more substrates to catabolize, synthesize, or rearrange their substrates. They can also send messages within cells and across the body. Examples include hormones such as insulin and glucagon that coordinate different body systems. Furthermore, they transport oxygen across the body through hemoglobin. Proteins allow for the wide range functions of life to maintain homeostasis and can become infinitely complex and add to life’s diversity.

Atoms can combine together to form molecules, and chemical bonds are the different forms of attraction between these atoms. The most common forms of chemical bonds are ionic, covalent, and hydrogen bonds. Each chemical bond has its unique attributes that make them strong or weak in a range of situations. Ionic bonds form between ions with opposite charges as electrons are transferred from one atom to another creating a strong bond. An example would a positively charged sodium ion attracted to a negatively charged chloride ion, making sodium chloride. Covalent bonds form between. Non-metal atoms when the electrons in outermost valence shells are shared. They form when hydrogen and chlorine ions combine to form hydrogen chlorideCovalent bonds can be polar or nonpolar. In polar covalent bonds, electrons are unequally shared by the involved atoms, causing slightly positive and slightly negative charges to form in different parts of the molecule. A polar covalent bond example would be the bonding of Hydrogen and oxygen between water molecules. Nonpolar covalent bonds form between two atoms of the same element or atoms that share electrons equally.

Finally, hydrogen bonds occur between a hydrogen atom with a slight positive charge and an electronegative atom of another molecule. Hydrogen bonds are much weaker than ionic or covalent bonds, but become much stronger as many hydrogen bonds form together. Hydrogen bonds give water its unique properties to support life, such as cohesion and adhesion. To summarize, chemical bonds Give atoms the ability to combine into more complicated and diverse structures that make up all known organic and inorganic molecules throughout the cosmos.

Taxonomy is the science of describing, naming, and classifying all living organisms. Taxonomists use genetics alongside behavioral and physical observations to classify all plants, animals, and microorganisms into specific classifications. Taxonomists have so far classified close to 2 million plants, animals, and microorganisms but an estimated 5 to 30 million different species exists on earth. As organisms become more loosely related they progress up an order until the 3 domains of life.  A species is the lowest level in taxonomy, they are classified as a group of organisms that have the capability to breed with one another.  As multiple species become loosely related they are classified as a genus. This trend progresses up a latter from species, genus, family, order, class, phylum, until the 3 domains of life.

The 3 domains of life are Eukaryota, Bacteria, and Archaea. Each domain has specific attributes with Eukaryotes composing life that most people see in their day to day activities. All animals, plants, fungi, and protists are in this domain, they have eukaryotic cells with membranes composed of unbranched fatty acid chains attached to glycerol by ester linkages and contain rRNA that is unique to this domain. Bacteria are prokaryotic cells that are similar to eukaryotes cells but contain no nucleus, lack membrane-bound organelles, and their own unique rRNA. Finally, the domain Archaea is composed of single-celled microorganisms more closely related to eukaryotes over bacteria. Archaean’s inhabit the extreme environments on earth such as deep sea rift vents and extremely alkaline or acid waters.