An Amazing Journey through DNA Replication

Prologue: 

In this prologue, the cell replicates it's DNA inside the nucleolus. As the cell grows bigger, it needs more nutrients and space in order to survive. Before undergoing mitosis, DNA replication has to happen first.

ACT 1: Initiation 

An enzyme called Helicase, unwinds the double helix DNA molecule and separates the strands; this also breaks the hydrogen bonding between nitrogenous bases. SSBP (Single-strand binding proteins) stabilize the DNA strands and this creates replication bubbles. As tension builds up during the unwinding, DNA Gyrase enzymes cuts the DNA in order to release the tension. RNA Primase enzymes place RNA Primers to signal Polymerase III to begin replicating the strands.

ACT 2: Elongation 

DNA Polymerase III synthesizes the new DNA from a 5' to 3' direction and adds free nucleotides to the 3' direction. Since DNA is an anti parallel structure, the two new strands will have to grow in an opposite direction. A new strand of DNA called "the leading strand" replicates continuously using a 3' to 5' so that it will become 5' to 3' with the template. Another new strand of DNA is called "the lagging strand" replicates discontinuously as RNA Primase comes in and synthesizes a short RNA Primer, which will be extended by DNA polymerase III to form sections called Okazaki Fragments; the leading strand replicates in an opposite direction with the lagging strand.

Act 3: Termination

DNA Lygase enzyme acts as a glue and joins each Okazaki fragment together. Phosphodiester bonds are created between DNA Lygase and Okazaki fragments. DNA Polymerase I comes in and proofreads the newly synthesized strands and replaces the RNA Primer with DNA. At last the two new DNA molecules separate from each other.
DNA Replication is now complete!

The Relationships between Catabolism, Anabolism and Metabolism

The Definition of Catabolism:

The metabolic breakdown of complex molecules into simpler ones, often resulting in a release of energy. 

Examples of Catabolism:

Glycolysis

Kreb's Cycle

Electron Transport Chain

The Definition of Anabolism:

The phase of metabolism in which simple substances are synthesized into the complex materials of living tissue

Examples of Anabolism:

Calvin Cycle

Cyclic Photosynthesis

Non-Cyclic Photosynthesis
















The Definition of Metabolism:

The total chemical reaction processes that occur within a living organism in order to maintain life

Catabolism + Anabolism = Metabolism

STORY TIME - The Extinction of Passenger Pigeons

             Pigeons, they are everywhere. If you take a walk in downtown Toronto you will most likely see a couple within the block, these animals live wherever they want. There are several species of these pigeons, and today we shall talk about the passenger pigeon.
     
             The name of "passenger" pigeons is refereed as a French word "passager" which means passing by. During the 19th century, these birds were THE MOST abundant bird in North America, possibly even the world. They migrate in huge flocks that have over 3.5 billion birds, it could even blacken the sky! If accurate, that number would be representing a large faction of the entire population at it's time.

             The Government at that period of time had decided to hunt down these birds and pigeon meat were used as cheat food for slaves and the poor. There had been ZERO worries concerning the population of the passenger pigeon as you could literally shoot one down if you randomly aim at the sky. These birds are one of the most sociable birds of all times, without a large flock, they wouldn't be able to communicate with each other. Their diet consists of all kinds of nuts such as acorn and chestnuts, sometimes even berries.

             As the years go on with the constant hunting and commercial exploitation of passenger pigeon meat at a massive scale, the population of these birds start to decline; moreover, deforestation increased rapidly during the 1900s, the bird's habitat had reached to a certain size where there is not enough space for the passenger birds to migrate and reproduce. Conversationalists set up bills that it became illegal to net pigeons within two miles, but this was weakly enforced.

             By the mid-1990s, the passenger pigeon total population almost completely disappeared. At last there were only 1 passenger pigeon left in the entire world, it's name was Martha. She was kept in Cincinnati Zoo and was named as the loneliest bird ever; she died in September 1st, 1914. This was the end of the most abundant bird in the world. This year - 2014 is the 100th anniversary of remembrance of the passenger bird.

             After hearing this story told by our tour-guide, I felt extremely depressed as to know that humans have the power to wipe out a species that was abundant. Who knows which abundant species would go extinct next with all these global warming and loss of animal habitat from deforestation. This story needs to be heard by a lot more people, as far as i know; most people don't even know about the passenger bird's legacy.