Enzymes Essential Question: How do enzymes work and what is their role in DNA replication?

What is an enzyme? Enzyme: A protein that decreased the activation energy needed for a reaction to start

How do enzymes lower the activation energy? Enzymes bind with the reactions in a chemical reaction (these are called the “substrate”). Each type of enzyme can only bind with one specific substrate. The place where the enzyme and the substrate meet is called the activation site. LET’S PLAY THE ENZYME-SUBSTRATE GAME!!!!

What can affect the enzyme’s ability to bind with the substrate? pH Temperature Changes in either pH or temperature can change the enzyme’s structure, making it unable to do its function quickly or at all!

DNA Replication When DNA replicates prior to cell division, it gets help from enzymes. Each enzyme does a specific job that must be completed before DNA replication can move from one step to the other. All of the enzymes on the next slide are important players in DNA replication. They also all end in “-ase,” a good indication that something is an enzyme!

Helicase To start DNA replication, the DNA strand has to “unzip” or break into two sides. HELICASE is the enzyme responsible for this part of DNA replication. It “unzips” the DNA.

DNA Polymerase Next, a special enzyme rebuilds the DNA from its two separate strands. DNA POLYMERASE is the enzyme responsible for this part of DNA replication. It rebuilds the two new DNA strands using the nitrogenous bases left behind on either side (A with T, C with G).

Primase When DNA gets rebuilt, it has to be rebuilt in the perfect order – from one side of the DNA molecule to the other PRIMASE lead the DNA Polymerase along the DNA strand by making a chemical primer (RNA)

Ligase Once the DNA Polymerase has passed over and replaced the correct nitrogenous bases, another enzyme has to bind them together. LIGASE is the enzyme responsible for binding the new nitrogenous bases together on either side of the new DNA strands.