What is a substance that speeds up the rate of a chemical reaction called?

A substance which speeds up the rate of a chemical reaction is called as catalyst. A catalyst enhances the rate of the reaction without itself being utilized in the reaction. A catalyst do so by lowering the activation energy.

A catalyst provides an alternate pathway which requires lower activation energy for the reaction to proceed and form reaction products.

Metals like Nickel (Ni), Iron (Fe) etc are some examples of catalysts.

In biochemical reactions, enzymes do the same work as that of catalysts with the only difference that enzymes can be regulated but catalysts can't be regulated.

Best example of enzyme is catalase.

you are certainly talking about this picture:

a: is the label of the white square, it is showing the  replication fork, formed by helicase (d) ==> so it is the site of dna separation and replication 

b: is a new dna brand that is following directly the replication fork, so it is continuous ==> built continuously from 5' to 3

c: dna polymerase cannot replicate dna on its own, it needs the of their proteins, and one of them plays the role of a clamp which fixes  the dna with the dna template and increases  the processivity of the enzyme. ==>   stops polymerase from falling off the  template.

d: is the enzyme responsible for forming the replication fork (helicase) ==> unwinds and separates dna into two strands

e: is the delayed strand, it is built  in the opposite sense of the helicase, so dna will be built in fragments ==> built  fragments from 5' to 3 joins

and finally f: is the enzyme that builds  the new dna strand (dna polymerase) ==>   adds nucleotides to make a new dna helix.

credit: gradman555p98x9p

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igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.