Unit 3 - Metabolism: Enzymes in Metabolic Processes and Their Functions

Enzyme

Biological catalyst for a specific substrate

Catabolic Reaction

A bigger substrate is broken into smaller products (relasing energy)

Anabolic Reaction

Smaller substrates are built into a bigger product (requires energy)

Active Site

Where substrates bind to enzymes. Shaped specifically for that substrate.

Helicase

Breaks hydrogen bonds between bases, “unwinds DNA” for replication to occur.

DNA Polymerase III

Adds nucleotides complementary to the template strand and is used in DNA proofreading.
If an incorrect base was added, it slows to give time to fix. If it still doesn’t fix, 3’ end moves to a proofreading exonuclease active site to remove the wrong base.

DNA Polymerase I

Removes primers after DNA Polymerase III adds the nucleotides.

Taq DNA Polymerase

DNA Polymerase from bacteria (T. aquaticus) that can withstand high temperatures and is used in PCR

Restriction Endonuclease

Used in Gel Electrophoresis to cut DNA into fragments

Primase

Synthesizes and adds RNA primers to template strands to provide a starting point for DNA Polymerase III.

Ligase

Joins the Okazaki fragments on the lagging strand by forming a phosphodiester bond between the 3’ end of one nucleotide and 5’ end of the next.

RNA Polymerase

Used in transcription to synthesize the mRNA strand.

Spliceosomes

Enzymes that cut out introns from pre-mRNA during post-transcriptional modification.

NOT ENZYME: Proteasome

Large protein complex required to break down unneeded proteins into amino acids through hydrolysis. Amino acids are recycled to synthesize needed proteins.