1A - Enzyme Structure and Function (Bio, BC)

Question 1

How are enzymes typically named?

Answer 1

Enzyme nomenclature tends to be based of their function, following “ase” as the suffix.
In total, there are ~8 classes you need to know for the MCAT

Question 2

What are the 8 different classes of enzymes?

Answer 2

Oxidoreductase, Transferases, Hydrolases, Lyases, Isomerases, Ligases, Translocases, and Phosphorylases
Mnemonic: Over The HILL: Oxidoreductase, Transferase, Hydrolases, Isomerases, Lyase, Ligase (don’t forget translocase and Phosphorylases)

Question 3

Compare and contrast Transferases and Translocases.

Answer 3

Transferases - these types of enzymes move functional groups from one place to another
Translocases - these enzymes catalyze the reaction of ions or molecules moving across a membrane or separating from a membrane (Ex: seen in secretion systems in gram + bacteria)

Question 4

Contrast ligases from lyases

Answer 4

Ligase - “ligate” 2 molecules into one

Lyases - “lyse” one molecule into 2

Question 5

Contrast hydrolases from lyases

Answer 5

Hydrolases - these require the use of water to break covalent bonds of a molecule
Meanwhile, lyases are able to promote the elimination of a group without water

Question 6

In text you read, the author states, lyases have the ability to catalyse reverse reactions. Are they right?

Answer 6

Yes! Most reactions in chemistry is notable in combining 2 molecules to produce one. Therefore, in reversing the reaction, the one molecule splits into 2. This is the only occasion in which lyases can be used in this manner however.

Question 7

Dehydrogenase is an example of what class of enzymes?

Answer 7

An oxidoreductase! These have the ability to catalyze redox reactions and dehydrogenases are notorious in helping transfers electrons; Ex: In cellular respiration

Question 8

A mutase rearranges a molecule by transferring a phosphate. What type of enzyme is this?

Answer 8

While it does use a Pi, this enzyme is in fact an isomerase because its main role is to rearrange. Mutases moves specifically the functional group - Pi - to a new location within the SAME molecule. This means the new molecule is simply and isomer of the old one.

Question 9

A Kinase is what type of enzyme?

Answer 9

A kinase is a transferase. Enzymes of this class transfers functional groups to DIFFERENT molecules

Question 10

What does a phosphatase and protease have in common?

Answer 10

Both are hydrolases, meaning they use water in order to break covalent bonds.
Phosphatases - uses water to convert GTP -> GDP
Proteases - these are enzymes that use water to break down protein; seen in GI and digestion.

Question 11

Does phosphorylases and kinases use water to complete their functions?

Answer 11

No! Both are transferases! This means they transfer functional groups from one molecule to the next without the role of water