MCAT Biochemistry
There are six different classes of enzymes (proteins that accelerate chemical reactions). The first class is oxidoreductases, which catalyze oxidation-reduction reactions involving electron transfer between molecules. Next, we have transferases, enzymes that transfer functional groups from one molecule to another. Following that, hydrolases are enzymes that use water to break bonds in a molecule. The fourth class includes lyases, enzymes that break bonds without water. Isomerases make up the penultimate class, involving enzymes that create isomers or rearrangements within molecules without changing the molecular formula. Finally, ligases are enzymes that create bonds between similar molecules.
Now, let's talk about cofactors, the molecules that must be bound to some enzymes for them to function and catalyze reactions. Cofactors can be inorganic metal ions or organic molecules known as coenzymes. An enzyme with all its cofactors bound is called a holoenzyme, while an enzyme without its cofactors is referred to as an apoenzyme. Coenzymes come in two categories: prosthetic groups, which stay permanently attached to enzymes, and cosubstrates, which are temporarily attached during a reaction.
Lesson Outline
<ul> <li>The six different classes of enzymes</li> <ul> <li>Oxidoreductases - catalyze oxidation-reduction reactions involving electron transfer between molecules</li> <li>Transferases - enzymes that transfer functional groups from one molecule to another</li> <li>Hydrolases - enzymes that use water to break bonds in a molecule</li> <li>Lyases - enzymes that break bonds without water</li> <li>Isomerases - enzymes that create isomers or rearrangements within molecules without changing the molecular formula</li> <li>Ligases - enzymes that create bonds between similar molecules</li> </ul> <li>Cofactors</li> <ul> <li>Definition: molecules that must be bound to some enzymes for them to function and catalyze reactions</li> <li>Types of cofactors</li> <ul> <li>Inorganic metal ions</li> <li>Organic molecules known as coenzymes</li> </ul> <li>Holoenzyme - an enzyme with all its cofactors bound</li> <li>Apoenzyme - an enzyme without its cofactors</li> <li>Categories of coenzymes</li> <ul> <li>Prosthetic groups - stay permanently attached to enzymes</li> <li>Cosubstrates - temporarily attached during a reaction</li> </ul> </ul> </ul>
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FAQs
There are six major classes of enzymes, each with specific functions: (1) Oxidoreductases catalyze oxidation-reduction reactions; (2) transferases are involved in transferring functional groups between molecules; (3) hydrolases catalyze the hydrolysis of bonds; (4) lyases participate in the formation or removal of double bonds; (5) isomerases are responsible for isomerization reactions; and 6) ligases join two molecules together.
Cofactors are non-protein chemical compounds or metallic ions that are required for a certain enzyme's activity. They typically bind to the enzyme and help maintain its structural stability, facilitate substrate binding, or participate directly in the chemical reaction. The complete, catalytically active enzyme with its cofactor is called a holoenzyme.
Coenzymes and prosthetic groups are both types of cofactors but they differ in their interactions with the enzyme. Coenzymes are organic molecules (usually derived from vitamins) that bind to the enzyme temporarily and are modified during the catalytic reaction. After the reaction, they are released and can be reused by other enzymes. Prosthetic groups, on the other hand, are permanently bound to the enzyme and help maintain its structure or play a direct role in the enzyme's catalytic reaction.
Transferases are enzymes that catalyze the transfer of specific functional groups, such as phosphate, methyl, or amino groups, from one molecule (the donor) to another (the acceptor). This transfer process is an essential part of many cellular processes, including metabolism, signal transduction, and regulation of gene expression.
Oxidoreductases are enzymes that catalyze oxidation-reduction (redox) reactions, which involve the transfer of electrons between molecules. These enzymes play crucial roles in numerous biological processes, such as energy production through cellular respiration, fatty acid oxidation, and detoxification of foreign substances. Their activities maintain the balance between oxidation and reduction states within the cell, which is vital for proper cell function and survival.
