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Study Notes

Enzymes are biological catalysts that speed up the rate of biochemical reactions.
Most enzymes are 3-D globular proteins.
Some special RNA molecules also act as enzymes, called ribozymes.

Active site: A region that binds substrates, cofactors, and prosthetic groups. It contains residues that help hold the substrate in place. This shape is determined by the tertiary structure of the protein.
The active site is divided into two parts:
- Binding site: This part of the active site recognizes and binds the substrate.
- Catalytic site: This part of the active site performs the catalytic action of the enzyme.
Cofactors: Non-protein molecules that carry out chemical reactions that cannot be performed by the standard 20 amino acids; they activate the protein.
Apoenzyme: an enzyme without its cofactor.
Holoenzyme: a complete enzyme comprising the apoenzyme and its cofactor.

Inorganic cofactors: Inorganic molecules needed for proper enzyme activity.
Example: Magnesium (Mg) is a cofactor for hexokinase.
Organic cofactors: Organic molecules needed for proper enzyme activity.
- Prosthetic groups: Tightly bound organic cofactors.
- Examples: Flavins, heme groups, biotins.
- Coenzymes: Loosely bound organic cofactors.
- Examples: NAD+, FAD.

Enzyme kinetics: The branch of study that examines the rate of enzyme-catalysed reactions.

Inhibition: Prevention of enzyme activity via interactions with inhibitors.
Reversible inhibition: Inhibitors can bind and unbind from the enzyme.
- Competitive inhibition: Inhibitors compete with the substrate for the active site.
- Non-competitive inhibition: Inhibitors bind to a site other than the active site (allosteric site).
- Mixed inhibition: Inhibitors can bind to either the enzyme or the enzyme-substrate complex.
Irreversible inhibition: Inhibitors bind to an enzyme permanently, halting its activity.
Examples: Aspirin, which targets and covalently modifies a key enzyme involved in inflammation.

Activation: Conversion of inactive enzyme form to active form.
Cofactors: Enzymes can be activated by cofactors which are non-protein molecules that assist in aiding certain reactions.
Zymogen Activation: Inactive enzyme precursors are activated via proteolytic cleavage.

Bond specificity: Enzymes act on substrates with a similar structure and containing a particular bond type.
Group Specificity: Enzymes are specific to the structure surrounding the substrate.
Substrate Specificity: Enzymes only act on a particular substrate.
Optical/Stereo-specificity: Enzymes exhibit specificity towards an optical configuration.
Dual Specificity: Enzymes act on a single substrate through two different types of reactions.

Lipids are diverse groups of chemical compounds including fats and oils.
They are hydrophobic and some are amphipathic (possessing both polar and non-polar parts).

Carbohydrates are polyhydroxyaldehydes or polyhydroxyketones that yield simpler sugars upon hydrolysis.
Carbohydrates have general formula: C_n(H₂O)_n.
There are three main classes of carbohydrates:
- Monosaccharides: Simplest carbohydrates that cannot be hydrolysed.
  - Aldoses: Contain aldehyde groups.
  - Ketoses: Contain ketone groups.
- Disaccharides: Two monosaccharides linked by glycosidic bond.
- Polysaccharides: Multiple monosaccharides linked together.
- Examples: Glucose, fructose, sucrose, cellulose.

Nucleic acids are biopolymers containing monomer units:
- Bases (purines and pyrimidines)
- Monosaccharides (pentoses)
- Phosphate Groups
The primary structure of a nucleic acid is the sequence of bases.
Secondary structure involves the 3-dimensional conformation of the polynucleotide backbone.
Tertiary structures pertain to the interactions between DNA and proteins.