Chapter 4

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Fin R.

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Enzymes  
Protein catalysts that increase the rate of reactions
Ribozymes 
RNA demonstrates enzymatic activity
Role of Ribozymes
Remodeling RNA molecules, formation of polypeptide in ribosomes
Do catalysts change at the end of a reaction?
No
Activation Energy 
Amount of energy required for reaction to proceed
Substrate 
Molecules that combine with active sites of enzyme, have specific shapes
Isoenzymes 
Enzymes produced by different organs that catalyze the same reaction but differ in amino acid composition
Enzymatic Activity Influences 
Temperature, pH, cofactors, coenzymes, substrate and enzyme concentration, stimulatory and inhibitory effects of products
Cofactors 
Substance needed for catalytic action of enzyme (inorganic ions)
Coenzymes 
Organic molecule derived from water-soluble vitamin that combines with and activates enzyme proteins
Zymogens 
Inactive digestive enzymes that are activated after they are secreted into intestine
Metabolic Pathways 
A sequence of enzymatic reactions that begins with substrate, progresses through intermediates, and ends with final product
End-product Inhibition 
Inhibition of enzymatic steps by products (negative feedback)
Allosteric Inhibition 
Alteration of enzymatic activity by combination with regulator (negative feedback)
Inborn Errors of Metabolism 
Quantity of intermediates formed prior to defective enzymatic step increases, quantity of intermediates and final products formed after defective step decreases
Bioenergetics 
Flow of energy in living systems
Endergonic Reactions 
Require input of energy from external source
Exergonic Reactions 
Reactions that liberate energy
ATP Formation 
ADP and Pi
Coupled Reactions 
Oxidation-Reduction
Reduced 
Gains electrons
Oxidized 
Loses electrons
Reducing Agent 
Donates electrons
Oxidizing Agent 
Accepts electrons
NAD 
Derived from niacin (B3)
FAD 
Derived from riboflavin (B2)
Involved in transfer of hydrogen atoms
NAD and FAD