Enzymes Flashcards
What is a catalysis?
Study of how fast chemical reactions proceed
What is a catalyst?
A substance that increases the rate of chemical reactions
How do catalysts act?
By reducing the activation energy of a chemical reaction
What are enzymes?
Proteins which are biochemical catalysts
Relative specificity
Acting on several structurally related substances
Absolute specificity
Acting on one and only one substance
Stereochemical specificity
Acting on a specific stereoisomer
What can be regulated?
The catalytic behavior of an enzyme
What are coenzymes?
Organic molecules that act as cofactors
What are cofactors
Small organic molecules and ions (Zn, Co, Fe)
When can enzymes be catalytically active?
Only if a specific group or cofactors is attached to them
What makes an active enzyme?
Apoenzyme and cofactor (coenzyme or ion)
What is an active site?
Location on an enzyme where a substrate is bound to initiate catalysis
When does a binding of a substrate to the active site occur?
By matching intermolecular forces
What happens when an enzyme binds to a substrate?
Is forms an enzyme-substrate complex which releases a product
What is the lock-and-key model?
When the rigid enzyme and substrate have matching shapes.
Active site + substrate= EXACT FIT
What is the induced-fit model?
When the flexible enzyme changes shape to match the substrate.
Active site ADJUSTS to fit substrate
What is the enzyme activity?
The rate at which an enzyme catalyzes a reaction.
=speed
What is the turnover number?
The number of molecules of substrate acted on by one molecule of enzyme per minute.
=the amount
What factors affecting enzyme activity are due to kinetics ?
Enzyme and substrate concentration
What factors affecting enzyme activity are affecting the structure of an enzyme?
Temperature and pH
Enzyme concentration
Increase the number of enzyme
Substrate concentration
Increase substrate, reach max velocity
What happens when you increase temperature?
denaturation
What is an ezyme inhibitor?
A substance that decreases the rate of an enzyme-catalyzed reaction.
What is an irreversible inhibition?
Forms. Strong bond with a specific functional group of an enzyme rendering it inactive.
(Kills enzymes)
Reversible inhibition
Competitive and in competitive inhibitor
Competitive inhibitor
Substrate + inhibitor takes the same spot in the enzyme.
How to restore the activity of the enzyme?
By adding more substrate
Noncompetitive inhibitor
- Binds to the enzyme at a location other than the active site
- cannot be reversed by adding more substrate
- often changes the active site of the enzyme
Activation of zymogens (proenzymes)
Inactive precursor of an enzyme
Why are enzymes released in an inactive form?
To become fully active only when needed
What happens when enzymes perform functions if they were released in an active form?
It could degrade cell components
Allosteric regulation
Uses allosteric enzyme and modulator
Allosteric enzyme
An enzyme whose activity is changed by the binding of modulators
What is a modulator
A substance that binds to an enzyme at a location other than the active site and alters it’s catalytic activity.
Example of Allosteric regulation
Final product becomes a noncompetitive inhibitor of an early enzyme in the pathway for biosynthesis of isoleucine.
Genetic control
The synthesis of proteins is under genetic control
Example of genetic control
Enzyme induction : synthesis of enzymes in response to a temporary need of the cell
When cells are damaged or die, what do enzymes do?
Reside inside the cells and are released
How to detect a condition in the concentration of enzymes in blood?
If level goes up. Usually, the level remains low
Isoenzymes
Slightly different form of the same enzyme produced by different tissues (ex: LDH)
What is used in the diagnosis of a wide range of diseases!
Serum levels of LDH due to the difference in tissue distribution of LDH isoenzymes.
Alkaline phosphate (ALP)
Liver or bone disease
Amylase
Pancreas disease
Creatinine phosphokinase
Heart attack
Aspartate transaminase (AST)
Liver and/or heart attack
Alanine transaminase (ALT)
Hepatitis
Lactate dehydrogenase (LDH) l
Liver and/or heart attack
Lipase
Acute pancreatitis
Lysozyme
Monocytic leukemia
