Enzymes Flashcards
What are endergonic reactions? What will the potential energy graph look like?
- Require energy use by cell (in form of ATP)
- Anabolic
- Products have more potential energy than reactants
- The amount of energy stored in products = the difference in between potential energy in reactants and products
- Photosynthesis, building macromolecules, phosphorylation
- Will not occur without a constant source of energy
What are exergonic reactions? What will the potential energy graph look like?
- Produce energy for use by cell (in form of ATP)
- Catabolic
- Chemical reaction that releases energy
- Reactants whose covalent bonds contain more energy than those in the products
- Amount of energy released = difference in potential energy between reactants and products
- Wood burning, cellular respiration
- Often spontaneous in inorganic substances
What is the relationship between potential energy, stability, and bond strength?
-More potential energy = more unstable bonds and less strong
Activation energy
-Energy input needed for a (metabolic) reaction to proceed
Transition state
-The state corresponding to the highest potential energy during a reaction
What are the factors affecting the rate of a chemical reaction? (Temperature, reactant concentration)
- Temp of the environment - increases with increasing temperature and decrease reaction rate with decreasing temp
- Higher concentration of the reactant or the enzyme will increase the reaction rate
How is an enzyme a biological catalyst?
-An enzyme speeds up metabolic reactions without consuming the molecule
How does an enzyme bind its substrate? What holds these together? (active site, induced fit)
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Why / how does an enzyme only bond one type of substrate?
-The active site of an enzyme is made to fit a specific substrate, and inhibitors can be used to control the shape of the active site
What could prevent an enzyme from binding its substrate?
-Competitive and noncompetitive inhibitors can prevent substrate binding
Substrate concentration
effect on reaction rates of enzyme catalyzed reaction
- Higher substrate concentration = higher the reaction rate, more likely to bind
- When enzyme is saturated reaction rate will reach maximum
Enzyme concentration
effect on reaction rates of enzyme catalyzed reaction
- Enzyme concentration increases, reaction rate increases (assuming substrate is abundant)
- As enzyme # increases, more collisions, more likely enzyme will collide with substrate
- Theoretically no limit when adding enzyme
Temperature
effect on reaction rates of enzyme catalyzed reaction
- Reaction rate increases and temp increases until enzyme begins to denature/unfold
- Low temp = molecules moving slow = slow rxn rate
- Human enzymes optimal temp: 35-40 C (body temp = 37)
pH
effect on reaction rates of enzyme catalyzed reaction
- Optimum closely related to the pH of the environment the enzyme usually functions/exists in
- Enzymes in mammals: 7-8
- Mouth: fairly neutral
- Stomach: highly acidic
- Beginning of small intestine: fairly basic
Presence/absence of cofactors
effect on reaction rates of enzyme catalyzed reaction
-Non-protein helpers required by many enzymes
-Cofactors of some enzymes are inorganic (ex. ions of zinc, iron, copper)
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Competitive inhibitor
effect on reaction rates of enzyme catalyzed reaction
- Bind (reversibly or irreversibly) to the active site and block the substrate from binding
- Effectiveness depends on the relative concentration of substrate and inhibitor
Non-competitive inhibitor
effect on reaction rates of enzyme catalyzed reaction
-Bind (reversibly or irreversibly) to another part of the enzyme, causing the protein to change shape, thus making the substrate catalyst less favorable/likely
Allosteric inhibitor (reversible) (effect on reaction rates of enzyme catalyzed reaction)
-Regulatory molecules that bind to enzymes and turn them “off” or decrease their activity
