Enzymes and Energy Presentation AP Bio

Reactant(s)

Substances that undergo change in a chemical reaction.

Product(s)

Substances that are produced in a chemical reaction.

Enzyme

Biological catalysts that speed up chemical reactions in the body.

Catabolism

reactions that break down biological polymers into monomers to help generate ATP.

Anabolism

reactions that build up monomers into biological polymers for energy storage.

Free energy

Energy that is actually available for a cell to use for metabolic processes.

Exergonic reactions

Reactions that release free energy that is used by endergonic reactions.

Endergonic reactions

Reactions that require a net investment of free energy into the bonds between the monomers.

Reaction coupling

The process where exergonic reactions release free energy that is captured and used to make endergonic reactions able to occur.

Dehydration synthesis

An anabolic chemical reaction that forms covalent bonds between monomers to build polymers of biomolecules, with water as a byproduct.

Hydrolysis

A catabolic chemical reaction that breaks the covalent bonds between monomers to break polymers into monomers, using water as a reactant.

Active Site

The part of an enzyme where the substrate binds.

Substrate

Reactant that is changed by the enzyme.

Enzyme-Substrate Complex

The state when the enzyme and substrate are bound together.

Induced Fit Model

A model describing how the enzyme changes shape to surround the substrate during binding.

Enzyme Structure

Includes the active site that specifically interacts with substrate molecules.

Compatibility of Substrate

For an enzyme-mediated chemical reaction to occur, the shape and charge of the substrate must be compatible with the active site of the enzyme.

Enzymes are reusable

Enzymes are not used up or changed in the reaction.

Homeostasis

The maintenance of stable internal conditions in the body, which enzymes help achieve.

Conformational change

The change in shape of an enzyme when the substrate binds to it.

Enzymes

Biological catalysts that facilitate chemical reactions in cells by lowering the activation energy.

Activation Energy

The energy required for a chemical reaction to occur.

Amylase

A mouth enzyme that breaks down starch.

Pepsin

A stomach enzyme that breaks down proteins.

Optimal Conditions

Conditions in which enzymes work at their most efficient.

Denaturation

The process in which enzymes lose their ability to catalyze reactions due to extreme conditions.

Enzyme Efficiency

A measure of how close to the maximum rate an enzyme can catalyze reactions.

Factors Affecting Enzyme Efficiency

Optimal temperature and pH, substrate concentration, enzyme concentration, product concentration, and presence of inhibitors.

Suboptimal Temperatures

Lack of energy that decreases the amount of collisions between the enzyme and substrate, slowing or stopping the reaction rate.

Above Optimal Temperatures

Too much energy that causes amino acid side chains to move faster, disrupting weak interactions and leading to denaturation.

Hydrolysis in Digestion

Enzymes in the intestines use hydrolysis to break food into nutrients.

Small Intestine Function

Absorbs nutrients into the bloodstream so they can reach cells that need them.

Chemical Reactions Requiring Enzymes

Dehydration Synthesis and Hydrolysis are chemical reactions that require enzymes to occur.

Enzyme-Substrate Collisions

Increasing temperature up to optimal rate increases the speed of enzyme-substrate collisions, thus increasing the reaction rate.

Maximum Rate of Enzymes

Enzymes have a maximum rate at which they can catalyze reactions, which is different for each enzyme.

Cellular Environment

The environment in which enzymes operate, affecting their activity and efficiency.

Nutrient Absorption

The process by which the small intestine absorbs nutrients into the bloodstream.

Chemical Reaction Rate

The speed at which reactants are converted into products in a chemical reaction.

Enzyme Concentration

The amount of enzyme present in a reaction, which can affect the reaction rate.

Substrate Concentration

The amount of substrate present in a reaction, which can affect the reaction rate.

Denatured enzymes

Do not have proper active site shape, and cannot interact with substrates.

Effect of pH on enzymes

Raising the pH causes H+ ions to break hydrogen bonds and ionic interactions, disrupting secondary and tertiary structure and causing denaturation of the enzyme.

Basic pH

Substances with basic pH's have a high concentration of OH- ions.

Effect of substrate concentration on enzyme rate

Changing substrate concentration will affect the enzyme rate by altering the likelihood and speed with which the enzyme and substrate will collide.

Decreasing substrate concentration

Will slow the reaction rate.

Increasing substrate concentration

Will increase reaction rate.

Maximum rate for an enzyme

Rate can only increase up to the maximum rate for that enzyme because at max rate 100% of the enzyme is occupied by substrate.

Cofactors

Non-protein, small inorganic compounds & ions bound within enzyme molecule.

Examples of cofactors

Mg, K, Ca, Zn, Fe, Cu.

Coenzymes

Non-protein, organic molecules that bind near the active site and assist reactions.

Examples of coenzymes

NAD+ (niacin; B3), FADH (riboflavin; B2).

Competitive inhibition

a type of enzyme inhibition where a molecule, similar in structure to the normal substrate, binds to the enzyme's active site and blocks the substrate from binding.

Non-competitive inhibition

Inhibitor binds to a different place on the enzyme called the allosteric (other) site.

Inhibitors

Can bind reversibly or irreversibly. Irreversible inhibitors permanently deactivate an enzyme.

Negative feedback inhibition

Metabolic pathways are series of chemical reactions with multiple steps, each catalyzed by a separate enzyme, allowing better control.

Role of intermediates in negative feedback

Sometimes an intermediate OR a final product of the pathway will act as an inhibitor of enzymes in the pathway.

Effect of inhibiting enzyme 3

Substrate B would build up in the cell because it couldn't be converted to intermediate C.

Effect of inhibiting enzyme 5

Substrate D would build up in the cell because it couldn't be converted into isoleucine.

Interpreting enzyme graphs

Determine the optimal temperature or pH by finding the peak on the graph.