metabolism + enzymes

Enzyme

Enzymes are globular proteins that act as catalysts in metabolic reactions.

Substrate

The molecule upon which an enzyme acts.

Rate of Reaction

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

Active Site

The region of an enzyme where substrate molecules bind and undergo a chemical reaction.

Induced Fit Model

The model that describes how enzymes change shape to fit the substrate upon binding.

Enzyme-Substrate Complex

The temporary complex formed when an enzyme binds to its substrate.

Collision Theory

The theory that states that for a reaction to occur, reactant particles must collide with sufficient energy.

Activation Energy

The minimum energy required for a chemical reaction to occur.

Effect of enzymes on activation energy

Enzymes lower the activation energy required for reactions.

Enzyme-substrate complex

An enzyme-substrate complex is formed, with the substrate fitting into the active site.

Reaction rate and collisions

The rate of enzyme-catalysed reactions increases when the number of collisions between substrates and active sites increases.

high temp effect

As temperature increases, particles move faster, making faster moving substrates more likely to collide with an active site.

Increasing substrate concentration effect

An increase in substrate concentration increases the chance of a substrate particle colliding with an active site, increasing the rate of reaction.

Immobilization of substrates

Large substrates, such as proteins and starch, can be immobilized to allow for repeated enzymatic hydrolysis of a macromolecule into monomers.

Immobilization of enzymes

Immobilizing an enzyme keeps it in close proximity to the substrates that it catalyses and helps maintain the stability of the enzyme.

Enzyme-Substrate Specificity

The shape and chemistry of an enzyme's active site allows one specific type of substrate to be catalysed.

denature

If an enzyme is denatured, the shape and chemistry of its active site is changed, preventing substrates from binding.

Denaturation due to Temperature

Above the optimum temperature, the enzyme becomes denatured, and the rate of reaction drops quickly.

effect of pH

A large change of pH will denature the enzyme, stopping it from working.

Effect of Substrate Concentration on Enzyme Activity

As substrate concentration increases, the rate of reaction increases until all active sites are saturated.

Enzyme Activity and pH Changes

An increase or decrease in pH from the optimum results in decreased enzyme activity.

Denaturation Effects

The enzyme will stop working if the substrate can no longer bind to the active site.

Activation energy

The minimum amount of energy required for a chemical reaction to occur.

Catalyst

increases the rate of a chemical reaction

Anabolic Reactions

Metabolic pathways that construct molecules from smaller units.

Catabolic Reactions

Metabolic pathways that break down molecules into smaller units.

Competitive Inhibition

A form of enzyme inhibition where an inhibitor competes with the substrate for binding to the active site.

Intracellular Enzymes

Enzymes that are active within the cell that they are produced in.

Extracellular Enzymes

Enzymes that are active outside of cells.

Endotherms

Organisms that maintain a constant body temperature regardless of the environment.

Competitive inhibitors

Enzyme inhibitors that bind to the active site of an enzyme, preventing the substrate from entering.

Non-competitive inhibitors

Enzyme inhibitors that bind to an allosteric site on the enzyme and must have a specific shape and chemistry.

Enzyme inhibitors

Chemicals that can bind to the enzyme and stop or slow down the activity of an enzyme.

Effect of competitive inhibitors

Competitive inhibitors compete with a substrate for the active site of an enzyme, preventing the enzyme from catalysing the reaction.

Cyclical pathways in metabolism

Pathways like the Krebs cycle and Calvin cycle that involve a series of reactions requiring specific enzymes.

Linear pathways in metabolism

Pathways like glycolysis that involve a series of reactions requiring specific enzymes.

Metabolic reactions

Chemical reactions that occur within a cell, which generate heat and are not 100% efficient, include both anabolic and catabolic pathways.

Allosteric site

A site on an enzyme where non-competitive inhibitors bind, distinct from the active site.

Effect of Substrate Concentration on Competitive Inhibition

Increasing the substrate concentration will increase the rate of enzyme activity, as more enzymes will have a substrate in the active site, and not the inhibitor.

Reaction Rate with Competitive Inhibitors

The reaction rate of the enzyme increases, even with a competitive inhibitor present, but at a slower rate than without the inhibitor.

High Substrate Concentration Effect

At very high substrate concentrations, the rate of reaction is almost the same as without an inhibitor, as there are so many substrate molecules present, the probability of the inhibitor entering the active site is very low.

Non-Competitive Inhibition

Occurs when non-competitive inhibitors bind to an allosteric site, changing the shape of the active site and preventing substrate binding.

Reversibility of Inhibitor Binding

Binding of the inhibitor to the allosteric site is reversible.

Non-Competitive Inhibitors Effect

Non-competitive inhibitors reduce the number of functioning enzymes, as enzymes with the inhibitor attached cannot catalyse the substrate.

Rate of Reaction with Non-Competitive Inhibitors

Non-competitive inhibitors reduce the reaction rate because fewer enzymes are able to catalyse the reaction.

Increase Substrate with Non-Competitive Inhibitors

Increasing substrate concentration will increase the rate of reaction, as more substrate molecules will collide with the active sites of those enzymes that are not inhibited.

Competitive Inhibitors

Shape and chemistry is similar to the substrate. Binds to the active site, blocking the substrate from entering. An increase in substrate reduces inhibition.

Non-Competitive Inhibitors

Binds to the allosteric site, which alters the shape of the active site, which prevents the substrate from entering.

Feedback Inhibition

If the first reaction is stopped, then all of the reactions will stop. This prevents an oversupply of the final product.

Penicillin

Penicillin is an antibiotic which inhibits the synthesis of bacterial cell walls.

Inhibitor

A substance that slows down or stops the activity of an enzyme.

Statins

Drugs that inhibit the enzyme HMG-CoA reductase, which plays a central role in the production of cholesterol.

Allosteric Enzymes

Enzymes that have multiple binding sites and can be regulated by molecules that bind to sites other than the active site.

Allosteric Site

The site on an enzyme where an inhibitor or activator can bind, causing a change in the enzyme's activity.

Antibiotic

A substance that kills or inhibits the growth of bacteria.