Enzymes Flashcards

Flashcards covering key vocabulary and concepts related to enzymes, enzyme activity, and enzyme inhibition.

Enzymes

Globular proteins with a tertiary structure synthesized by living cells, acting inside (intercellular) or secreted by cells (extracellular).

Active Site

A 3D space on an enzyme molecule where specific substrate molecule(s) can fit and bind.

Enzyme-Substrate Complex

Formed when a substrate binds to the active site of an enzyme through interactions with R groups/polar atoms of the amino acids.

Activation Energy

The energy needed for a reaction to take place; reduced by enzymes acting as biological catalysts.

Enzyme Specificity

Each enzyme is specific to a particular substrate, requiring different enzymes even for the same reaction on different substrates.

Lock and Key Hypothesis

Theory where the active site in the enzyme is like a lock into which only one substrate molecule can fit like a key.

Induced Fit Hypothesis

Theory where the shape of the active site changes slightly as the substrate binds, strengthening bonds and weakening bonds in the substrate.

Effect of pH on Enzymes

Changes in pH can alter bonding between amino acids, changing the enzyme's secondary and tertiary structure, potentially inactivating or denaturing it.

Optimum pH

The pH at which the shape of the active site enables bonds to form successfully with the substrate, resulting in the greatest frequency of enzyme-substrate complex formation and highest rate of reaction.

Effect of Temperature on Enzymes

Temperature increases particle kinetic energy; up to the optimum temperature, collisions increase and reaction rate rises; above optimum, bonds break and the enzyme denatures.

Optimum Temperature

The temperature at which the maximum number of enzyme-substrate complexes are forming at the same time, and the rate reaches a maximum (Vmax).

Effect of Substrate Concentration on Enzyme Activity

At low substrate concentration, the rate of reaction increases as substrate concentration increases and more active sites are occupied. At higher concentrations, active sites become saturated, reaching a maximum rate (Vmax).

Effect of Enzyme Concentration on Enzyme Activity

At low enzyme concentration, the rate of reaction increases as enzyme concentration increases and more active sites become available. At higher concentrations, substrate becomes the limiting factor, reaching a maximum rate (Vmax).

Calculating Reaction Rate (from time)

If the dependent variable is time: rate = 1 / time

Calculating Reaction Rate (from quantity)

If the dependent variable is a quantity: rate = quantity / time

Calculating Rate (from graph)

Rate between two times: (change in y axis value) / (change in x axis value). Initial rate: draw a tangent going through zero. Rate at a particular time: for rate in a particular point draw a tangent.

Purpose of a Control

A standard experiment test which has identical variables to the main set up, except the one being investigated, so that details of its effects may be discovered by comparison.

Enzyme Inhibitors

Substances that slow down or stop enzyme action; needed in cells to control reactions that are no longer needed.

Competitive Inhibition

A substance with a similar shape to the substrate binds to the active site, blocking it and reducing the rate of reaction. Increasing substrate concentration can overcome this.

Non-Competitive Inhibition

A substance binds to the enzyme at the allosteric site, changing the shape of the active site and preventing substrate binding. The maximum reaction rate cannot be achieved even with high substrate concentrations.

Allosteric Site

The site on an enzyme where a non-competitive inhibitor binds, altering the shape of the active site.

End-Product Inhibition

A metabolic reaction controlled by the end-product acting as a non-competitive, reversible inhibitor on the original enzyme, forming a feedback loop.

Buffer

Chemicals that can maintain a constant pH.