Chapter 2 - Enzymes and Kinetics

Comprehensive practice flashcards covering enzyme classification, kinetics, thermodynamics, models of activity, and inhibition mechanisms based on the lecture notes.

Enzymes are __________ that catalyze reactions in the body, remaining unchanged and reusable.

proteins

Enzymes affect __________ by making reactions go faster, but they do not change the thermodynamics of a reaction.

kinetics

Catalysts exert their effect by lowering the __________ of a reaction.

activation energy

Enzymes do not alter the __________ constant, meaning they do not change how much total product is formed at equilibrium.

equilibrium

The loss of an enzyme's structure due to extreme pH or temperature is called __________.

denaturation

Enzymes that catalyze oxidation-reduction reactions involving the transfer of electrons are called __________.

Oxidoreductases

A __________ catalyzes the movement of a functional group from one molecule to another, such as a kinase.

Transferase

__________ catalyze hydrolysis reactions by breaking a bond using a water molecule.

Hydrolases

Enzymes that catalyze the cleavage of a single molecule into two products without the use of water are called __________.

Lyases

The mnemonic LIL HOT stands for Lyases, Isomerases, Ligases, Hydrolases, Oxidoreductases, and __________.

Transferase

An __________ reaction requires energy input and has a $\Delta G > 0$.

endergonic

An __________ reaction is one where energy is given off and has a $\Delta G < 0$.

exergonic

The physical interaction between an enzyme and its molecule of action is called the __________ complex.

enzyme-substrate

The __________ Theory suggests that the active site is already in the correct conformation for the substrate to bind.

Lock & Key

The __________ Model suggests that the enzyme changes shape upon binding to a substrate for a more precise fit.

Induced Fit

Enzymes without their required cofactors are called __________, while those with them are called holoenzymes.

apoenzymes

Coenzymes are small organic molecules that are often derived from __________.

vitamins

When every active site of an enzyme population is occupied by substrate, the enzyme is said to be at __________.

saturation

The substrate concentration at which half of the enzyme's active sites are full is defined as the __________.

$$K_m$$

A low $K_m$ reflects a __________ affinity for the substrate.

high

The number of substrate molecules one enzyme converts into product per second when fully saturated is the __________.

$$k_{cat}$$

The Lineweaver-Burk plot uses the x-intercept to determine __________.

$$-\frac{1}{K_m}$$

Enzymes with multiple subunits that show a sigmoidal curve exhibit __________.

cooperativity

If the Hill's coefficient is __________, the enzyme shows positive cooperativity.

1

Enzymes that show no cooperativity follow __________ kinetics.

Michaelis-Menten

The low-affinity state of a cooperative enzyme is called the __________ state.

T

Enzyme-catalyzed reactions tend to double in speed for every $10\,^\circ\text{C}$ increase until the __________ temperature is reached.

optimum

__________ inhibition involves an inhibitor binding to the active site, which can be overcome by adding more substrate.

Competitive

In competitive inhibition, $V_{max}$ remains unchanged but $K_m$ __________.

increases

In __________ inhibition, the inhibitor binds to an allosteric site regardless of whether substrate is bound, decreasing $V_{max}$ while $K_m$ stays the same.

noncompetitive

__________ inhibition occurs when an inhibitor binds only to the enzyme-substrate complex, lowering both $K_m$ and $V_{max}$.

Uncompetitive

Enzymes that are secreted in an inactive form and must be activated by cleavage are called __________.

zymogens