Biochemistry 3 Lecture 3: Enzymes Part I

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What is the currently most accepted model of enzyme flexibility?

Absolute specificity model

Stereochemical specificity model

Induced fit model (correct)

Lock and Key model

What is the main difference between the Lock and Key model and the Induced fit model?

The Induced fit model is less specific

The Induced fit model has a larger conformational change

The Lock and Key model is more flexible

The Lock and Key model does not allow for conformational change (correct)

What type of specificity is described by the example of glucokinase on glucose?

Structural specificity

Stereochemical specificity

Relative specificity

Absolute specificity (correct)

What is the function of trypsin in terms of peptide bonds?

It is specific to peptide bonds involving the carboxyl group of a basic amino acid Signup and view all the answers

What is the rate enhancement of enzyme-catalyzed reactions compared to uncatalyzed reactions?

10^3 to 10^8 times faster Signup and view all the answers

What is the purpose of enzyme regulation?

To respond to the needs of the cell Signup and view all the answers

Where are many enzymes localized within the cell?

In specific organelles Signup and view all the answers

What is the capability of each enzyme molecule in terms of substrate transformation?

Transforming 100 to 1000 substrate molecules into product each second Signup and view all the answers

What is the purpose of compartmentalization in enzyme reactions?

To isolate the reaction substrate or product from other competing reactions Signup and view all the answers

What type of enzymes add or remove hydrogen atoms?

Oxidoreductases Signup and view all the answers

What is the function of dehydrogenase enzymes?

To remove hydrogen atoms from a substrate Signup and view all the answers

What is the function of kinases?

To transfer phosphate groups from ATP to other molecules Signup and view all the answers

What is the function of hydrolases?

To add water across a bond, hydrolyzing it Signup and view all the answers

What is the function of lyases?

To add water, ammonia, CO2, or remove these elements to produce a double bond Signup and view all the answers

What is the function of isomerases?

To carry out many isomerization reactions Signup and view all the answers

What is the function of ligases?

To ligate two chemical groups with energy from ATP Signup and view all the answers

What is the primary nature of all enzymes?

Proteins Signup and view all the answers

Which substance accelerates the rate of chemical reactions without being consumed?

Enzymes Signup and view all the answers

What is the molecule that the enzyme acts upon called?

Substrate Signup and view all the answers

Which of the following is a correct example of an enzyme nomenclature by adding 'ase' after the name of the substrate?

Lactase Signup and view all the answers

Which enzyme action is correctly described in its name?

Glutathione reductase Signup and view all the answers

Which vitamin is associated with coenzyme TPP?

Thiamine (B1) Signup and view all the answers

What are the variant forms of enzymes called that catalyze the same chemical reaction but differ in properties?

Isozymes Signup and view all the answers

Which model suggests that the enzyme has a perfect conformation to bind the substrate?

Lock and key model Signup and view all the answers

What does an enzyme do to the activation energy of a reaction?

Decreases it Signup and view all the answers

Which of the following is NOT affected by the presence of an enzyme in a reaction?

Reaction equilibrium Signup and view all the answers

In the Michaelis-Menten model, what does 'E' stand for?

Enzyme Signup and view all the answers

What does a small Km indicate about substrate binding?

Tight substrate binding Signup and view all the answers

In the steady-state assumption, what remains constant over time?

Concentration of ES complex Signup and view all the answers

Which rate constant is associated with the formation of the product in the Michaelis-Menten model?

k2 Signup and view all the answers

What happens to enzyme activity as substrate concentration increases to high levels?

It becomes limited by enzyme availability Signup and view all the answers

What is the term used to define the maximum rate of an enzyme-catalyzed reaction?

Vmax Signup and view all the answers

What does the term $V_{max}$ denote in enzyme kinetics?

The maximum rate of reaction when enzymes are fully saturated Signup and view all the answers

At what substrate concentration is the reaction velocity ($V_0$) equal to half of $V_{max}$?

When substrate concentration is equal to $K_M$ Signup and view all the answers

What is defined as the number of substrate molecules converted to product per enzyme molecule per second?

Turnover number ($k_{cat}$) Signup and view all the answers

What describes the steady state in enzyme kinetics?

[$ES$] becomes constant Signup and view all the answers

Which equation transformed gives a linear relationship useful for data presentation?

Lineweaver-Burk equation Signup and view all the answers

What does the $K_M$ value represent?

The substrate concentration when the reaction rate is half of $V_{max}$ Signup and view all the answers

At very high substrate concentrations, $V_0$ is approximately equal to what value?

$V_{max}$ Signup and view all the answers

What term describes when the ratio of products to reactants becomes constant?

Equilibrium Signup and view all the answers