40 Questions
What is the currently most accepted model of enzyme flexibility?
Induced fit model
What is the main difference between the Lock and Key model and the Induced fit model?
The Lock and Key model does not allow for conformational change
What type of specificity is described by the example of glucokinase on glucose?
Absolute specificity
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
What is the rate enhancement of enzyme-catalyzed reactions compared to uncatalyzed reactions?
10^3 to 10^8 times faster
What is the purpose of enzyme regulation?
To respond to the needs of the cell
Where are many enzymes localized within the cell?
In specific organelles
What is the capability of each enzyme molecule in terms of substrate transformation?
Transforming 100 to 1000 substrate molecules into product each second
What is the purpose of compartmentalization in enzyme reactions?
To isolate the reaction substrate or product from other competing reactions
What type of enzymes add or remove hydrogen atoms?
Oxidoreductases
What is the function of dehydrogenase enzymes?
To remove hydrogen atoms from a substrate
What is the function of kinases?
To transfer phosphate groups from ATP to other molecules
What is the function of hydrolases?
To add water across a bond, hydrolyzing it
What is the function of lyases?
To add water, ammonia, CO2, or remove these elements to produce a double bond
What is the function of isomerases?
To carry out many isomerization reactions
What is the function of ligases?
To ligate two chemical groups with energy from ATP
What is the primary nature of all enzymes?
Proteins
Which substance accelerates the rate of chemical reactions without being consumed?
Enzymes
What is the molecule that the enzyme acts upon called?
Substrate
Which of the following is a correct example of an enzyme nomenclature by adding 'ase' after the name of the substrate?
Lactase
Which enzyme action is correctly described in its name?
Glutathione reductase
Which vitamin is associated with coenzyme TPP?
Thiamine (B1)
What are the variant forms of enzymes called that catalyze the same chemical reaction but differ in properties?
Isozymes
Which model suggests that the enzyme has a perfect conformation to bind the substrate?
Lock and key model
What does an enzyme do to the activation energy of a reaction?
Decreases it
Which of the following is NOT affected by the presence of an enzyme in a reaction?
Reaction equilibrium
In the Michaelis-Menten model, what does 'E' stand for?
Enzyme
What does a small Km indicate about substrate binding?
Tight substrate binding
In the steady-state assumption, what remains constant over time?
Concentration of ES complex
Which rate constant is associated with the formation of the product in the Michaelis-Menten model?
k2
What happens to enzyme activity as substrate concentration increases to high levels?
It becomes limited by enzyme availability
What is the term used to define the maximum rate of an enzyme-catalyzed reaction?
Vmax
What does the term $V_{max}$ denote in enzyme kinetics?
The maximum rate of reaction when enzymes are fully saturated
At what substrate concentration is the reaction velocity ($V_0$) equal to half of $V_{max}$?
When substrate concentration is equal to $K_M$
What is defined as the number of substrate molecules converted to product per enzyme molecule per second?
Turnover number ($k_{cat}$)
What describes the steady state in enzyme kinetics?
[$ES$] becomes constant
Which equation transformed gives a linear relationship useful for data presentation?
Lineweaver-Burk equation
What does the $K_M$ value represent?
The substrate concentration when the reaction rate is half of $V_{max}$
At very high substrate concentrations, $V_0$ is approximately equal to what value?
$V_{max}$
What term describes when the ratio of products to reactants becomes constant?
Equilibrium
Learn about enzymes, catalysts, substrates, and isozymes in biochemistry. This lecture covers the definitions and concepts of enzymes and their role in biological reactions.
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