Ch 6-2 Flashcards
What is activation energy (EA)?
The energy required to start a reaction by contorting bonds into unstable states.
True or False: Enzymes alter the Gibbs free energy (ΔG) of a reaction.
False
What do enzymes do to the activation energy of a reaction?
Enzymes lower the activation energy.
True or False: Catalysts are consumed during the reaction they speed up.
False
What term describes the molecule that an enzyme binds to during a reaction?
Substrate
What complex is formed when an enzyme binds to its substrate?
Enzyme-substrate complex.
Which of the following is NOT a way enzymes lower activation energy?
a) Proper orientation of substrates
b) Increasing temperature
c) Stretching bonds
B) Increasing temp
What is the ‘induced fit’ model of enzyme activity?
It suggests that the enzyme changes shape to better fit the substrate when it binds.
What is a cofactor?
A molecule that helps enzymes bind to substrates, which can be inorganic or organic.
True or False: Vitamins can act as organic coenzymes.
True
What happens to the rate of an enzymatic reaction as the concentration of substrate increases?
The rate increases until the enzyme becomes saturated.
At what point does increasing substrate concentration no longer increase the reaction rate?
When enzyme saturation occurs.
True or False: Enzymes can be reused after catalyzing a reaction.
True
What two major factors affect enzyme activity?
Temp and pH
What is the optimal pH range for most enzymes in the human body?
pH 6-8.
What happens to an enzyme when it is exposed to temperatures above its optimal range?
The enzyme can denature, losing its function.
What is competitive inhibition?
When a molecule competes with the substrate for the enzyme’s active site.
True or False: Noncompetitive inhibitors bind to the active site of the enzyme.
False. Noncompetitive inhibitors bind to a different part of the enzyme, changing its shape.
What is allosteric regulation?
Regulation of an enzyme’s activity through the binding of molecules at a site other than the active site.
True or False: Allosteric regulation can both increase and decrease enzyme activity.
True
What role does ATP play in allosteric regulation of catabolic pathways?
ATP acts as an inhibitor.
What is feedback inhibition?
The end product of a metabolic pathway inhibits an earlier enzyme in the pathway.
True or False: Feedback inhibition helps prevent the overproduction of a product.
True
What is the term for enzymes that consist of multiple subunits and show cooperativity?
Allosteric enzymes
In feedback inhibition, where does the final product bind to stop further production?
To one of the early enzymes in the pathway.
What is the active site of an enzyme?
The region where the substrate binds to the enzyme.
What determines the specificity of an enzyme for its substrate?
The enzyme’s three-dimensional shape and chemical characteristics.
True or False: The active site of an enzyme typically interacts with only a few amino acids of the substrate.
True
What mechanism allows hemoglobin to increase its reactivity with each oxygen molecule it binds?
Cooperativity
True or False: The active site of an enzyme is rigid and cannot change shape.
False. The active site can change shape through induced fit.
Is cellular respiration an anabolic or catabolic pathway?
Catabolic
True or False: Cells operate as closed systems.
False. Cells operate as open systems.
What is the ΔG of a system at equilibrium?
Zero
What molecule provides energy for most cellular work?
ATP
True or False: ATP hydrolysis releases energy.
TRUE
How much energy is released by the hydrolysis of a single ATP molecule under cellular conditions?
Approximately 7.3 kcal/mol.
What is the role of ATP in metabolism?
ATP transfers energy from exergonic to endergonic reactions.
True or False: Enzymes are often compartmentalized in specific areas of the cell.
TRUE
How does enzyme compartmentalization benefit the cell?
It increases the opportunity for enzymes and substrates to interact, speeding up reactions.
What is a multienzyme complex?
A group of enzymes that work sequentially, with the product of one reaction becoming the substrate for the next.
Where does cellular respiration primarily occur in eukaryotic cells?
In the mitonchondria
True or False: All reactions catalyzed by enzymes are irreversible.
False. Many reactions catalyzed by enzymes are reversible.
How does the concentration of products influence the direction of enzyme-catalyzed reactions?
Higher concentrations of products can drive the reaction in the reverse direction
True or False: Catalysis by enzymes occurs at the same rate regardless of reactant concentration.
False. Reaction rates increase with higher substrate concentration until saturation is reached.
What effect does pH have on enzyme activity?
Enzymes have an optimal pH, and deviations can reduce their activity or denature them.
What is the lock-and-key model of enzyme specificity?
The enzyme’s active site is a perfect fit for the substrate, like a key fitting into a lock.
True or False: Enzymes are highly specific and will not bind to compounds that are closely related to their substrate.
True
What is the relationship between activation energy and reaction rate?
The lower the activation energy, the faster the reaction rate.
What happens to an enzyme in an environment with an extremely low pH?
The enzyme may become denatured and lose its function.
What is the transition state in a chemical reaction?
The unstable state where the reactant’s bonds have absorbed enough energy to break.
