Ch 7 Enzyme Activity Flashcards
What does the Michaelis–Menten equation describe?
Enzyme kinetics with hyperbolic characteristics
What does Vmax represent in the Michaelis–Menten equation?
The maximum rate of reaction
What is the relationship expressed by the Michaelis–Menten equation?
V = Vmax[S] / (KM + [S])
What type of plot is a Lineweaver-Burk plot?
A plot of 1/V versus 1/[S]
In a Lineweaver-Burk plot, what does the x-intercept represent?
-1/KM
What does the turnover number (kcat) measure?
Moles of substrate converted to product per unit time by a mole of enzyme
What is the turnover number for Carbonic anhydrase?
1,000,000 s–1
Who won the Nobel Prize in Chemistry in 2018 for directed evolution of enzymes?
Francis Arnold
What is a competitive inhibitor?
A substance that competes with the substrate for the active site
True or False: A competitive inhibitor changes Vmax.
False
What happens to KM in the presence of a competitive inhibitor?
KM increases
What is the effect of noncompetitive inhibition on Vmax?
Vmax decreases
In noncompetitive inhibition, what happens to KM?
KM remains unchanged
What is feedback inhibition?
Formation of a product inhibits its continued production
What is an allosteric enzyme?
A multi-subunit protein whose activity is affected by other substances binding to it
What are allosteric effectors?
Substances that modify the behavior of an allosteric enzyme
What is the role of kinases in enzyme activity?
They attach phosphates to proteins
What is a zymogen?
An inactive precursor of an enzyme
What is the active form of chymotrypsinogen called?
α-chymotrypsin
What type of modification can activate an enzyme?
Phosphorylation
What does the concerted model of allosteric enzymes imply?
The enzyme can only exist in the T or R states
Fill in the blank: A protein that controls enzyme activity through phosphorylation of amino acid side chains is called a _______.
kinase
Which of the following is an example of a co-enzyme: ATP, a zymogen, biotin, or ATCase?
Biotin
Which type of inhibition allows increased substrate concentration to overcome the inhibitor?
Competitive inhibition
What does a suicide inhibitor do?
Acts irreversibly on the enzyme
What is a co-enzyme example?
Biotin
Biotin is a vitamin that acts as a co-enzyme in various biochemical reactions.
What is the inactive form of chymotrypsin called?
Chymotrypsinogen
Chymotrypsinogen is an inactive precursor that is activated to chymotrypsin.
Which enzyme cleaves chymotrypsinogen?
Trypsin
Trypsin activates chymotrypsinogen by cleaving it.
Where is chymotrypsinogen stored?
Pancreas
Chymotrypsinogen is stored in the pancreas before being activated.
True or False: Chymotrypsinogen is a multimeric enzyme.
False
Chymotrypsinogen is a single polypeptide chain and not multimeric.
What is the hydrogen ion concentration in an aqueous solution when the pH is 7.5?
~3.3 X 10^-8 M
The hydrogen ion concentration can be calculated using the formula [H+] = 10^(-pH).
What is the pH in water when the hydrogen ion concentration is ~3.3 X 10^-7 M?
~6.5
The pH can be determined using the formula pH = -log[H+].
