Enzymes Part 2 Flashcards
(28 cards)
What are the two types of modifications that alter the rate of enzyme reactions?
Covalent and noncovalent modifications
What term is used for non-protein components required for enzymatic activity?
Cofactors
What is the active enzyme called when it includes its non-protein components?
Holoenzyme
What is the term for the inactive protein component of an enzyme?
Apoenzyme
What are the two main categories of cofactors?
- Metal ions
- Organic molecules
What are coenzymes?
Organic cofactors that bind temporarily and detach after catalysis
What are prosthetic groups?
Organic cofactors that are permanently bound to the enzyme
What is an example of a metalloprotein?
Hemoglobin
What is the difference between metalloproteins and metal-activated enzymes?
Metalloproteins contain permanently bound metal ions; metal-activated enzymes temporarily bind metal ions
What does the induced fit model describe?
The binding of enzyme and substrate leading to a conformational change
What is the role of residues in the active site of enzymes?
Interact with substrates and can form temporary covalent bonds with reaction intermediates
What type of specificity does an enzyme with absolute specificity have?
Catalyzes the reaction of only one substance
What does Km (Michaelis constant) represent?
The substrate concentration at which the reaction rate is 50% of Vmax
What does a lower Km value indicate about an enzyme?
Higher affinity for its substrate
What is Kcat?
The turnover number, or the number of substrate molecules converted to product per second
What does Kcat/Km represent?
Catalytic efficiency
Fill in the blank: The optimal temperature for human enzymes is _______.
37°C
What regulates enzyme activity at the transcriptional level?
Histone modifications that affect DNA accessibility
What are zymogens?
Inactive forms of enzymes that require proteolytic cleavage to become active
What is the function of hexokinase?
Catalyzes glucose uptake in all cells
What distinguishes glucokinase from hexokinase?
Glucokinase has a higher Km and acts as a glucose sensor
What does an elevation of lactate dehydrogenase (LDH) indicate?
Tissue damage or disease
What is the role of glucose oxidase in diagnostics?
Catalyzes glucose oxidation to produce detectable color changes
What is the function of EDTA in blood sample analysis?
Prevents clotting by chelating calcium
