(JUNE 2007)
24. If the Km of enzyme for substrate A is 1 x 10-6 and for substrate B is 4 x 10-8, it means
(1) Enzyme has more affinity for substrate A then substrate B
(2) Enzyme has more affinity for substrate B then substrate A
(3) Enzyme has equal affinity for substrate A and substrate B
(4) Enzyme is non-specific
The correct answer is (2) Enzyme has more affinity for substrate B than substrate A.
Introduction
The Michaelis constant (Km) is a fundamental parameter in enzyme kinetics that helps quantify the affinity between an enzyme and its substrate. A substrate with a lower Km value binds more tightly to the enzyme’s active site, indicating higher affinity. This article explains the relationship between Km and substrate affinity, interpreting the given values 1×10−6 M for substrate A and 4×10−8 M for substrate B to determine substrate preferences of the enzyme.
What Is Michaelis Constant (Km)?
-
Km is the substrate concentration at which the enzyme achieves half of its maximum reaction velocity (Vmax).
-
It is derived from kinetic constants as:
Km=k−1+kcatk1
where
k1 = rate constant for ES complex formation,
k−1 = rate constant for ES dissociation,
kcat = catalytic rate constant for product formation.
-
Strong binding (high affinity) implies that less substrate is needed to reach half-maximal velocity; thus Km is low.
-
Weak binding means higher substrate concentrations are required; Km is high.
Comparing Substrate Affinities
-
Substrate A: Km=1×10−6 M
-
Substrate B: Km=4×10−8 M
Since substrate B has a lower Km value than substrate A, the enzyme has higher affinity for substrate B.
Biological Implication of Km Differences
-
Enzymes often act preferentially on substrates they tightly bind.
-
Substrate binding affinity affects metabolic flux and enzyme competition.
-
Km values help predict substrate behavior under physiological conditions.
Common Misconception
-
Km is sometimes mistakenly described as the substrate concentration at maximum velocity; actually, it is the concentration at half-maximal velocity.
-
Affinity is inversely related to Km, not directly proportional.
Summary Table
| Substrate | Km Value (M) | Affinity to Enzyme | Interpretation |
|---|---|---|---|
| A | 1×10−6 | Lower | Requires higher substrate concentration for effective binding |
| B | 4×10−8 | Higher | Binds more strongly; effective at lower substrate concentrations |
Conclusion
The enzyme exhibits greater affinity for substrate B than substrate A, as indicated by the significantly lower Michaelis constant for substrate B. This fundamental concept guides understanding of enzyme specificity, kinetics, and function in biochemical pathways, crucial for academic and research success in life sciences.
Understanding Km allows for predictive insights into enzyme-substrate interactions, pathway regulation, and therapeutic target identification in biochemistry and molecular biology.
49 Comments
Aakansha sharma Sharma
September 12, 2025The enzyme exhibits greater affinity for substrate B than substrate A,
Priya dhakad
September 12, 2025substrate B has a lower Km value than substrate A , the enzyme has higher affinity for substrate B then substrate A .
Varsha Tatla
September 12, 2025Done sir ✅
Dharmpal Swami
September 13, 2025Substrate B has lower value of km so affinity of B is higher than substrate A
Mansukh Kapoor
September 13, 2025The correct answer is option 2nd
Enzyme has more affinity for substrate B than substrate A
Kirti Agarwal
September 13, 2025Enzyme has more affinity for substrate b
Khushi Vaishnav
September 13, 2025Enzyme has more affinity for substrate B than substrate A.
Kanica Sunwalka
September 13, 2025km is 1/2 of Vmax
km more => affinity less
so , enzyme has more affinity for Substrate B than A
Bhawna Choudhary
September 13, 2025Enzyme has more affinity for substrate B then substrate A because km vale of substrate B is less
Sakshi Kanwar
September 13, 2025Km is inversely proportional to affinity that means enzyme B has more binding affinity than A for the substrate
Mohd juber Ali
September 14, 2025Km value for sub. A = 1✖️10^-6 (0.000001
Km value for sub B = 4✖️10^-8 (0.00000004
Km value of sub A is more in compaire of B
Km(A) >km(B)
Affinity of substarte b is more
Pratibha Jain
September 14, 2025correct answer is option (2)
Enzyme has more affinity for substrate B than substrate A.
Aafreen Khan
September 14, 2025Enzyme has more affinity for substrate B than substrate A and substrate B has a lower Km value than substrate A
Soniya Shekhawat
September 14, 2025Enzyme afinity of substate B is more as compared to A substrate because B may km ki value kam hai.
Pooja
September 14, 2025Option b is correct
Enzyme has more affinity for substrate B than substrate A
Ayush Dubey
September 14, 2025Enzyme has more affinity for substrate B than substrate A
Tanvi Panwar
September 14, 2025enzyme has more affinity for substrate B than substrate A bcz its km id lower as compared to substrate A.
Payal Gaur
September 14, 2025Option B. The value of km is less for substrate B so high affinity of B and km value for substrate A is more (affinity low)
Kajal
September 14, 2025Option 2 Enzyme has more affinity for substrate B than substrate A is correct .
Khushi Agarwal
September 14, 2025The correct answer is B
Enzyme has more affinity for substrate B than substrate A
Anurag Giri
September 14, 2025The correct answer is option 2nd
Enzyme has more affinity for substrate B than substrate A
Neha Yadav
September 14, 2025Km is inversely proportional to affinity so enzyme has more affinity for substrate B than substrate A
Rishita
September 14, 2025Option b is correct.. affinity high then km is low
Anju
September 14, 2025Ans: enzyme shows high affinity for B as compare to A
Santosh Saini
September 14, 2025Enzymes has more affinity for substrate B than substrate A
Avni
September 14, 2025Enzyme has more affinity for substrate B than substrate A. low Km so high affinity .
Vanshika Sharma
September 14, 2025Enzymes has more affinity for subs B then subs A
HIMANI FAUJDAR
September 14, 2025Ans 2, substrate B has a lower Km value than substrate A, the enzyme has higher affinity for substrate B.
anjani sharma
September 14, 2025Substrate B has lower value of km so affinity of B is higher than substrate A
Pallavi Ghangas
September 14, 2025Enzyme has more affinity for substrate B than substrate
Heena Mahlawat
September 14, 2025Enzyme having high km value means low affinity and low km value means high affinity, so substrate B having low km value have high affinity
Mitali saini
September 14, 2025The correct answer is (2) Enzyme has more affinity for substrate B than substrate A.
Nilofar Khan
September 15, 2025correct answer is (2)
Enzyme has more affinity for substrate B than substrate A.
Km is inversely proportional to affinity
Priyanshi sharma
September 15, 2025Enzyme has more affinity for substrate
Deepika sheoran
September 15, 2025Option 2nd is correct
Enzyme has more affinity for substrate B than substrate A.
yashika
September 15, 2025Km is inverversely pROPORTIONAL TO affinity
Asha Gurzzar
September 15, 2025Enzyme has more affinity for substrate b than substrate a option 2is correct
Muskan singodiya
September 15, 2025Enzyme has more affinity for subtrate b than subtrate a
Simran Saini
September 15, 2025The correct answer is option 2nd
Enzyme has more affinity for substrate B than substrate A.
Arushi Saini
September 15, 2025Option B is correct Substrate B has lower value of km so affinity of B is higher than substrate A
yashika
September 16, 2025Affinity is inversely proportional TO km
Anjana sharma
September 16, 2025Enzyme has more affinity for substrate B than substrate A.
Sonal nagar
September 16, 2025Option 2
Enzyme has more affinity for substrate B than substrate A.
Minal Sethi
September 16, 2025High Km means low affinity, more dissociation so option b is correct
Deepika sheoran
September 16, 2025Option b
Enzyme has more affinity for substrate B than substrate A.
Alec
September 16, 2025Enzyme has more affinity for substrate B than A.
Palak Sharma
September 16, 2025substrate B has a lower Km value than substrate A , the enzyme has higher affinity for substrate B then substrate A .
Muskan Yadav
September 17, 2025Enzyme has more affinity for substrate B than substrate A.
and B has lower km value than substrate A the enzyme has high affinity for substrate B .
Khushi Singh
September 25, 2025Lower km value = higher affinity