1) Which of the following is true for all enzymes? They provide energy for ender
ID: 208783 • Letter: 1
Question
1) Which of the following is true for all enzymes?
They provide energy for endergonic reactions.
They decrease G.
They alter the transition state.
They harness energy from ATP.
2) Which of the following statements is TRUE?
X + Y + ATP <=> X-P + Y + ADP <=> Z + ADP + Pi
Is ATP an enzyme for this reaction?
0.00277; exergonic
0.00277; endergonic
361; exergonic
361; endergonic
Yes, because it alters the transition state
Yes, because it increases the rate of the reaction
Yes, because it provides energy to get over the activation energy barrier
No, because it is irreversibly altered by the reaction
No, because it does not alter the transition state
4) Consider the reaction: A + B <=> C + D. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 0.1 M, [B] = 0.1 M, [C] = 1.9 M, and [D] = 1.9 M; and the pH is 7.0. Keq for the reaction is _____ and the reaction is _____. (Believe it or not, you shouldn't need a calculator for this!)
The entropy of a closed system never increases.
The sign (+ or -) of the change in enthalpy tells you whether a reaction is exergonic or endergonic.
For any process to be energetically favorable, G must be < 0.
If the free energy of the products (Gproducts) is greater than that of the reactants (Greactants) the reaction is favorable.
Both the 2nd and 3rd answers above
3) ATP hydrolysis provides the energy for the endergonic reaction: X + Y <=> Z . The mechanism by which this occurs is that compound X is phosphorylated using the phosphate group from ATP. dephosphorylation of X, which itself is exergonic, makes it possible for X and Y to combine to form Z. In this scheme X-P can be considered the transition state. The entire reaction, including ATP is as follows:
They provide energy for endergonic reactions.
They decrease G.
They alter the transition state.
They harness energy from ATP.
2) Which of the following statements is TRUE?
X + Y + ATP <=> X-P + Y + ADP <=> Z + ADP + Pi
Is ATP an enzyme for this reaction?
0.00277; exergonic
0.00277; endergonic
361; exergonic
361; endergonic
Yes, because it alters the transition state
Yes, because it increases the rate of the reaction
Yes, because it provides energy to get over the activation energy barrier
No, because it is irreversibly altered by the reaction
No, because it does not alter the transition state
4) Consider the reaction: A + B <=> C + D. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 0.1 M, [B] = 0.1 M, [C] = 1.9 M, and [D] = 1.9 M; and the pH is 7.0. Keq for the reaction is _____ and the reaction is _____. (Believe it or not, you shouldn't need a calculator for this!)
The entropy of a closed system never increases.
The sign (+ or -) of the change in enthalpy tells you whether a reaction is exergonic or endergonic.
For any process to be energetically favorable, G must be < 0.
If the free energy of the products (Gproducts) is greater than that of the reactants (Greactants) the reaction is favorable.
Both the 2nd and 3rd answers above
3) ATP hydrolysis provides the energy for the endergonic reaction: X + Y <=> Z . The mechanism by which this occurs is that compound X is phosphorylated using the phosphate group from ATP. dephosphorylation of X, which itself is exergonic, makes it possible for X and Y to combine to form Z. In this scheme X-P can be considered the transition state. The entire reaction, including ATP is as follows:
Explanation / Answer
Answer 1.
Endergonic reaction require energy from outside for the reaction to proceed further. Enzymes do not provide energy for the reaction. They take the energy from some energy source like ATP, GTP, NADH etc. So, statements ‘a’ and ‘d’ are incorrect. Note that the statement ‘d’ states that enzymes take energy only from ATP, which is not true; the energy can be harnessed from other molecules also like GTP, NADH2 etc.
Enzymes decrease the Gibbs free energy of activation, but it does not change the overall free energy of the reaction. So, the statement ‘b’ stating that ‘they decrease G is untrue.
The correct statement is ‘c’. Enzymes always lower the activation energy of the reaction and alter the transition state of the reaction.
Answer 2.
ATP is not an enzyme, and it never acts as enzyme. It is the energy providing molecule. In the first reaction, among ‘X’ and ‘Y’, one is substrate and the other is enzyme.
Note that none of the options are correct. In fact the question is incorrect.
Answer 4.
Keq = (1.9 * 1.9) / (0.1 * 0.1) = 361
Since this reaction is not using ATP, so it can be said that ‘A’ and ‘B’ are providing the energy for the forward reaction and ‘C’ and ‘D’ will provide energy for the reverse reaction.
So, the reaction is exothermic.
The correct answer is ‘c’ (361, exergonic)
Answer 3.
Options for this answer are not clear at all.
Please post this one again, with the question first and the options following the question.
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