Metabolism includes all the reactions in an organism. Catabolic and anabolic pathways (series of reactions) intertwine to breakdown molecules (often the food we eat) to provide energy or to use energy to build up biomolecules.
Getting into bioenergetics a little more, we’ll need to understand those energy transformations. In particular, the concept of energy coupling of reactions, which then involves understanding how proteins work.
Try these questions. Publish your answers in the comments to one, some or all.
- How would you label the three components (a, b, and c) of the ATP molecule in the image below?
- In the image above, which bond(s) is/are likely to break? And, name the chemical mechanism by which this bond is broken.
- Explain why this reaction releases so much energy.
- In the figure illustrating an exergonic reaction below, indicate the correct labels for a-e.
- Both ATP and ADP serve as regulators of enzyme activity. In catabolic pathways, which of these two molecules would you predict acts as an inhibitor? Which one acts as an activator?
- Why are catabolic and anabolic pathways often coupled in a cell?
- When a cell breaks down glucose, only about 34% of the energy is captured by ATP. According to the 2nd law of thermodynamics, what happens to the other 66% of the energy?
- In reference to enzymes and substrates, what is meant by an “induced fit”?
- When substance A was added to an enzyme reaction, product formation was decreased. The addition of more substrate did not increase product formation. What could substance A be?
HTK General Biology 2 
1. ATP is a molecule composed of a. Adenine b. Ribose sugar and c. three phosphate groups
2. The bond between the phosphate group on the left and the phosphate group in the middle of the trio is the bond that breaks through the process of hydrolysis.
3. the hydrolysis of the phosphate group releases energy (despite the fact that breaking bonds requires energy) because the free energy of the reactants is greater than the free energy of the products. in other words the products are more stable than the reactants. aside from being more stable the products also increase entropy which is a favored quality of a reaction.
4. a. Gibbs Free Energy b. (I don’t know) c. Activation energy of an uncatalyzed reaction d. Activation energy of a catalyzed reaction e. delta G (which stands for change in Gibbs free energy)
5. ATP acts as an activator while ADP acts as an inhibitor. this is due to the fact that ATP when broken down releases energy that can be used to activate chemical processes in the cell. if ADP uses the energy released by the ATP to become ATP instead of allowing the energy to serve another function it is inhibiting certain processes that require energy. (hope that’s clear and also correct of course)
to be continued…
LikeLiked by 1 person
Answer 4b) is transition state
Answer 5) ATP would act as an inhibitor to catabolic pathways, slowing the breakdown of fuel molecules if the supply of ATP exceeds demand. If ATP supplies drop, ADP would act as an activator of these catabolic enzymes, and more ATP would be produced.
LikeLike
1. A) Adenine Base.
B) Ribose.
C) Triphosphate.
2. the first -P-O-P- bond in the triphosphate is hydrolyzed to release energy. after hydrolysis, the ATP becomes ADP ( Adenosine Diphosphate).
3. Since ATP is an unstable molecule, its breakdown to more stable component release energy as the high-energy phosphoanhydride bonds break.
4. A) Gibbs Free Energy (G).
B) Transition State.
C) Activation Energy of Uncatalyzed Reaction.
D) Activation Energy of Catalyzed Reaction.
E) Delta G (change in Gibbs Energy).
5. ADP would be the inhibitor. Since its a result of a breakdown of ATP (the activator) which releases energy, allowing ADP to use this to become ATP. Thus, reversing its effects.
6.the energy that is released from one pathway is used to “activate” the other, since one is endergonic and the other is exergonic.
7. the 66% of energy would convert to other types of energy such as heat that will radiate from the cell.
8. The introduction of an enzyme to a substrate causes the dynamic location of the enzyme to alter shape in arrange to permit the enzyme and substrate to bond together. in a similar but more fit mechanism of lock-and-key.
9. Non-competitive inhibitor.
LikeLiked by 2 people
Answer 5) ATP would act as an inhibitor to catabolic pathways, slowing the breakdown of fuel molecules if the supply of ATP exceeds demand. If ATP supplies drop, ADP would act as an activator of these catabolic enzymes, and more ATP would be produced.
Just to clarify Answer 8: The binding of the substrate changes the shape of the active site, which can stress or bend substrate bonds.
LikeLike
Question 9’s answer is allosteric inhibition (or noncompetitive inhibition). correct.
LikeLike
#5. As I understand it, catabolic pathways release energy, so they release ATP. Therefore, ATP would be the inhibitor: when too much of it is produced via catabolic pathways, ATP molecules will go inhibit the enzymes of upstream reactions, hence reducing or stopping the production of more ATP. Corollary, ADP would act as a the activator, since having too much ADP will trigger the cell to produce more ATP (ADP will activate the enzymes that catalyze the production of ATP).
But I am not sure for this question because if we consider the catabolic reaction:
ATP –> ADP + Pi
then ATP would be the activator and ADP would be the inhibitor, like Zaki said…
So I am really not sure!
LikeLiked by 1 person
Your first answer is correct Elsa. Think of if via negative feedback inhibition.
LikeLike
#6. They are often coupled in cells because catabolic pathways are exergonic and anabolic pathways are endergonic. For the anabolic reaction to occur, it needs energy. Coupling it with an exergonic reaction through the phosphorylation of a substrate or an enzyme will increase the potential energy of the reactants and render the overall reaction exergonic. In summary, energetic coupling is necessary for the anabolic reactions to occur.
#9. Could it be a regulatory molecule (doing allosteric deactivation) as well as a competitive inhibitor?
LikeLiked by 2 people
Good answer for Question 6
Question 9 is only allosteric (or noncompetitive) inhibition. It cannot be a competitive inhibitor since increasing substrate concentration does not overwhelm the effect of inhibition, so that means the inhibitor is not acting in the active site.
LikeLike