Energy and Enzymes

Question 1

What is anabolism?

Answer 1

building-up process where smaller molecules are combined to form larger, more complex molecules, requiring energy

Question 2

What is catabolism?

Answer 2

breaking-down process where larger molecules are converted into smaller ones, releasing energy

Question 3

What is metabolism?

Answer 3

set of chemical reactions that convert molecules into other molecules and transfer energy in living organisms

Question 4

What is kinetic energy?

Answer 4

the energy of motion (associated with any kind of movement)

Question 5

What is potential energy?

Answer 5

stored energy (depends on structure of object or its position relative to a field)

Question 6

What are the 1st and 2nd laws of thermodynamics?

Answer 6

1st: Energy cannot be created nor destroyed, only transformed from one form to another

2nd: in any natural process, entropy either increases or remains constant but never decreases

Question 7

What is free energy?

Answer 7

free energy is the amount of energy available to do work (G)

Question 8

What is enthalpy?

Answer 8

total amount of energy in a system (H)

Question 9

What is entropy?

Answer 9

measure of disorder in a system (S)

Question 10

What is exergonic?

Answer 10

Releases energy

Question 11

How do free energy, enthalpy, entropy, exergonic, and endergonic all relate with each other?

Answer 11

Exergonic: negative free energy

Endergonic: positive free energy

enthalpy and entropy affect the overall amount of free energy

Question 12

What is the free energy equation? (standard and non-standard)

Answer 12

ΔG=ΔH−TΔS (standard)

ΔG=ΔGº +RTln[product/reactant] (non-standard/real world)

Question 13

Why can an endergonic reaction be “coupled” to an exergonic reaction?

Answer 13

The energy released by the exergonic reaction (negative ΔG) can be used to drive the endergonic reaction (positive ΔG), making the overall process favorable

ex: ATP hydrolysis

Question 14

What is a substrate?

Answer 14

“raw material” that an enzyme uses to create a product

Question 15

What is an active site?

Answer 15

a specific region on an enzyme where a substrate molecule binds and undergoes a chemical reaction

Question 16

What is activation energy?

Answer 16

the minimum amount of energy required for a chemical reaction to begin

Question 17

What is a transition state?

Answer 17

an unstable, high-energy intermediate state during a chemical reaction, representing the point where bonds are partially broken and formed

Question 18

How do the terms substrate, active site, activation energy, transition state, and reaction rate relate to each other?

Answer 18

When an enzyme binds to a substrate, it lowers the activation energy of the reaction by stabilizing the transition state thus allowing for a faster reaction rate

Question 19

Describe in general terms how enzymes can alter the rate of chemical reactions

Answer 19

• Enzymes function as a catalyst to accelerate the rate of a chemical reaction
• Although an enzyme accelerates a reaction by reducing the activation energy, the difference in free energy between reactants and products (ΔG) does not change

Question 19

Explain how small molecules (e.g., drugs or regulatory molecules) can increase or decrease the activity of an enzyme

Answer 19

• Activators increase the activity of an enzyme
• Inhibitors decrease the activity of an enzyme (they can occupy the active site), preventing the substrate from binding to the enzyme

Question 20

Predict whether a reaction will be exergonic or endergonic based on ΔH and ΔS

Answer 20

-ΔH & -ΔS = -ΔG at low T
-ΔH & +ΔS = -ΔG
+ΔH & +ΔS = ΔG at high T
+ΔH & -ΔS = ΔG

Question 21

How can you determine whether two reactions can be successfully coupled based on their changes in free energy?

Answer 21

See if they add up to a -ΔG, which means that the reaction will occur spontaneously

Question 22

Evaluate how changing cellular conditions will change the free energy of a reversible reaction

Answer 22

ΔG=ΔGº+RTlnQ

If Q is negative (more reactants than products), then ΔG decreases -> favorable in the forward direction

If Q is positive (more products than reactants), then ΔG increases -> favorable in the backward direction

Question 23

How do you interpret a graph for thermodynamic favorability?

Answer 23

Check if free energy (G) is negative

Question 24

How do you interpret a graph for the likelihood of coupling?

Answer 24

For the likelihood of coupling, add graphs together of endergonic and exergonic reactions and see if the change in G is negative; if negative, coupling will work.

Question 25

How do you interpret a graph to determine relative rates of reactions?

Answer 25

Higher activation energy hump = slower reaction Lower activation energy hump = faster reaction

Question 26

How do you interpret data to assess changes in enzyme function and predict the effects of regulatory molecules?

Answer 26

Must compare with control: - If enzyme rate is increased, an activator has been used. - If enzyme rate is decreased, an inhibitor has been used.

Question 27

Evaluate the effect of regulatory molecules on metabolic pathways

Answer 27

Allosteric enzymes are enzymes that are regulated by molecules that bind at sites other than their active sites and can be influenced by inhibitors and activators Helps with ensuring metabolic control and homeostasis by turning pathways on and off in response to cellular signals

Question 28

Relate the pH scale to the concentration of hydrogen ions in a solution

Answer 28

The more hydrogen ions there are, the more acidic a solution is (pH gets lower than 7)

Question 29

How do environmental effects like pH and temperature affect enzyme-catalyzed reaction rates?

Answer 29

As temperature increases, the reaction rate increases, but if the temperature passes the optimal range, the enzyme will stop functioning. Each enzyme has a specific pH. If it is exposed to a different pH, the enzyme's activity will slow down or stop.

Question 30

Relate anabolic and catabolic pathways to overall changes in free energy

Answer 30

Anabolic pathways require an input of energy, resulting in a positive change in free energy (endergonic), while catabolic pathways release energy, resulting in a negative change in free energy (exergonic).

Question 31

Interpret free energy diagrams to predict the free energy changes involved in a reaction, the kinetics of a reaction, and the impact of adding an enzyme to a reaction

Answer 31

Reactants vs. Products: Height difference = ΔG ΔG < 0 → reaction is spontaneous ΔG > 0 → reaction is non-spontaneous Activation Energy (Ea): Height from reactants to transition state Higher Ea = slower reaction Lower Ea = faster reaction Effect of Enzyme: Lowers Ea (activation energy) Does NOT change ΔG Speeds up the reaction without changing its favorability

Question 32

Interpret enzyme kinetics graphs to determine the relative rate of an enzyme-catalyzed reaction under different reaction conditions.

Answer 32

If an enzyme is inhibited, it will have a higher activation energy If an enzyme is activated, it will have a lower activation energy