unit 4 - reactions and enzymes
24. define the following terms:
a. enzyme

b. catalyst

c. activation energy

use the energy diagram to answer questions 25 and 26.
25. does the energy diagram represent an endergonic or
exergonic reaction?
how can you tell?

26. how would the energy diagram change if a catalyst
was added to the reaction?

27. label the diagram below with the following words: enzyme, substrate, active site,
and product.
a.

b.

c.

d.

28. describe what is happening in each step of the diagram above.
a. step 1

b. step 2

c. step 3

29. what three factors affect the function of an enzyme by changing its shape?

Question

unit 4 - reactions and enzymes
24. define the following terms:
    a. enzyme

b. catalyst

c. activation energy

use the energy diagram to answer questions 25 and 26.
25. does the energy diagram represent an endergonic or
exergonic reaction?
how can you tell?

26. how would the energy diagram change if a catalyst
was added to the reaction?

27. label the diagram below with the following words: enzyme, substrate, active site,
and product.
a.

b.

c.

d.

28. describe what is happening in each step of the diagram above.
    a. step 1

b. step 2

c. step 3

29. what three factors affect the function of an enzyme by changing its shape?

Accepted Answer

### Question 24
#### a. Enzyme
# Brief Explanations:
An enzyme is a biological catalyst, typically a protein (or sometimes RNA), that speeds up chemical reactions in living organisms by lowering the activation energy required for the reaction to occur. It is highly specific to its substrate (the molecule it acts on) and functions within a particular range of temperature and pH.
# Answer:
A biological catalyst (usually a protein or RNA) that speeds up chemical reactions in cells by lowering activation energy, specific to its substrate.

#### b. Catalyst
# Brief Explanations:
A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It works by lowering the activation energy of the reaction, allowing the reaction to proceed more quickly. Catalysts can be inorganic (like metals) or organic (like enzymes in biological systems).
# Answer:
A substance that increases the rate of a chemical reaction without being consumed, by lowering activation energy.

#### c. Activation Energy
# Brief Explanations:
Activation energy is the minimum amount of energy that reactant molecules must possess in order to undergo a chemical reaction. It is the energy barrier that must be overcome for the reaction to start. Catalysts (including enzymes) function by reducing this energy barrier.
# Answer:
The minimum energy reactant molecules need to undergo a chemical reaction (the energy barrier to start the reaction).

### Question 25
# Brief Explanations:
To determine if a reaction is endergonic or exergonic, we compare the free energy of the reactants (A) and the products (D). In an exergonic reaction, the products have less free energy than the reactants, meaning energy is released. In an endergonic reaction, products have more free energy (energy is absorbed). From the diagram, the free energy of D (products) is lower than A (reactants), so energy is released.
# Answer:
- Reaction type: Exergonic.
- Reason: The free energy of the products (D) is lower than the free energy of the reactants (A), so energy is released during the reaction.

### Question 26
# Brief Explanations:
A catalyst (like an enzyme) works by lowering the activation energy of a reaction. The activation energy is represented by the height of the energy "hill" (the peak between reactants and products). When a catalyst is added, it reduces this activation energy, so the height of the peak (the energy barrier) in the energy diagram will decrease. The free energy of the reactants and products remains unchanged, only the activation energy (the energy needed to start the reaction) is lowered.
# Answer:
Adding a catalyst (like an enzyme) would lower the activation energy of the reaction. This means the height of the energy peak (the activation energy barrier) in the diagram would decrease. The free energy of the reactants (A) and products (D) would remain the same, but the reaction would proceed more quickly because less energy is needed to start it.

### Question 27
# Brief Explanations:
- **Enzyme**: The enzyme is the larger, relatively unchanging molecule (the "lock" in the lock - and - key model) that provides the active site. In the diagram, the larger, rounded structure (C and the ones in Step 2 and Step 3) is the enzyme, as it remains after the reaction and is involved in binding the substrate.
- **Substrate**: The substrate is the molecule (or molecules) that bind to the enzyme's active site. In Step 1, the smaller molecules (A) that are about to bind to the enzyme are the substrates.
- **Active Site**: The active site is the specific region on the enzyme where the substrate binds. In Step 1, the indentation or specific area on the enzyme (B) where the substrate will bind is the active site.
- **Product**: The products are the molecules formed after the enzyme - catalyzed reaction. In Step 3, the smaller molecules (D) that are released from the enzyme are the products, as they are the result of the reaction on the substrate.

So:
- A: Substrate (the molecules that bind to the enzyme)
- B: Active Site (the region on the enzyme where substrate binds)
- C: Enzyme (the larger molecule that catalyzes the reaction, remains after)
- D: Product (the molecules formed and released after the reaction)
# Answer:
- A: Substrate
- B: Active Site
- C: Enzyme
- D: Product

### Question 28
#### a. Step 1
# Brief Explanations:
In Step 1, the substrate molecules (A) are approaching the enzyme (C) and are about to bind to the enzyme's active site (B). This is the initial step of the enzyme - catalyzed reaction where the substrate and enzyme come together, with the substrate fitting into the enzyme's active site (like a key into a lock in the lock - and - key model).
# Answer:
In Step 1, the substrate molecules (A) bind to the active site (B) of the enzyme (C). The enzyme and substrate form an enzyme - substrate complex as the substrate fits into the enzyme's active site.

#### b. Step 2
# Brief Explanations:
Step 2 shows the enzyme - substrate complex. The enzyme is catalyzing the reaction on the substrate. During this step, the chemical reaction occurs: the substrate is being converted into the product(s) while still bound to the enzyme's active site. The enzyme is facilitating the reaction, and the substrate is in the process of being transformed.
# Answer:
In Step 2, the enzyme - substrate complex is formed, and the enzyme is catalyzing the chemical reaction of the substrate. The substrate is being converted into the product(s) while bound to the enzyme's active site.

#### c. Step 3
# Brief Explanations:
In Step 3, the reaction is complete. The product(s) (D) have been formed and are being released from the enzyme's active site. The enzyme (C) remains unchanged and is now free to bind to new substrate molecules and catalyze another reaction.
# Answer:
In Step 3, the product(s) (D) are released from the enzyme's active site. The enzyme (C) is now free to bind to new substrate molecules and repeat the catalytic process.

### Question 29
# Brief Explanations:
Three factors that affect enzyme function by changing its shape (causing denaturation or altering the active site) are:
1. **Temperature**: High temperatures (above the enzyme's optimal temperature) can break the weak bonds (like hydrogen bonds) that maintain the enzyme's three - dimensional structure, including the active site. Low temperatures can also reduce enzyme activity, but high temperatures often cause permanent denaturation.
2. **pH**: Each enzyme has an optimal pH range. Deviating from this range (either too acidic or too basic) can disrupt the ionic and hydrogen bonds in the enzyme, changing the shape of the active site. For example, pepsin (in the stomach) works best at acidic pH, while trypsin (in the small intestine) works best at a more neutral to basic pH.
3. **Concentration of certain chemicals (like inhibitors)**: Some inhibitors can bind to the enzyme and change its shape. Competitive inhibitors bind to the active site, but non - competitive inhibitors bind to another site (allosteric site) and cause a conformational change in the enzyme, altering the active site's shape so that the substrate can no longer bind effectively.
# Answer:
Three factors that affect enzyme function by changing its shape are:
1. Temperature (extreme temperatures can denature the enzyme, altering the active site shape).
2. pH (deviating from the enzyme's optimal pH can disrupt bonds and change the active site shape).
3. Presence of inhibitors (e.g., non - competitive inhibitors bind to allosteric sites and cause conformational changes in the enzyme, altering the active site).

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QUESTION IMAGE

Question

Explanation:

Question 24

a. Enzyme

Answer:

b. Catalyst