Week 5 Application Questions Flashcards
Part A: What is energy?
1. Electron position is related to potential energy, e.g. if a molecule is oxidized an electron is lost and energy is released.
a. In a redox system which reaction is endergonic and which reaction is exergonic?
(Oxidation = loss of e)
- Exergonic
(Reduced = gain of e)
- Endergonic
Part A: What is energy?
1. Electron position is related to potential energy, e.g. if a molecule is oxidized an electron is lost and energy is released.
b. Which of the following bonds has the highest potential energy and which bond has the lowest potential energy? N-H, O-H, C-C,
Highest = C-C
Middle = N-H
Lowest = O-H
Part A: What is energy?
1. Electron position is related to potential energy, e.g. if a molecule is oxidized an electron is lost and energy is released.
c. You have 10 g of butter (containing mostly saturated fats) and 10 g of table sugar (sucrose).
Using your understanding of the energy stored in covalent bonds, predict which of these two would contain more total calories (i.e. stored energy). Explain the reason for your choice.
It’s butter
Butter (saturated fat):
Lots of non-polar bonds = high energy
Table sugar (sucrose): Lots of polar bonds
= lower energy
Part A: What is energy?
2. The 2nd law of thermodynamics states that energy transformations increase entropy, but living things are very ordered and non-random.
Explain how living things can exist without violating the second law of thermodynamics.
– Cells are open systems
– Take in energy and matter in low entropy forms (highly ordered)
→ used to create localized order in the cell
– Energy and matter are returned to surroundings in a less ordered form
→ Organisms decrease order of their surroundings and increase their own
Part B: What are enzymes?
3. The question below deals with the enzyme invertase. Invertase catalyzes the following chemical reaction:
Sucrose + H2O → Glucose + Fructose
a. Is this reaction endergonic or exergonic? Explain how you can tell.
b. Based on your answer in part (a), would this reaction have a positive or a negative ΔG?
c. Is this a dehydration or a hydrolysis reaction?
d. Is this reaction part of a catabolic or an anabolic process?
e. Do the products or the reactants in this reaction have a higher amount of entropy?
This is a Hydrolysis reaction
- Breaks bonds between monomers = catabolic process
- Uses a water molecule (+ H2O on left side)
- Releases energy, increases entropy
This reaction increases entropy,
- releases energy, is exergonic because it
has a Negative ΔG
- the products have a higher entropy than reactants.
Part B: What are enzymes?
3. The question below deals with the enzyme invertase. Invertase catalyzes the following chemical reaction:
Sucrose + H2O → Glucose + Fructose
f. Describe in detail how the invertase enzyme would function in this chemical reaction.
• Step 1: Entering Enzyme Active Site (where substrate binds to enzyme)
– Shape allows only correct substrate to fit
– Side chains of amino acids in active site form non-covalent bonds with correct substrate
— H-bonds
— Ionicbonds
— Hydrophobic interactions
• Step 2: Enzyme/substrate complex forms.
- enzyme changes shape slightly as substrate binds = induced fit.
• Step 3: Reduces activation energy.
- Stresses old bonds = easier to break
- Lines up substrates to form new bonds
- Creates favourable charge environment for reaction
- Substrate is converted to products.
• Step 4: Products leave the active site of the enzyme.
- Reduced fit
Part B: What are enzymes?
3. The question below deals with the enzyme invertase. Invertase catalyzes the following chemical reaction:
Sucrose + H2O → Glucose + Fructose
g. Explain why heating up the cell would not be a successful strategy to allow this reaction to occur without the invertase enzyme.
• Without an enzyme, a lot of activation energy is needed,
• Heat could provide EA, but
– The amount of heat needed
would kill the cell:
– Denature DNA and proteins
– Disrupt the cell membrane
– Heat would speed up all the chemical reactions in the cell at once, not just the ones needed by the cell
Part B: What are enzymes?
3. The question below deals with the enzyme invertase. Invertase catalyzes the following chemical reaction:
Sucrose + H2O → Glucose + Fructose
h. Draw a graph that plots the change in the amount of free energy as the reaction progresses from reactant (sucrose, before the reaction) to products (glucose and fructose, after the reaction) in the presence and the absence of enzyme (invertase).
For both, indicate the change in free energy ( G) between reactants and products and the activation energy (EA). Your y-axis should be free energy (G) and your x-axis time or the progress of the reaction.
Part B: What are enzymes?
4. ATPases are enzymes that catalyze hydrolysis of ATP. Typically, these hydrolysis reactions are coupled to another cellular process that requires energy
a. Identify a cellular process that is normally powered by hydrolysis of ATP.
– Active transport
– Movement
– Chemical reactions
• Energy is transferred by phosphorylation (transfer of phosphate group)
• hydrolysis reaction is exergonic
Unstable bonds = high free energy (ATP)
+ H2O
—>
Fewer unstable bonds = lower free energy (ADP)
Part B: What are enzymes?
4. ATPases are enzymes that catalyze hydrolysis of ATP. Typically, these hydrolysis reactions are coupled to another cellular process that requires energy
b. Imagine that you introduced into a cell a genetically-engineered ATPase enzyme that was not coupled to any cellular process, and instead hydrolyzed ATP without doing any work (= energy transferred by mechanical means, or force x displacement).
Describe the effects you might expect to observe in a cell containing this engineered enzyme
ATP -> ADP+ P + free energy
Increase of Pi and increase in heat (unorganized energy)
Eventually you’d see metabolic processes stop b/c cell isn’t replenishing the molecules it needs in order to keep producing ATP
Part B: What are enzymes?
5. Go to the following website and read about the use of enzymes in laundry detergents:
https://www.aboutcleaningproducts.com/science/ezyme-science/
a. The enzymes added to laundry detergent are typically a mixture of several different types of enzymes, including proteases, amylases, lipases, and cellulases.
Explain why a good laundry detergent would need a mix of these enzymes, rather than just including a single type of enzyme
• Food stains on clothes contain lots of different molecules
• Enzymes are specific to one substrate because of active site
• Needs lots of different enzymes because you have lots of different kinds of molecules to break down
Part B: What are enzymes?
5. Go to the following website and read about the use of enzymes in laundry detergents:
https://www.aboutcleaningproducts.com/science/ezyme-science/
b. Some people add baking soda (which is basic) or vinegar (which is acidic) to their laundry loads.
Explain why this addition might alter the effectiveness of the enzymes in the laundry detergent.
• Enzymes have an optimal pH
• pH can change charges on amino acid
side chains
• Will affect bonding in tertiary structure
• Can change shape of enzyme active site and make enzyme less active
