BIO13 Week 4 Comprehension Worksheet

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Questions and Answers

What does the first law of thermodynamics state?

Energy can be created but not destroyed.

Energy can only change forms or be transferred. (correct)

Energy cannot change forms or be transferred.

Energy is always lost as heat in reactions.

Which of the following best describes kinetic energy?

Energy stored in water molecules.

Energy held in electrical gradients.

Energy of movement or motion. (correct)

Energy stored in chemical bonds.

Which type of energy is associated with the potential to form stronger bonds?

Potential energy (correct)

Kinetic energy

Thermal energy

Gravitational energy

Why do longer, weaker bonds contain more potential chemical energy?

They can easily form stronger bonds. Signup and view all the answers

Which molecule is likely to have higher potential energy under normal conditions?

Methane (CH4) Signup and view all the answers

Why do fats provide more calories per gram than proteins or carbohydrates?

Fats consist of more hydrocarbon bonds. Signup and view all the answers

How does ATP function as an energy molecule in cells?

By transferring energy through its phosphate groups. Signup and view all the answers

What happens to the potential energy of the sodium gradient when a neuron is activated?

It decreases, as ions passively move into the cell. Signup and view all the answers

In biological systems, energy must come from where when reactions require energy?

It is absorbed from the surroundings. Signup and view all the answers

Which statement best describes the law of conservation of mass?

Mass can be transformed but not created or destroyed. Signup and view all the answers

When a reversible reaction is at equilibrium, what can be concluded about the concentrations of reactants and products?

The concentrations have reached a stable ratio but are not necessarily equal. Signup and view all the answers

How does an increase in pH affect the ionization of a basic functional group?

It decreases the likelihood of finding the group in its ionized state. Signup and view all the answers

What effect does a decrease in pH have on the ionization of an acidic functional group?

It leads to a shift of equilibrium to the left, favoring the protonated form. Signup and view all the answers

Which of the following is true about the concentrations of reactants and products during a chemical equilibrium?

They remain constant over time. Signup and view all the answers

What is the impact of an increased pH on the likelihood of a functional group being protonated?

It decreases the likelihood as fewer protons are available. Signup and view all the answers

In the context of ionized states, how does an increase in pH relate to acidic functional groups?

Acidic functional groups are more likely to lose protons. Signup and view all the answers

Which functional group is classified as basic within the biological range of pH values?

Amide Signup and view all the answers

At a pH of 4, what happens to the proportion of non-ionized hydroxyl groups?

Increases as a percentage of the whole Signup and view all the answers

What characterizes a spontaneous reaction regarding Gibbs free energy?

Gibbs free energy is less than zero Signup and view all the answers

Which of the following functional groups is stable and neither classified as an acid nor a base at biological pH?

Carbonyl Signup and view all the answers

What happens during nonspontaneous reactions in terms of energy?

Energy is absorbed from the surroundings Signup and view all the answers

Which statement about enthalpy and Gibbs free energy is correct?

Enthalpy is the total energy in a molecule Signup and view all the answers

Which functional groups are generally classified as acidic within biological pH ranges?

Carboxyl and phosphate Signup and view all the answers

What effect does a decrease in pH have on the chemical equilibrium of hydrolysis of hydroxyl groups?

It shifts the equilibrium to produce more -O- and H+ Signup and view all the answers

What characterizes a reaction where Δ(G) < 0?

The reaction is exergonic. Signup and view all the answers

In a redox reaction involving NAD converting to NADH, what happens to NAD?

NAD is reduced. Signup and view all the answers

Which of the following best describes beta-mercaptoethanol's role as a reducing agent?

It donates electrons to a disulfide bond, which is then broken. Signup and view all the answers

Which molecule in the reaction CH4 + 2O2 → CO2 + 2H2O is being oxidized?

Methane (CH4) Signup and view all the answers

How does ATP facilitate nonspontaneous reactions?

By hydrolyzing its terminal phosphate group. Signup and view all the answers

What is the primary reason that ATP has high potential energy?

It has three negatively charged phosphate groups. Signup and view all the answers

Which descriptor applies to reduction reactions?

They always occur alongside oxidation reactions. Signup and view all the answers

What happens to the free energy of reactants during an endergonic reaction when ATP is used?

It increases as ATP becomes a reactant. Signup and view all the answers

What is a key difference between the induced-fit model and the lock-and-key model?

The induced-fit model allows for flexibility in enzyme shape during binding. Signup and view all the answers

Which analogy best describes the induced-fit model of enzyme activity?

A glove that adjusts to the shape of a baseball. Signup and view all the answers

When designing a drug to inhibit the HIV protease enzyme, what characteristic should the drug molecule possess?

It should be hydrophobic to fit into the active site. Signup and view all the answers

The action of a drug successfully blocking the active site of the HIV enzyme protease is an example of what?

Competitive inhibition. Signup and view all the answers

Which model suggests that enzymes can alter their shape upon substrate binding?

Induced-fit model. Signup and view all the answers

What is the role of activation energy in biological reactions?

It is the energy required to start a reaction regardless of enzyme presence. Signup and view all the answers

How does an increase in entropy affect Gibbs free energy in a reaction?

It can contribute to a negative change in Gibbs free energy. Signup and view all the answers

Which of the following statements is true regarding Gibb's free energy?

It indicates the spontaneity of a reaction. Signup and view all the answers

Study Notes

Thermodynamics in Biology

The first law of thermodynamics states energy can be transformed or transferred but not created or destroyed.
In biological reactions, energy must come from external sources or is released as heat.
Kinetic energy is energy of movement, seen in heat and protein shape changes, whereas potential energy is stored in bonds, charges, and gradients.
Longer and weaker bonds have higher potential energy due to the ability to form stronger bonds.
Fats have higher caloric value due to more hydrocarbon/nonpolar bonds than carbohydrates or proteins.
ATP serves as a primary energy molecule, storing energy through the clustering of negatively charged phosphate groups.
When neurons activate, the concentration gradient's potential energy decreases as sodium ions (Na+) enter the cell.

Chemical Equilibrium

The law of conservation of mass asserts that mass cannot be created or destroyed; all atoms must balance in a chemical equation.
At equilibrium in a reversible reaction, concentrations of reactants do not have to be equal, but their ratios remain constant.
Increased pH decreases hydrogen ion concentration, shifting equilibria to un-ionized states for acidic functional groups.
Functional group classifications: amide and amine are basic; carboxyl, hydroxyl, and phosphate are acidic; carbonyl is neutral.
At lower pH, hydroxyl groups may shift towards non-ionized states due to higher concentrations of H+ ions.

Gibb's Free Energy

Spontaneous reactions have a negative change in Gibb’s free energy (ΔG < 0), indicating favorable energy dynamics.
Nonspontaneous reactions need energy input (ΔG > 0) to occur.
Enthalpy (H) refers to total energy; negative changes indicate exothermic reactions, while positive suggest endothermic processes.
Entropy (S) measures disorder; favorable entropy increases overall reaction spontaneity.

Redox Reactions

NAD is reduced to NADH during electron transfer.
Reduction reactions are typically endergonic while oxidation reactions are exergonic.
Beta-mercaptoethanol acts as a reducing agent by donating electrons and protons to disulfide bonds, reducing the bond.
In methane combustion (CH4 + 2O2 → CO2 + 2H2O), methane is oxidized and oxygen is reduced.
CH4 has the highest potential energy due to weak nonpolar bonds.

ATP and Energy Transfer

ATP stores energy in its three phosphate groups due to repulsion among negatively charged groups.
Hydrolysis of ATP's terminal phosphate releases energy used for driving nonspontaneous reactions.
ATP can convert endergonic reactions to exergonic by increasing reactants' free energy.
The induced-fit model explains enzyme-substrate interactions where the enzyme shape adjusts upon binding, contrasting with the rigid lock-and-key model.

Enzyme Inhibition

For designing competitive inhibitors for the HIV enzyme protease, the drug should mimic the hydrophobic environment of the enzyme's active site.

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Description

This quiz focuses on comprehension topics from BIO13, particularly from Chapter 2, Section 2.3, which deals with chemical reactions and energy related to biological systems. Students will answer lower order and higher order questions to reinforce their understanding of biological energy. Prepare by watching the associated video on types of biological energy.