Biochemistry: Enzyme Activity and Free Energy

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Questions and Answers

What does the First Law of Thermodynamics state?

Energy can only increase over time.

Energy is conserved and can change form. (correct)

Energy transformations are 100% efficient.

Energy can be created and destroyed.

Which law states that the entropy of the Universe is always increasing?

Second Law of Thermodynamics (correct)

Zeroth Law of Thermodynamics

First Law of Thermodynamics

Third Law of Thermodynamics

Which process primarily provides energy for most living organisms?

Solar energy (correct)

Nuclear energy

Geothermal energy

Chemical energy from the Earth

What occurs to entropy as a system's temperature approaches absolute zero?

Entropy approaches a minimum value. Signup and view all the answers

What is the role of redox reactions in living cells?

To drive energy transductions. Signup and view all the answers

Which one of the following statements best describes potential energy in biological systems?

It can come from sunlight and nutrients. Signup and view all the answers

In the context of bioenergetics, which type of work is related to chemical synthesis?

Chemical work Signup and view all the answers

What is a characteristic of perpetual motion machines according to the First Law of Thermodynamics?

They are impossible to achieve. Signup and view all the answers

Which law of thermodynamics is related to the thermal equilibrium of systems?

Zeroth Law of Thermodynamics Signup and view all the answers

What is the main product of respiration in living organisms?

Heat and energy Signup and view all the answers

What does a negative change in Gibbs Free Energy (DG) indicate about a reaction?

The reaction is spontaneous. Signup and view all the answers

If the change in enthalpy (DH) is greater than the product of temperature (T) and the change in entropy (DS), what can be concluded about DG?

DG is positive, indicating non-spontaneity. Signup and view all the answers

What is the standard condition for Gibbs Free Energy change (DG0) in a biochemical reaction?

Temperature at 25°C and 1.00 M concentration for all reactants. Signup and view all the answers

In the equation DG = DH - TDS, what does DS represent?

Change in entropy. Signup and view all the answers

Which statement describes a condition that makes DG0 less useful in biochemical contexts?

It assumes all reactants are at 1.00 M concentration, including H+. Signup and view all the answers

What modification can be made to the Gibbs Free Energy equation to account for concentrations in non-equilibrium conditions?

Incorporate K, the equilibrium constant, into the equation. Signup and view all the answers

How does the presence of H+ affect the calculation of DG0 in biochemical processes?

H+ concentrations can vary widely, complicating DG0 calculations. Signup and view all the answers

What units are used for the change in Gibbs Free Energy (DG)?

J/mol Signup and view all the answers

What is the significance of DG in the hydrolysis of ATP in skeletal muscle?

It indicates the amount of energy released during ATP hydrolysis. Signup and view all the answers

How does the concentration of ATP, ADP, and Pi affect the Gibbs Free Energy (DG) in different tissues?

Variations in these concentrations lead to differing values of DG. Signup and view all the answers

What does a DG value that is 76% greater than DG0’ indicate in the context of ATP hydrolysis?

The energy available from ATP hydrolysis is significantly increased. Signup and view all the answers

What is the role of glucokinase in ATP hydrolysis?

It catalyzes the phosphorylation of glucose to glucose-6-phosphate using ATP. Signup and view all the answers

What happens to the rate constant (k) according to the equation k = A e(-DGactivation / RT)?

It decreases as DGactivation increases. Signup and view all the answers

In the hydrolysis of ATP, what are the products formed?

ADP and inorganic phosphate (Pi). Signup and view all the answers

What would be an expected consequence of decreasing ATP concentration in a muscle cell?

Decreased energy available for biochemical reactions. Signup and view all the answers

What is the function of the ideal gas constant R in the rate constant equation?

It relates the rate constant to temperature and activation energy. Signup and view all the answers

When ATP splits into ADP and Pi, what type of reaction is taking place?

Hydrolysis reaction. Signup and view all the answers

What does the term 'activation energy' refer to in the context of biochemical reactions?

The energy needed to break bonds in reactants before forming products. Signup and view all the answers

What is the primary function of ATP in the cell?

To serve as a major energy currency Signup and view all the answers

Which of the following correctly describes the process of polymerization in cells?

It decreases the entropy of the cell. Signup and view all the answers

How is free energy related to biochemical reactions?

It measures the energy available for work in biochemical reactions. Signup and view all the answers

What role do sodium-potassium ATPase pumps play in the cell?

They maintain ion gradients across the cell membrane. Signup and view all the answers

Which statement is true regarding ion gradients in the cell?

They drive functions such as muscular and neuronal activity. Signup and view all the answers

What is a characteristic feature of the electron transport chain in mitochondria?

It helps in ATP synthesis through proton gradients. Signup and view all the answers

What is the significance of the equilibrium constant (K) in biochemical reactions?

It shows the relationship between forward and backward reaction rates. Signup and view all the answers

What effect does entropy have when monomers polymerize into macromolecules?

It decreases the entropy of the cell. Signup and view all the answers

In what way do proton gradients influence cellular functions?

They are essential for driving active transport mechanisms. Signup and view all the answers

Which of the following statements correctly relates free energy and biochemical reactions?

Free energy measurement determines the spontaneity of reactions. Signup and view all the answers

At what pH do most enzymes become inactive?

pH = 0 Signup and view all the answers

What is DG0’ defined as?

The change in free energy at all conditions standardized to pH 7 Signup and view all the answers

What does the equation DG = DG0’ + RT ln([B]p/[A]p) represent?

The relationship between free energy and concentration at any pH Signup and view all the answers

What can allow a reaction with a positive DG0’ to proceed?

A negative steady-state ratio of products to reactants Signup and view all the answers

What is the DG0’ value of hydrolyzing the red bond associated with ATP?

-31 kJ mol-1 refers to 1.0 M concentration Signup and view all the answers

What are the typical concentrations of ATP in living cells?

[ATP] = 8.5 mM Signup and view all the answers

What does the term 'steady-state ratio' refer to in biochemical reactions?

The ratio of products to substrates under dynamic equilibrium Signup and view all the answers

Which of the following components is NOT involved in the hydrolysis reaction of ATP?

Glucose Signup and view all the answers

Study Notes

Enzymatic Activity and Free Energy

Enzymes are generally inactive at pH 0.
DG0’ represents the change in free energy at standard conditions, specifically at pH 7.00.
The relationship for free energy at pH 7 is expressed as:
- DG0’ = - RT ln(K)
- DG = DG0’ + RT ln([B]p/[A]p)
A positive DG0’ may still result in a negative DG if the ratio of products to reactants is favorable.

Biochemical Energy

Key molecules include:
- Phosphate (Pi)
- Adenosine diphosphate (ADP)
- Adenosine triphosphate (ATP)
The standard DG0’ for hydrolyzing ATP (red bond) is -31 kJ/mol at 1.0 M concentration of reactants/products.
Actual cellular concentrations in frog skeletal muscle:
- [ATP] = 8.5 mM
- [ADP] = 0.25 mM
- [Pi] = 2.6 mM
Water concentration remains essentially constant in biochemical calculations.

Gibbs Free Energy and Cellular Reactions

The equation governing ATP hydrolysis in context is:
- DG = DG0’ + RT ln([ADP][Pi]/[ATP])
Calculated DG for ATP hydrolysis in skeletal muscle approximates -55 kJ/mol.
The true free energy change for ATP hydrolysis can be about 76% greater than DG0’.

Glucokinase and Reaction Coordination

Glucokinase catalyzes the conversion of glucose to glucose-6-phosphate using ATP, with reactions dependent on Gibbs Free Energy.
The overall DG for the system combines individual reaction energies:
- DGoverall = DG1 + DG2

Activation Energy and Reaction Rates

The rate of reaction can be described by:
- k = A e^(-DGactivation / RT)
Where:
- k = rate constant
- A = pre-exponential factor
- R = gas constant
- T = temperature (K)

Thermodynamics in Bioenergetics

The first law states energy cannot be created or destroyed, only transformed.
The second law posits that physical and chemical changes promote increasing disorder (entropy).
The third law relates to the approach of entropy toward a minimum value at absolute zero.
The zeroth law emphasizes the thermal equilibrium necessary for temperature measurements.

Energy Dynamics in Living Organisms

Living cells function as chemical engines at constant temperature, deriving energy primarily from solar sources.
Redox reactions are essential for energy transduction in cells.
Organisms exchange energy with their environment, impacting whole ecosystems.

Potential Energy and Metabolic Processes

Energy sources include sunlight and nutrients.
Cells perform chemical transformations to synthesize macromolecules, driving cellular functions.
Metabolic by-products include simpler compounds, contributing to increased entropy.

Mitochondrial Function and ATP Synthesis

The mitochondrial electron transport chain facilitates ATP production from ADP and Pi through oxidative phosphorylation.
Proton gradients generated during respiration are vital for ATP synthesis and various cellular processes.

Understanding Free Energy and Thermodynamics

Free energy is the energy available for work, distinct from enthalpy.
The Gibbs Free Energy equation connects changes in Gibbs Free Energy (DG) to enthalpy (DH) and entropy (DS):
- DG = DH - TDS
The sign of DG indicates reaction spontaneity: positive (non-spontaneous), negative (spontaneous), or zero (equilibrium).

Standard Free Energy Change (DG0)

Standard conditions for DG0 include 1.00 M concentration of all reactants/products and stay consistent at 25°C.
DG0 is not very applicable in biochemistry where pH levels are critical, particularly involving H+ ions.

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Description

Explore key concepts in biochemistry related to enzymatic activity, pH influence on enzymes, and the thermodynamics of biochemical reactions. This quiz covers the significance of DG0’ and free energy changes at standard conditions. Test your understanding of how enzymes function under varying pH levels.