Enzymes and Metabolism

What is metabolism in living organisms?

Metabolism is the set of biochemical reactions and energy processes that keep organisms alive.

What does the First Law of Thermodynamics state?

Energy cannot be created or destroyed, only converted.

What does the Second Law of Thermodynamics state?

Energy transfers increase entropy (disorder) in a system.

What is the role of mitochondria in metabolism?

Mitochondria convert energy from organic compounds into ATP but do not create energy.

What does ATP stand for, and why is it important?

ATP stands for Adenosine Triphosphate. It is the main energy currency of the cell.

What is Gibbs Free Energy (G)?

It is the energy available in a cell to do work, factoring in entropy.

How does Gibbs Free Energy determine reaction spontaneity?

• Negative ΔG: Reaction releases energy (exergonic, spontaneous).

• Positive ΔG: Reaction absorbs energy (endergonic, not spontaneous).

What is an exergonic reaction?

A reaction that releases energy and has a negative ΔG.

Give an example of an exergonic reaction.

Breaking down sucrose into glucose and fructose.

What is an endergonic reaction?

A reaction that absorbs energy and has a positive ΔG.

Give an example of an endergonic reaction.

Forming sucrose from glucose and fructose.

Can spontaneous reactions happen slowly?

Yes, even if a reaction is spontaneous, it may still take a long time without an enzyme.

What is the key takeaway about metabolism and energy?

Metabolism is essential for life and follows the laws of thermodynamics.

What are the two types of metabolic pathways?

Catabolic (breaks down molecules, releases energy) and Anabolic (builds molecules, requires energy).

What is the primary function of enzymes in metabolism?

Speed up chemical reactions by lowering activation energy.

What happens when ATP releases a phosphate group?

It becomes ADP (Adenosine Diphosphate) and releases energy.

What does a cell use energy for?

Movement, active transport, and chemical reactions.

What is the difference between a spontaneous and a non-spontaneous reaction?

Spontaneous releases energy (exergonic); non-spontaneous requires energy (endergonic).

What is the role of cellular respiration?

Convert glucose energy into ATP for cell use.

What is enzyme saturation?

When all active sites of an enzyme are occupied by substrate.

Why are metabolic pathways regulated?

To avoid overproduction or depletion of materials.

What happens in a coupled reaction?

An exergonic reaction provides energy for an endergonic reaction.

What is the transition state in a chemical reaction?

The point where reactants are unstable and ready to be converted into products.

What is the lock and key model of enzymes?

Substrate fits exactly into the enzyme's active site like a key in a lock.

How does temperature affect enzyme activity?

Higher temperatures can denature enzymes; low temperatures slow reactions.

What happens when an enzyme is denatured?

It loses its shape and no longer functions.

What is the main function of coenzymes in enzyme activity?

Assist enzymes in catalyzing reactions.

What type of inhibition is irreversible?

When an inhibitor forms a covalent bond with the enzyme.

What is enzyme cooperativity?

When binding one substrate increases enzyme's affinity for more substrates.

What is the purpose of phosphorylation in energy transfer?

Adding a phosphate group to a molecule to activate it.

Why does the body break down glucose gradually instead of all at once?

To capture energy in small, usable amounts without damaging the cell.

What is the purpose of NAD+ in metabolism?

It acts as an electron carrier during cellular respiration.

Why are metabolic pathways irreversible?

Large energy changes make it difficult to reverse the reactions.

What is the difference between competitive and noncompetitive enzyme inhibitors?

Competitive Inhibitors bind to the active site, blocking the substrate.
Noncompetitive Inhibitors bind to a different site (allosteric site), changing the enzyme’s shape so the substrate can’t bind.

What is allosteric inhibition?

A molecule binds to an allosteric site, changing the enzyme's shape and reducing its activity.

How does enzyme activation work?

An activator binds to an allosteric site, stabilizing the enzyme in its active form, making it more efficient.