Energy and Enzymes Overview

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Questions and Answers

What does the First Law of Thermodynamics state about energy?

Energy transformations do not affect the organization of matter.

Energy can be created and destroyed.

Energy can only be transferred, not created or destroyed. (correct)

Energy can be created from matter in biological systems.

What is true about spontaneous reactions according to the principles of thermodynamics?

They always involve an increase in free energy.

They must decrease the entropy of the universe.

They have ΔG < 0. (correct)

They are characterized by a positive ΔG.

Which of the following correctly differentiates catabolism from anabolism?

Catabolism and anabolism are identical processes with different names.

Only catabolism requires energy input.

Catabolism synthesizes complex molecules; anabolism breaks down molecules.

Catabolism releases energy; anabolism consumes energy. (correct)

What role does ATP play in metabolism?

ATP acts as the primary energy currency that couples catabolic and anabolic reactions. Signup and view all the answers

In which process does free energy decrease?

Exergonic reactions. Signup and view all the answers

What happens to entropy during every energy transformation?

Entropy increases, contributing to disorder in the universe. Signup and view all the answers

Which statement about free energy (ΔG) is accurate?

Lower ΔG in products compared to reactants indicates spontaneous reactions. Signup and view all the answers

How do organisms maintain their high level of organization according to energy principles?

By utilizing continuous energy inputs to counteract entropy. Signup and view all the answers

Which of the following is a correct statement regarding exergonic and endergonic reactions?

Exergonic reactions are spontaneous; endergonic reactions are not. Signup and view all the answers

What type of metabolic pathway is characterized by breaking down complex molecules to release energy?

Catabolism Signup and view all the answers

What is the primary effect of ATP hydrolysis in biochemical reactions?

It causes a conformational change in proteins. Signup and view all the answers

Which mechanism does cooperativity utilize in enzyme function?

Sequential binding of multiple substrates affecting enzyme conformation. Signup and view all the answers

How do non-competitive inhibitors affect enzyme function?

They bind away from the active site and alter enzyme shape. Signup and view all the answers

What role do cofactors play in enzyme activity?

They assist in enzyme activity by providing essential chemical groups. Signup and view all the answers

In feedback inhibition, how does the end product interact with the metabolic pathway?

It inhibits an early enzyme in the production pathway. Signup and view all the answers

Which statement accurately describes the thermodynamic aspect of ATP's role in energy transfer?

ATP hydrolysis releases approximately -7 kcal/mol, making it strongly exergonic. Signup and view all the answers

How is allostery defined in the context of enzyme regulation?

Modification of enzyme activity via binding at sites other than the active site. Signup and view all the answers

What is the function of enzymes in biochemical pathways?

They provide a specific surface and lower the activation energy. Signup and view all the answers

Which of the following best describes the concept of ΔG in biochemical reactions?

It is influenced by concentration changes of reactants and products. Signup and view all the answers

Study Notes

Energy and Enzymes

Life is work, requiring energy transformations governed by thermodynamic laws.
The first law of thermodynamics states energy cannot be created or destroyed, only transformed.
Organisms obtain energy from their environment.
The second law of thermodynamics states that every energy transformation increases the entropy of the universe.
A chemical cycle: matter can't be created or destroyed.
Spontaneous changes have a negative change in free energy (ΔG<0).
ΔG = ΔH - TΔS.
ΔG = free energy, ΔH = total energy, and ΔS = entropy.
Energy flows towards disorder.
Cells need continuous energy input to maintain organization.
Energy flow in ecosystems:
- Light energy is used in photosynthesis by plants and algae, generating organic molecules and oxygen.
- Cellular respiration in mitochondria breaks down organic molecules to generate ATP.
Free energy and spontaneous reactions:
- Reactants have higher free energy than products (ΔG).
- Exergonic reactions release free energy, enabling work.
- Free energy decreases during spontaneous change.
- Energy can be interconverted, with the opposite being endergonic.
Transfer of energy drives biology:
- Anabolic processes create order, and they have a negative ΔG.
- Catabolic processes release energy, and they have a negative ΔG (cellular respiration).
Catabolism breaks down complex molecules, releasing energy.
Anabolism uses energy to synthesize complex molecules from simpler ones.
Metabolism is the organized set of transformations in a living organism.
First law of Thermodynamics: Energy can only be interconverted.
Catabolism extracts energy from complex molecules in small steps.
Anabolism: Builds new complex molecules.
ATP is the energy currency for coupling reactions:
- Catabolism provides energy from exergonic (energy-releasing) processes.
- Anabolism uses energy for endergonic (energy-consuming) processes to perform cellular work.
- ATP is converted to ADP through hydrolysis releasing energy.
ATP drives endergonic reactions by transferring phosphate groups to other molecules, causing a chemical or structural change to happen.
Catabolism provides energy to regenerate ATP from ADP.
ATP is regenerated through catabolic reactions.
Coupling ATP to drive reactions:
- ATP → ADP (ΔG= ~-7 kcal/mol).
- ATP can drive endergonic reactions by coupling it to exergonic reactions.
- ATP changes the structure of enzymes to drive the reactions.
Specificity is required for ATP and other substrates.

Enzymes and Catalysis

Enzymes increase reaction rates by lowering activation energy.
Enzymes are not consumed during reactions.
Enzymes provide a specific surface for reactions to occur in.
- They can be linked in metabolic pathways and signalling.
Chemical energy of reactants and products is unaffected by enzymes.
Reactions must be exergonic (overall energy release) for enzymes to work.
The catalytic cycle of enzymes:
- Substrates enter the active site.
- Substrates are held in place by weak interactions.
- The active site lowers activation energy.
- Substrates are converted to products and then released.
Catalytic surface in enzyme active site:
- Non-covalent binding secures substrates.
- High specificity for substrates and reaction pathways.
- Enzyme participates in the reaction chemistry.
- Stabilize transition state and represents activation energy barriers.
Enzymes are adapted to conditions (temperature, pH, cofactors).
Temperature: Mesophiles (20–40 °C), Thermophiles (>70 °C).
pH: Normal (pH 6–8), Stomach (pH 2).
Cofactors (metal ions, vitamins, small molecule chemicals).

Enzyme Regulation

Enzyme activity is regulated by:
- Inhibition (competitive or non-competitive).
- Cooperativity
- Allosteric regulation
- Feedback inhibition
Enzymes can be regulated to control pathways.
Cooperativity: Binding of one substrate can alter binding sites of other substrates, e.g., hemoglobin.
Allostery: Binding of a molecule (activator or inhibitor) away from the active site changes enzyme activity (e.g., ATP, ADP).
Feedback inhibition: End products of a pathway inhibit the early steps of that pathway to regulate production.

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Description

Explore the fundamental principles of energy transformations and enzymes in biological systems. This quiz covers thermodynamic laws, the role of energy in ecosystems, and the significance of free energy changes in chemical reactions. Enhance your understanding of how living organisms obtain and utilize energy.