Enzymes, Energy, and Metabolism

Flashcards covering key principles of cellular energetics, thermodynamics, metabolic pathways, enzyme mechanics, cofactors, and ATP dynamics.

How is energy defined in the context of cellular processes?

Energy is defined as the ability to do work or bring about change.

What are five essential biological activities that require energy in cells?

Energy is required to transport materials against gradients, build biomolecules (anabolism), degrade molecules (catabolism), enable movement, and carry out reproduction.

What is metabolism?

Metabolism is the sum of cellular chemical reactions in a cell.

How do exergonic and endergonic reactions differ regarding free energy and spontaneity?

Exergonic reactions release energy and occur spontaneously because products have less free energy than reactants. Endergonic reactions require energy input and are nonspontaneous because products have more free energy than reactants.

What is the Law of Conservation of Energy?

The Law of Conservation of Energy states that energy cannot be created or destroyed, but it can be changed from one form to another (for example, photosynthesis converting solar energy into chemical energy).

What is the Law of Entropy?

The Law of Entropy states that when energy is changed, there is a loss of energy available to do work. No energy conversion process is 100% efficient, and the majority of energy is lost as dissipated heat.

Based on the provided illustration, how are potential energy, kinetic energy, and mechanical energy defined and related?

Potential energy is stored energy (hammer held above nail), kinetic energy is energy of motion (hammer swinging down), and mechanical energy is the combination of kinetic energy plus potential energy.

What are enzyme cofactors and coenzymes?

Cofactors are molecules required to activate enzymes (such as $FAD$ and $NAD^+$ in cellular respiration, and $NADP^+$ in photosynthesis). Coenzymes are nonprotein organic molecules, and vitamins are required for their synthesis.

How do substrate concentration, optimal pH, and temperature affect enzymatic rate?

Enzyme activity increases with substrate concentration, and most enzymes are optimized for a particular pH. Enzyme activity increases with temperature because warmer temperatures cause more collisions between enzyme and substrate, but hot temperatures can denature and destroy enzymes.

Based on the provided graph, how does body temperature affect reaction rates in ectothermic versus endothermic animals?

Body temperature in ectothermic animals often limits rates of reactions, whereas body temperature in endothermic animals promotes rates of reactions, following an optimal curve across varying temperatures.

What is Energy of Activation ($E_A$) and how do enzymes affect it?

Energy of Activation ($E_A$) is the energy that must be added to initiate a reaction; it prevents molecules from spontaneously degrading within cells. Enzymes operate by lowering the energy of activation by bringing substrates into contact with one another.

What is the Induced Fit Model of enzyme-substrate binding?

In the Induced Fit Model, the active site of an enzyme complexes with substrates, inducing the enzyme to undergo a slight alteration to achieve optimum fit.

How do enzymatic degradation and synthesis reactions differ?

In degradation, an enzyme complexes with a single substrate and breaks it apart to form two product molecules. In synthesis, an enzyme complexes with two substrate molecules, joining them to release a single product.

What role do enzymes play as catalysts in a metabolic pathway?

Enzymes are protein molecules that function as catalysts to accelerate reactions. Each reaction in a metabolic pathway requires a unique and specific enzyme, and end products will not form without all specific enzymes present and functional.

In the sequence $A \rightarrow B \rightarrow C \rightarrow D \rightarrow E \rightarrow F \rightarrow G$, what roles do the letters play in the metabolic pathway?

$A$ is the initial reactant or substrate, $B, C, D, E, \text{ and } F$ are intermediates, and $G$ is the end product.

What is Adenosine triphosphate (ATP) composed of, and how is it maintained in cells?

ATP is a high-energy compound composed of adenine, ribose (together forming adenosine), and three phosphate groups. It is not stored, but is constantly generated from Adenosine diphosphate (ADP) through the ATP cycle.

How is energy coupled between exergonic and endergonic reactions via ATP?

Energy released by exergonic reactions is captured in ATP, which is then used to drive endergonic reactions.