Chapter 3 Flashcards
What is an exergonic reaction?
A reaction where ΔG is negative because products contain less free energy than reactants
Exergonic reactions are spontaneous processes.
What characterizes an endergonic reaction?
A reaction where ΔG is positive because products contain more free energy than reactants
Endergonic reactions are nonspontaneous processes.
What is activation energy?
The initial input of energy required to start a reaction
Both exergonic and endergonic reactions require activation energy.
What drives diffusion across a membrane?
An increase in entropy
Molecules move spontaneously from higher concentration to lower concentration.
Define equilibrium in chemical reactions.
A state of maximum stability where reactants and products are converted at equal rates
At equilibrium, there is no capacity to do work.
What happens to free energy as a system moves toward equilibrium?
The free energy change (ΔG) of the system becomes lower
At equilibrium, ΔG = 0.
Are living systems counter to the laws of thermodynamics?
No, they maintain low entropy by importing energy and matter
Living systems uphold the second law of thermodynamics by releasing energy and disordered molecules.
What is a metabolic pathway?
A series of sequential reactions where products of one reaction are used as reactants for the next
Metabolic pathways can be catabolic or anabolic.
What is catabolism?
The breakdown of complex molecules into simpler compounds, releasing energy
Examples include the breakdown of sugars, amino acids, and fatty acids.
What is anabolism?
The building of complex molecules from simpler units, requiring an input of energy
Examples include the synthesis of proteins from amino acids.
What role does ATP play in metabolism?
ATP provides energy through hydrolysis of phosphate bonds
ATP hydrolysis is an exergonic reaction that releases free energy.
What is energy coupling?
The coupling of an endergonic reaction to an exergonic reaction
ATP hydrolysis can drive non-spontaneous reactions.
What is the ATP/ADP cycle?
The continuous breakdown and resynthesis of ATP
ATP synthesis is linked to catabolic reactions.
What are enzymes?
Special proteins that increase the rate of chemical reactions
Enzymes act as biological catalysts.
What is activation energy (EA)?
The initial energy investment required to start a reaction
Molecules that gain necessary activation energy occupy the transition state.
What is the function of enzyme cofactors?
Nonprotein groups necessary for catalysis to occur
Examples include metallic ions and coenzymes such as vitamins.
What is competitive inhibition?
When an inhibitor competes with the normal substrate for the active site
Competitive inhibitors can be reversible or irreversible.
What is allosteric regulation?
The reversible binding of a regulatory molecule to an allosteric site on the enzyme
It can convert enzymes between high-affinity and low-affinity states.
How do temperature and pH affect enzyme activity?
Each enzyme has optimal temperature and pH for peak efficiency
Deviations from these optima can reduce reaction rates.
What is feedback inhibition?
When the product of an enzyme-catalyzed pathway acts as a regulator of the reaction
This mechanism helps conserve cellular resources.
