What is energy?
The ability to do work.
What is kinetic energy?
The energy of motion — energy actively being used.
What is potential energy?
Stored energy in an object that has the capacity to move but is not currently in motion.
How does potential energy relate to kinetic energy in living organisms?
All work carried out by organisms involves the transformation of potential energy into kinetic energy.
How does energy enter the living world?
Energy from the sun is captured by photosynthesis and stored in carbohydrates as potential energy.
What is thermodynamics?
The study of energy changes — all forms of energy can be converted to heat, making heat a convenient measure.
What is the first law of thermodynamics?
Energy cannot be created or destroyed — it can only change from one form to another. The total amount of energy in the universe remains constant.
What is the second law of thermodynamics?
Disorder in a closed system tends to continuously increase — entropy always increases.
What is entropy?
A measure of the degree of disorder in a system.
How do cells maintain order despite the second law of thermodynamics?
By using energy to locally increase organization, keeping themselves more ordered than their surroundings.
What are reactants?
The original molecules present before a chemical reaction occurs — also called substrates.
What are products?
The molecules that result after a chemical reaction has taken place.
What is an endergonic reaction?
A chemical reaction in which the products contain more potential energy than the reactants — requires an input of energy and does not occur spontaneously.
What is an exergonic reaction?
A chemical reaction in which the products contain less potential energy than the reactants — releases energy and tends to occur spontaneously.
What is activation energy?
The energy required to destabilize existing chemical bonds and initiate a chemical reaction — a “nudge” needed to get a reaction started.
Why don’t all exergonic reactions occur spontaneously right away?
Because they still require an initial input of activation energy to break existing bonds before the reaction can proceed.
What is catalysis?
The process of lowering the activation energy of a reaction, causing it to proceed faster.
What are enzymes?
Protein catalysts produced by cells that lower the activation energy of specific chemical reactions.
What is the active site of an enzyme?
The specific region on the enzyme surface where the substrate binds and the reaction is catalyzed.
What is a substrate?
The specific reactant molecule that binds to an enzyme’s active site.
What is induced fit?
The way an enzyme slightly changes shape to embrace its substrate more intimately after binding — like a hand wrapping around a baseball.
Is an enzyme consumed in a reaction?
No — the enzyme is not affected by the reaction and can be reused repeatedly.
What is a biochemical pathway?
A fixed sequence of chemical reactions in which the product of one reaction becomes the substrate for the next.
Why are enzymes of a biochemical pathway often positioned near each other in the cell?
Close proximity allows reactions to proceed faster by quickly passing products from one enzyme to the next.
