Definitions
Name the three forms of energy for this course, and give a cellular example of one.
Electrical, thermal, and potential. Example: ions crossing a membrane, molecular motion, or electron position in a bond.
What is the small region of an enzyme where the reaction actually happens called?
The active site.
Define free energy.
The total energy available to do work.
What are the components of a chemical reaction?
Reactants and products.
What is the most basic source of energy for any organism?
Sunlight
In biology, potential energy is mostly about the position of what?
Electrons in chemical bonds.
What chemical agent does an enzyme act like?
A catalyst.
Define entropy.
A measure of molecular disorder or randomness.
Define exergonic.
A chemical reaction that releases energy.
What molecule do most cells get their energy from?
ATP
Define and name the two metabolic pathways.
Anabolic uses energy to construct macromolecules. Catabolic breaks down of organic matter to harvest energy.
How does an enzyme affect activation energy? How does it affect the free energy of the reactants and products?
It lowers activation energy. It does not change the free energy of the reactants or the products at all.
What three things combine to make up free energy?
Entropy, thermal energy, and potential energy.
Define endergonic.
A reaction that stores energy. Free energy rises and products sit higher.
Define phosphorylation.
Adding a phosphate group to a molecule, usually taken from ATP. The added charges repel nearby negative charges, so the molecule ends up with higher free energy than before.
Define activation energy.
The energy needed to get a reaction through its transition state.
Name the two ways an active site speeds up a reaction.
It holds the reactants in the correct orientation, and it stabilizes the transition state, which lowers activation energy.
A reaction is spontaneous when free energy is higher or lower in the products than in the reactants?
Lower
Why does ATP carry so much potential energy?
Four negative charges are crowded together on the phosphate groups. Like charges repel, pushing electrons away from the nuclei.
Why do biologists say that life is nonspontaneous?
Building large ordered molecules from small ones lowers entropy and costs energy, so every cell has to pay for its own order continuously.
What is the transition state, and why does free energy peak there?
The point where old bonds are partly broken and new bonds have not formed yet. It is the least stable arrangement, so free energy spikes.
An enzyme works best at pH 2. Where in the body would you expect to find it, and how do you know?
The stomach. An enzyme's optimum matches the environment it evolved to work in.
Name two differences between spontaneous and non spontaneous processes.
Spontaneous reactions need no energy input and happen on their own, free energy drops, and entropy generally increases. Nonspontaneous reactions require an energy input, free energy rises, and entropy generally decreases.
Electrons in which bond have higher potential energy, C-H or C=O? Why?
C-H. In C=O, oxygen is far more electronegative, so it holds the electrons tightly and close in, which lowers their potential energy.
How does ATP make a nonspontaneous reaction happen?
Energetic coupling. A phosphate from ATP is added to one of the reactants, which raises that reactant's free energy so the products now sit lower.