Biology Midterm #2 Fall 2026

What is energy? What are the two types?

Energy - The capacity to do work or cause change

1) Potential
2) Kinetic

What is the “ultimate” source of energy for the planet? And what is the most convenient way to measure energy?

The sun is the ultimate energy source. Heat is the best way to measure energy.

What is a calorie?

A unit of measurement for energy, which is the amount of heat it takes to raise the temperature of 1 gram of water by 1 degree celsius.

Compare oxidation vs. reduction

Oxidation - loss of electrons
Reduction - gain of electrons

What is the first law of thermodynamics?

Energy cannot be created or destroyed, only transformed. During conversions, some energy is lost as heat.

What is the second law of thermodynamics?

Entropy (disorder) is continuously increasing → An increase in entropy favours spontaneity, but it doesn't guarantee that a process is spontaneous.

Define Gib’s Free Energy, Enthalpy, and Entropy.

GFE (G) - Energy available to do work = DeltaH - T(DeltaS)

Enthalpy - Energy in a molecules bonds

Entropy - Disorder (or unavailable energy)

Compare positive vs. negative deltaG

(+) - products have more free energy than reactants - Enthalpy is increased and/or Entropy is decreased - Endergonic

(-) - Products have less free energy than reactants - Enthalpy is decreased and/or Entropy is increased - Exergonic

What is activation energy? What is a consequence of a larger required amount of AE?

Extra energy required to destabilize existing bonds and initiate a chemical reaction

Higher activation energy = slower reaction

What are two ways to increase reaction rate?

1) Increase temperature of molecules

2) Lower activation energy

What are catalysts? What are the two things they can’t do?

Substances that influence chemical bonds in a way that lowers activation energy

1) Can’t make endergonic (non-spontaneous) reactions exergonic (spontaneous)

2) Can’t alter the proportion of reactant turned into product

What are ATP/ADP/AMP and what are they made of?

ATP - Primary energy currency of the cell - Made of ribose (5C sugar), adenine, and 3 Phosphates.
ADP - Adenosine diphosphate
AMP - Adenosine monophosphate

Describe the ATP cycle

1) ATP Hydrolysis - ATP loses its terminal phosphate and becomes ADP + P, releasing free energy (spontaneous)

2) ATP Synthesis - Energy is used to add phosphate to ADP, reforming ATP (non-spontaneous)

What is ATP not a suitable long-term energy storage? What are some better options for long term energy storage?

1) Phosphate bonds too unstable and cells only store a few seconds worth of ATP

2) Carbohydrates and fats are much better long-term energy storages

What are enzymes?

Biological catalysts - most are proteins (some are RNA) - Not changed or consumed in a reaction

Explain the 5 steps in Enzyme-Substrate interactions. What is the short form equation of this process?

1) Substrate approaches the enzyme's active site.

2) Binding occurs between the substrate and active site (induced fit - substrate slightly alters shape of enzyme active site)

3) Enzyme-substrate complex forms.

4) Reaction occurs: Enzyme lowers activation energy, converting substrate into products.

5) Products are released, leaving the enzyme ready to be reused.

Short form: E + S → [ES] → E + P