exam 1 Flashcards
Define “chemistry”
study of matter and how it changes
Define what makes a thing “living”
- Replication
- Complex
- Organized
- Carries out energy transformations
List properties of biomolecules that make them ideal for supporting life
- most of them are organic compounds
- specific shapes and dimensions
3.functional groups determines their chemical properties
4 asymmetric
Distinguish between prokaryotic and eukaryotic cells
Prokaryotic( archaea and bacteria)
cells lack a true nucleus, have a simpler structure, and often have a single circular DNA molecule, while eukaryotic cells have a distinct nucleus, are more complex with membrane-bound organelles, linear chromosomes, and a larger size (plant, animals, fungi, protists)
Qualitatively describe enthalpy and entropy
enthalpy relates to the total energy content of a system and the heat exchanged during processes, while entropy relates to the degree of disorder or randomness within a system.
Use the relationship between enthalpy, entropy, and Gibbs free energy to determine whether or not a particular
chemical reaction is favorable
These relationships help us determine whether a particular process is spontaneous (favorable) or non-spontaneous (unfavorable)
The Gibbs free energy equation is as follows:
∆G = ∆H - T∆S
Where:
∆G is the change in Gibbs free energy.
∆H is the change in enthalpy.
∆S is the change in entropy.
T is the absolute temperature in Kelvin.
Spontaneous at given temp if:
If ∆G < 0 (negative), the process is spontaneous in the forward direction.
If ∆G > 0 (positive), the process is non-spontaneous in the forward direction
If ∆G = 0, the system is at equilibrium
Relate standard state Gibbs free energy and equilibrium constant of a chemical reaction
∆G° = -RT ln(K)
Where:
∆G° is the standard state Gibbs free energy change for the reaction.
R is the gas constant (8.314 J/(mol·K) or 0.008314 kJ/(mol·K)).
T is the absolute temperature in Kelvin.
ln represents the natural logarithm.
K is the equilibrium constant for the reaction.
Calculate Gibbs free energy for a system not at equilibrium
∆G = ∆G° + RT ln(Q)
Where:
∆G is the Gibbs free energy change for the non-equilibrium state.
∆G° is the standard state Gibbs free energy change.
R is the gas constant (8.314 J/(mol·K) or 0.008314 kJ/(mol·K)).
T is the absolute temperature in Kelvin.
ln represents the natural logarithm.
Q is the reaction quotient, which is a measure of the ratio of the concentrations (or activities) of products to reactants in the non-equilibrium state.
Describe how the structure and chemical properties of water give rise to solvation, dialysis, and clathrate and
micelle formation
Solvation: Water’s ability to form hydrogen bonds with polar or charged substances allows it to disperse and surround solute particles, leading to the dissolution of solutes in aqueous solutions.
Dialysis: Water’s small size and ability to form hydrogen bonds enable it to pass through semipermeable membranes during dialysis, separating solute molecules from a solvent.
Clathrate Formation: Water molecules can trap small molecules or gases within their lattice-like structure, forming clathrate hydrates. This is significant in natural environments like deep-sea sediments where methane hydrates are found.
Micelle Formation: Amphiphilic molecules self-assemble in aqueous solutions, with hydrophobic regions clustering in the core and hydrophilic regions facing the surrounding water molecules. This property is crucial in processes like emulsification and the absorption of dietary fats.
Illustrate how nonpolar molecules spontaneously separate from water and how this represents the state of
greatest entropy
The spontaneous separation of nonpolar molecules from water is driven by the principle of increasing entropy. When nonpolar molecules are introduced into a polar solvent like water, they disrupt the structured arrangement of water molecules due to their lack of polar groups. To maximize disorder and entropy, nonpolar molecules tend to spontaneously aggregate or separate from water. This separation, known as the hydrophobic effect, reduces unfavorable interactions, releases water molecules from their ordered state, and leads to a system with greater entropy. In this separated state, both water and nonpolar molecules adopt a more disordered arrangement, representing a state of maximum entropy.
Define amphiphilic molecules and describe their behavior in water
Micelle Formation: Amphiphilic molecules spontaneously organize into micelles, with hydrophilic heads facing outward in contact with water and hydrophobic tails clustering in the core to minimize contact with water. This structure stabilizes the system.
Emulsification: Amphiphilic molecules are used to create stable emulsions by surrounding and dispersing hydrophobic substances (like oils) in water. The hydrophilic heads interact with water, while the hydrophobic tails interact with the hydrophobic substances, preventing them from coalescing.
Biological Significance: In biological systems, amphiphilic molecules like phospholipids form the basis of cell membranes, with hydrophilic head groups interacting with the aqueous environment and hydrophobic tails creating the lipid bilayer.
Detergent Action: Many detergents and surfactants are amphiphilic molecules that can solubilize hydrophobic substances, allowing them to be removed in water due to their interaction with the hydrophilic heads of the detergent molecules.
Describe and rank the relative strengths of non-covalent (electrostatic, hydrogen bond, van der Waals)
interactions in water
Ranking the relative strengths of these interactions in water:
Electrostatic Interactions (Strongest)
Hydrogen Bonds
Van der Waals Interactions (Weakest)
Electrostatic Interactions: These are the strongest non-covalent interactions. They arise from the attraction between oppositely charged ions or molecules. In water, they play a vital role in dissolving salts and stabilizing charged biomolecules.
Hydrogen Bonds: Hydrogen bonds are weaker than electrostatic interactions but stronger than van der Waals forces. They form between hydrogen atoms covalently bonded to electronegative atoms (e.g., oxygen) and neighboring electronegative atoms. In water, hydrogen bonds contribute to its unique properties and are essential for biological molecule stability.
Van der Waals Interactions: These are the weakest of the three non-covalent interactions. They result from temporary fluctuations in electron distribution, inducing temporary dipoles in molecules. In water, van der Waals interactions are involved in the attraction between nonpolar molecules and are significant in hydrophobic interactions.
Relate hydrogen ion concentration to a pH scale
pH = -log[H⁺]
A pH value less than 7 indicates acidity, with lower values indicating stronger acidity (higher [H⁺] concentration).
A pH value greater than 7 indicates alkalinity, with higher values indicating stronger alkalinity (lower [H⁺] concentration).
Use the Henderson-Hasselbalch equation to determine the pH of buffered solutions
pH = pKa + log([A⁻]/[HA])
Where:
pH is the pH of the buffered solution.
pKa is the negative logarithm (base 10) of the acid dissociation constant (Ka) of the weak acid (or base) in the buffer.
[A⁻] is the concentration of the conjugate base.
[HA] is the concentration of the weak acid.
Describe how weak acid/conjugate base pairs function as buffers
eak acid/conjugate base pairs function as buffers by maintaining a stable pH in a solution. They achieve this by shifting their equilibrium to absorb or release H⁺ ions in response to changes in acidity or alkalinity, thereby resisting large pH changes.
