Chapter 1 Flashcards
What are the key differences between eukaryotic and prokaryotic cells?
Eukaryotes: Have membrane-bound organelles, a nucleus, and linear DNA.
Prokaryotes: No nucleus, circular DNA, smaller, unicellular.
Both: Carry out biochemical processes and have similar metabolic pathways.
What are the four nitrogenous bases of DNA, and how do they pair?
Adenine (A) pairs with Thymine (T) (2 hydrogen bonds).
Guanine (G) pairs with Cytosine (C) (3 hydrogen bonds).
DNA strands are antiparallel and form a double helix.
Rank the following bonds in order of strength: covalent, ionic, hydrogen, van der Waals.
Covalent > Ionic > Hydrogen > van der Waals
Covalent: Strongest, formed by electron sharing.
Ionic: Noncovalent, occurs between fully charged atoms.
Hydrogen: Weak dipole-dipole interactions.
van der Waals: Weakest, due to transient asymmetry in electron distribution.
Why is water a polar molecule, and what is the hydrophobic effect?
Water is polar due to unequal sharing of electrons between oxygen and hydrogen.
The hydrophobic effect drives nonpolar molecules together in water, increasing entropy and stabilizing protein folding & membrane formation.
State the First and Second Laws of Thermodynamics and their importance in biochemistry.
First Law: Energy cannot be created or destroyed.
Second Law: The total entropy of a system and its surroundings always increases.
Biochemical reactions must follow these laws, ensuring energy flow and disorder increase.
What is the Gibbs free energy equation, and how does it determine if a reaction is spontaneous?
ΔG=ΔH−TΔS
ΔG < 0 → Spontaneous (exergonic).
ΔG > 0 → Non-spontaneous (endergonic).
Determines whether biochemical reactions will proceed.
What is the ion product of water, and how do pH and pOH relate?
Kw=[H+][OH−]=10^−14
𝑝𝐻+𝑝𝑂𝐻=14
If pH decreases, [H⁺] increases (acidic).
If pH increases, [OH⁻] increases (basic).
How does pH affect the DNA double helix?
High pH → Guanine loses a proton, disrupting base pairing, leading to denaturation.
Low pH → Protonates bases, affecting hydrogen bonding.
What does the pKa value indicate about a molecule’s protonation state?
pKa = pH at which a group is 50% deprotonated.
pH > pKa → The group is deprotonated (loses H⁺).
pH < pKa → The group is protonated (gains H⁺).
How do buffers regulate pH in biological systems?
Buffers resist pH changes by accepting or donating H⁺.
Work best when pH is close to the buffer’s pKa.
Example: Phosphate buffer system in cells.
What is the Henderson-Hasselbalch equation, and how does it describe buffer systems?
pH=pKa+log [A−]/[HA]
If [A⁻] increases → pH increases (becomes more basic).
If [HA] increases → pH decreases (becomes more acidic).
