DAT Ch3 Bio Flashcards
(25 cards)
What makes water a polar molecule?
Water has polar covalent bonds, where oxygen pulls electrons more than hydrogen, making O partially negative (δ–) and H partially positive (δ⁺).
What type of bond holds water molecules together?
Hydrogen bonds — weak attractions between a hydrogen (δ⁺) and an oxygen (δ–) from different water molecules.
What is cohesion and why is it important?
Cohesion is when water sticks to itself; it’s important for transporting water in plants.
What is adhesion and how does it help plants?
Adhesion is when water sticks to other surfaces (like cell walls), helping water move upward against gravity.
What is surface tension?
The strength of water’s surface due to hydrogen bonding — it lets small insects ‘walk on water.’
What does high specific heat mean for water?
Water resists temperature change because heat must first break hydrogen bonds.
Why does water stabilize temperature?
It has high specific heat and can absorb/release a lot of heat with little temperature change.
What is heat of vaporization?
The amount of heat needed to turn water into gas — high in water due to hydrogen bonds.
How does sweating cool the body?
Evaporative cooling — the hottest water molecules evaporate, taking heat with them.
Why does ice float?
In ice, hydrogen bonds form a stable crystal lattice, spacing molecules apart, making it less dense than liquid water.
What is a solution?
A uniform mixture of a solvent and solute (e.g., saltwater).
What is the solvent in an aqueous solution?
Water.
What is a hydration shell?
A layer of water molecules that surrounds and separates dissolved ions or polar molecules.
What does hydrophilic mean?
Water-loving — substances that dissolve well in water (polar or ionic).
What does hydrophobic mean?
Water-fearing — substances that do not dissolve in water (nonpolar, like fats/oils).
What is an acid?
A substance that increases H⁺ concentration in a solution.
What is a base?
A substance that reduces H⁺ concentration (either by accepting H⁺ or releasing OH⁻).
What is pH?
A measure of H⁺ concentration: pH = –log[H⁺]; lower pH = more acidic.
What is a neutral pH?
pH 7 — equal H⁺ and OH⁻ concentrations.
How much more acidic is pH 4 compared to pH 7?
1,000× more acidic (each pH step = 10× difference in H⁺).
What is a buffer?
A substance that stabilizes pH by accepting or releasing H⁺ ions.
What buffer helps keep blood pH stable?
Carbonic acid–bicarbonate buffer (H₂CO₃ ⇄ H⁺ + HCO₃⁻).
What is ocean acidification?
CO₂ dissolves in seawater, forms carbonic acid, which increases H⁺ and lowers pH.
Why is ocean acidification a problem for marine life?
H⁺ ions reduce carbonate (CO₃²⁻), which corals and shellfish need to build shells (CaCO₃).
