A1.1 WaterIB Biology SL: Flashcards
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Why is water described as the medium for life?
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- Why is water described as the medium for life?
- The first cells originated in water, and most processes of life, including most enzyme-catalysed reactions, still occur in water.
- Why is a water molecule polar?
- Oxygen attracts the shared electrons more strongly than hydrogen, so O is partially negative (δ−) and each H partially positive (δ+).
- What is a hydrogen bond between water molecules?
- An attraction between the δ+ hydrogen of one water molecule and the δ− oxygen of another.
- Define cohesion.
- Attraction between water molecules due to hydrogen bonding.
- How does cohesion allow water transport in xylem?
- Evaporation from leaves creates tension; cohesion keeps the water column continuous so the pull is transmitted from the roots.
- What is surface tension and why does it matter to some animals?
- Resistance of the water surface to breaking, due to cohesion; small animals such as pond skaters can live on the surface.
- Define adhesion.
- Attraction of water to other polar or charged materials, e.g. cellulose or soil particles.
- Give two examples of capillary action in plants.
- Water moving through soil towards roots, and water moving through cellulose cell walls in leaves.
- Why do glucose and sodium ions dissolve in water?
- They are polar or charged, so they are attracted to (and hydrogen-bond with) polar water molecules.
- Give two molecules whose function depends on being hydrophobic.
- Phospholipids (membrane barrier) and triglycerides (energy storage without osmotic effect); also waxes.
- How do buoyancy and viscosity differ between water and air?
- Water is far denser (more buoyancy) and far more viscous (more drag) than air.
- Why does a ringed seal need thick blubber?
- Water conducts heat much faster than air, so heat is lost quickly in cold water; blubber insulates.
- What does water's high specific heat capacity mean for aquatic habitats?
- Water temperature changes slowly, giving stable habitats.