Module 2 Biological Molecules Flashcards

Question

Where does most of water properties come from

Answer 1

Water molecules stick together

Answer 2

Consists of 2 hydrogen atoms covalently bonded with 1 oxygen. The oxygen has a greater affinity for electrons than the hydrogens so it pulls electrons closer. This makes oxygen slightly negative indicated by S- and the hydrogens slightly positive indicated by S+. This creates different charged regions making water a polar molecule. Because it has 2 charged regions it is dipolar.

Answer 3

Many of the properties come from the hydrogen bond. The slightly negative charge on the oxygen atom makes it attract the slightly positive hydrogen atom of another water molecule. The numerous hydrogen bonds make it very stable and cohesive structure.

Answer 4

At an air-water surface, the cohesion between water molecules produces surface tension, which can make a solid like surface explaining how a pond skater can walk on water. Within a column of water cohesion also explains why the column does not break when water molecules are pulled up a narrow tube e.g in a straw or xylem during transpiration.

Answer 5

It has polar molecules so water is attracted to any substance that is polar. Substances that can become part of water’s hydrogen bonded structure will dissolve water are called hydrophilic. Substances that cannot and will not dissolve in water are hydrophobic. Only triglycerides(lipids and fats) and large polymers eg starch do not dissolve.

Answer 6

Water absorbs/loses a large amount of heat before its temp change=specific heat capacity. Water absorbs a large amount of heat before it turns into water vapour=latent heat of vaporisation

Answer 7

High latent heat of vaporisation, evaporation is efficient for cooling eg sweating. High specific capacity, thermally stable environment for aquatic organisms, which use less energy on temp control, so internal temp of organism changes slowly so enzyme reactions are at correct rate. Ice is less dense than water so provides habitat for organisms. Water beneath remains liquid, so organism don’t freeze. Effective solvent for reactions. Cohesion eg transpiration in xylem. Surface tension, habitat for insects like pond skater. Transparent for underwater photosynthesis. High density for floating and support. Organisms can still obtain oxygen, food etc form water.