2.4 Water and its functions

Question 1

Describe the dipolar structure of water.

Answer 1

• water is made up of 2 hydrogen atoms and one oxygen atom.

- the oxygen has a slightly negative charge, whilst hydrogen has a slightly positive one.

Question 2

describe how water is used in hydrogen bonding.

Answer 2

• the opposite poles of water molecule are attracted to each other
• the attractive force is known as a hydrogen bond
• the force is weak but the force of water molecules to stick together gives it unusual properties.

Question 3

Describe the specific heat capacity of water.

Answer 3

• because oxygen molecules are connected by hydrogen bonds it takes more energy to break them.
• without H bonds it would be a gas at room temperature
• it acts as a buffer against sudden temperature change, making aquatic environments stable.

Question 4

Describe the latent heat of vaporization of water.

Answer 4

• hydrogen bonds mean it is quite high

- Evaporation is an effective way of cooling as body heat is used to evaporate sweat

Question 5

Describe the cohesion and surface tension of water.

Answer 5

• water has large cohesive forces which allow it to be pulled up through a tube (EG: the xylem)
• when water meats air it is pulled back into the body of water (surface tension)

Question 6

How is water used in metabolism?

Answer 6

• it is used to break down complex molecules by hydrolysis and is produced in condensation reaction
• chemical reactions take place in aqueous medium
• Water is a raw material in photosynthesis

Question 7

what does water dissolve as a solvent?

Answer 7

• gases (O2 and CO2)
• waster (urea and ammonia)
• inorganic ions and small hydrophylic molecules (amino acids, monosaccharides and ATP)
• Enzymes whose reactions take place in solution

Question 8

What are 3 important features of water?

Answer 8

• evaporation cools organisms and regulates temperature
• not easily compressed, so provides support
• it is transparent so aquatic plants can photosynthesize

Question 9

Where are inorganic ions found?

Answer 9

• in solution in the cytoplasm of cells and in body fluids and parts of larger molecules
• their function relates to their properties