2.4 Water + Inorganic ions

Question 1

Why is water a polar molecule?

Answer 1

• O is more electronegative than H —> so
  attracts the electrons in the
  covalent bond more strongly.
• Forms O 𝛿- (slight negative charge) &
  H 𝛿+ (slight positive charge).

Question 2

State 5 biologically important properties
of water

Answer 2

• An important solvent in reactions
  ● Metabolite
  ● High specific heat capacity; buffers temperature
  ● High latent heat of vapourisation; provides a cooling effect with loss of water through evaporation
  ● Strong cohesion between water molecules; supports water columns and provides surface tension

Question 3

Explain the role of phosphate ions in the body. (4)

Answer 3

component of:
● DNA
● ATP
● NADP
● cAMP

Question 4

How much of your body is made up of water

Answer 4

60-70%

Question 5

Why does water have a high specific heat capacity

Answer 5

• Water molecules tend to stick together so more energy is required to separate them
• Without Hydrogen bonds it would be a gas at room temperature- Alot of energy is required to evaporate 1 gram of water

Question 6

What is the effect of the high specific latent heat of water

Answer 6

Water acts as a buffer to any sudden temperature changes

Question 7

Why is sweat an effective means of reducing body temperature

Answer 7

Because body heat is used to evaporate the water that heat energy needs to break the H bonds in water

Question 8

How is water important in metabolism

Answer 8

Because water is used to break down many complex molecules by hydrolysis and water is also produced in reactions (condensation)

Question 9

What is the structure of Water

Answer 9

• Dipolar molecule
• Unevenly distributed charges -oxygen is slightly negative hydrigen is slightly positive-

Question 10

How is water a metabolite

What are the reactions water is used in

Answer 10

Water is involved in many reactions such as:
* Photosynthesis
* Hydrolysis
* Condensation reactions
Due to this plasma is made up of approximaiately 90% water

Question 11

What is a solvent

Answer 11

A solvent is something that many substances dissolve in

Question 12

Why is water a good solvent? (3)

Answer 12

• It is a dipolar molecule and polar molecules dissolve readily in water
• The slight positive charge on hydrogen atoms will attract any negative ions solutes and the slight negative charge on oxygen atoms of water will attract any positive ions in solutes
• Many essential substances are polar which allow them to dissolve in water —> enables them to be transported easily around animals and plants, either in blood or xylem to cells they are needed in inside of the organism

Question 13

Explain how water has a High specific heat capacity and why is this important

Answer 13

• A lot of energy is required to raise the temperature of water —-> H bonds need to be broken and there are plenty of h bonds in water which require lots of energy to break them—-> this is useful to organisms as it means temperature of water remains relatively stable even if the temperature fluctuates significantly

Question 14

What is a benefit of large proportions of organisms being made up of mainly water

Answer 14

• The internal temp of plants and animals remain relatively constant despite the outside temperature.
• This is important so enzymes do not denature or reduce in activity with temperature fluctuations as it provides a stable environment

Question 15

How does water have a high latent heat of vapourisation?

Answer 15

• A lot of energy is required to convert water in its liquid state to a gaseous state due to hydrogen bonds needing to be broken and provide water with a significant cooling effect.

Question 16

Give an example of why having a high specific latent heat of vaporisation is important (Water wise)

Answer 16

When humans sweat they release water on to their skin —> large amounts of heat energy from the skin is transferred to the water to evaporate it and therefore removing a lot of heat and cooling the organim

Question 17

What does Cohesion mean

Answer 17

Term used to describe water mooecules sticking together by hydrogen bonds

Question 18

Why is Cohesion important to living organims

Answer 18

• Due to water molecules sticking together when water moves up the xylem in plants due to transpiration, it is as a continuous column of water.
• This is advantageous as it is easier to draw up a column rather than individual molecules
• Cohesion also provides surface tension to water this enables small invertebrates to move and live on the surface providing them a habitat away from predators within water

Question 19

What are inorganic ions and where are
they found in the body?

Answer 19

● Ions that do not contain carbon atoms.
● Found in cytoplasm & extracellular
fluid.
● May be in high or very low
concentrations.

Question 20

Explain the role of hydrogen ions in the
body.

Answer 20

● High concentration of H+ = low (acidic)
pH.
● H+ ions interact with H-bonds & ionic
bonds in tertiary structure of proteins,
which can cause them to denature