2.4 Water + Inorganic ions

Question 1

Why is water a polar molecule?

Answer 1

O is more electronegative than H, so
attracts the electron density in the
covalent bond more strongly.
forms O 𝛿- (slight negative charge) &
H 𝛿+ (slight positive charge).

Question 2

State 4 biologically important properties
of water

Answer 2

due to polarity & intermolecular H-bonds:
● Metabolite / solvent for chemical reactions in
the body.
● high specific heat capacity.
● high latent heat of vapourisation.
● cohesion between molecules

Question 3

Explain why water is significant to living
organisms

Answer 3

Solvent for polar molecules during metabolic
reactions.
● Enables organisms to avoid fluctuations in
core temperature.
● Cohesion-tension of water molecules in
transpiration stream.

Question 4

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

Answer 4

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

Question 5

Explain the role of hydrogen ions in the
body.

Answer 5

● 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

Question 6

Explain the role of iron ions in the body.

Answer 6

Fe2+ bonds to porphyrin ring to form haem
group in haemoglobin.
Haem group has binding site to transport 1
molecule of O2 around body in bloodstream.
4 haem groups per haemoglobin molecule.

Question 7

Explain the role of sodium ions in the
body

Answer 7

Involved in co-transport for absorption of
glucose & amino acids in lumen of gut

Involved in propagation of action
potentials in neurons .

Question 8

Explain the role of phosphate ions in the
body.

Answer 8

component of:
● DNA
● ATP
● NADP
● cAMP

Question 9

Why does water have a high specific heat capacity

Answer 9

The 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 10

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

Answer 10

Water acts as a buffer to any sudden temperature changes and variations

Question 11

Why is sweat an effective means of reducing body temperature

Answer 11

Because body heat is used to evaporate the water

Question 12

How is water important in metabolism

Answer 12

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