BIOLOGICAL MOLECULES - water and inorganic ions

Question 1

why is water a polar molecule?

Answer 1

O is more electronegative than H so attracts the electron density more strongly in the covalent bond
O is partially negative
H is partially positive

Question 2

state 4 biologically important properties of water

Answer 2

due to polarity and intermolecular H-bonds
-metabolite
-solvent
- high specific heat capacity
-high latent heat of vaporisation
-cohesion and adhesion between molecules

Question 3

explain water’s role as a metabolite?

Answer 3

• involved in many reactions such as respiration photosynthesis, hydrolysis, condensation reactions
• cytoplasm is mainly composed of water
• water is used in hydrolysis - used to break bonds

Question 4

explains water’s role as a solvent?

Answer 4

• many substances dissolve in it
  -polar or charged molecules dissolve readily in water.
  -the partially positive charge on the hydrogen will attract negative ions and a partially negative charge on oxygen to attract positive ions.
• non polar molecules cannot dissolve as they are hydrophobic
  -dissolving H2O enables water to be transported easily.

Question 5

state and explain why SHC of water is important?

Answer 5

-a lot of energy is required to raise the temperature of water.
-this is useful to organisms as the temperature of water remain stable.
-importance for enzymes to not denature or reduce activity with temperature fluctuations.
- provides a stable environment in terms of temperature for aquatic organisms.

Question 6

State and explain why large latent heat of vaporisation of water is important?

Answer 6

.-a lot of energy is required to convert liquid water to a gas.
-this is good for organisms as water provides a cooling effect= heat energy is transferred to water to evaporate. it is removing a lot of heat and cooling the organism when humans sweat.

Question 7

Explain strong cohesion of water?

Answer 7

-water molecules stick together
-water can move up the xylem in plants due to transpiration as it is a continuous column of water.

Question 8

Explain surface tension of water?

Answer 8

-cohesion provide surface tension= allows more invertebrates to move and live on surface, providing them a habitat away from predators within water.

Question 9

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

Answer 9

• ions that do not contain carbon atoms
• found in cytoplasm and extracellular fluids
• may be in high or very low concentrations

Question 10

Explain the role of hydrogen ions in the body?

Answer 10

high conc of H+ = acidic pH
H+ ions interact with H-bonds and ioinic bonds in tertiary structure of proteins which can cause them to denature.

Question 11

explain the role of iron ions in the body?

Answer 11

Iron (II) bonds to porphyrin ring to form haem group in haemoglobin
Haem group has binding site to transport 1 molecule of O2 around body in blood stream
4 Haem groups per haemoglobin molecule

Question 12

explain the role of sodium ions in the body?

Answer 12

Involved in co-trasnport for absorption of glucose and amino acids in lumen of gut.
involved in propagation of action potential in neurons

Question 13

Explain the role of phosphate ions in the body?

Answer 13

component of:
ATP
DNA
NADP
cAMP