Water

Question 1

Why is water essential for most biological reactions?

Answer 1

• because they take place in solution
• water is a solvent, wich means substances dissolve in it

Question 2

Can substances be transported more easily if they’re dissolved in a solvent? Relate this to water.

Answer 2

• yes
• water is a solvent, so it can easily transport all sorts of materials around plants and animals

Question 3

What is the structure of a molecule of water?

Answer 3

• one atom of oxygen joined to two atoms of hydrogen by shared electrons

Question 4

Not all the electrons on the oxygen atom are shared. What effect does this have?

Answer 4

• gives the oxygen atom a slight negative charge

Question 5

Why does the other side of each hydrogen atom have a slight negative charge?

Answer 5

• because the shared negative hydrogen electrons are pulled towards the oxygen atom

Question 6

What is a dipolar molecule? Is water a dipolar molecule?

Answer 6

• it has a partial negative charge on one side and a partial positive charge on the other

Question 7

What is a hydrogen bond?

Answer 7

• the bond between oxygen and hydrogen
• oxygen is negatively charged and hydrogen is positively charged so they attract eachother

Question 8

What is cohesion?

Answer 8

• the attraction between molecules of the same type (e.g two water molecules)

Question 9

Why are water molecules very cohesive?

Answer 9

• they’re dipolar

Question 10

Why is water great for transporting substances?

Answer 10

• waters cohesion helps it flow

Question 11

What can dissolve in the water in blood and be transported around the body?

Answer 11

• important ions

Question 12

A lot of important substances in biological reactions are ionic what does this mean?

Answer 12

• they are made from one positively charged atom/molecule and one negatively charged atom/ molecule

Question 13

How does an ion dissolve in water?

Answer 13

• the slightly positive end of a water molecule will be attracted to the negative ion, and the slightly negative end of a water molecule will be attracted to the positive ion

Question 14

What is the partial charge of H?

Answer 14

• +

Question 15

what is the partial charge of O?

Answer 15

• -

Question 16

Why is it a benefit that water has a high heat capacity?

Answer 16

• it helps keep internal body temperature fairly constant, ensuring no big temperature fluctuations so enzymes won’t denature

Question 17

What does a high heat capacity mean?

Answer 17

• it takes a large amount of heat energy to give only a small rise in temperature of the water

Question 18

give 3 examples of organisms making use of the high heat of vaporisation found in water.

Answer 18

• mammals swear and pant to cool
• reptiles open mouths so allow evaporation (cooling)
• plants cool leaves during transpiration

Question 19

What does high heat of vaporisation mean?

Answer 19

• water needs a large amount of heat to evaporate it
• as it draws hear from the surroundings, if causes a cooling effect

Question 20

Water is not easily compressed. What can it provide because of this?

Answer 20

• Turfidity in plant cells, supporting the leaves of plants
• strength in terms of the hydrostatic skeleton of animals
• support for the developing foetus (amniotic fluid)