Biological Molecules p66-67

Question 1

Name the two reasons why that water is important.

Answer 1

• major component of cell; 70-95% of cells
  (we are 60% water)
• provides environment for organisms which live in water (3/4 of Earth is covered in water)

Question 2

Without water…

Answer 2

…life would not exist

Question 3

How can water exist as a liquid at normal Earth temperatures?

Answer 3

Water molecules are held together by hydrogen bonds. Small molecules such as water molecules usually exist as a gas at normal Earth temperatures.

Question 4

Why is it difficult to separate water molecules?

Answer 4

They are held together by hydrogen bonds, so a lot of energy is needed to overcome the bonds.
– easier to separate similar compounds with no hydrogen bonds

Question 5

Water provides a medium for..

Answer 5

…molecules and ions to mix in; a medium in which life can evolve.

Question 6

Water is a solvent. What is it ideal for?

Answer 6

ideal as a transport medium

Question 7

What happens to non-polar molecules in water?

Answer 7

Non-polar molecules such as lipids are pushed together, because water molecules are attracted to each other.

Question 8

A chemical dissolves in water..

Answer 8

its ions and molecules are free to move and react with other chemicals. Most processes in living organisms take place this way.

Question 9

What two things are water molecules attracted to, allowing them to dissolve?

Answer 9

Water molecules are attracted to ions and polar molecules. The water molecules collect around them and separate them.

Question 10

Define specific heat capacity.

Answer 10

The amount of heat energy required to raise the temperature of 1kg of a substance by 1 degree celsius.

Question 11

Describe the specific heat capacity and latent heat of vaporisation of water.

Answer 11

high, hydrogen bonds must be broken

Question 12

What makes it difficult for water to move freely?

Answer 12

Hydrogen bonds make the water molecules stick together.

Question 13

What happens to molecules when the temperature is raised?

Answer 13

Molecules gain energy and move more rapidly.

Question 14

The high specific heat capacity of water makes it..

Answer 14

..more temperature resistant.

Question 15

Name two situations in which the high specific heat capacity of water is beneficial.

Answer 15

• Water temperature in bodies and cells is relatively constant compared to the air surrounding them. So, biochemical reactions remain relatively constant.
• Stable habitats for aquatic organisms.

Question 16

How can an organism prevent dehydration when losing large amounts of heat energy?

Answer 16

there is very little water loss for a large amount of heat energy loss

Question 17

Where do water molecules get their energy to break the hydrogen bonds?

Answer 17

energy is lost from the environment and transferred to the water molecules

Question 18

Give examples of cooling mechanisms in mammals.

Answer 18

sweating and panting

Question 19

Give an example of a cooling mechanism in plants.

Answer 19

Transpiration, which cools down leaves.

Question 20

How much energy is required to freeze water and how is this beneficial?

Answer 20

A large amount of energy. Aquatic animals don’t freeze in their environments easily. High water content animals don’t freeze easily.