2.2 Water

Question 1

What to the hydrogen and oxygen share?

Answer 1

Each hydrogen shares a pair of electrons with the oxygen

Question 2

Why does the oxygen pull the electrons closer?

Answer 2

It has a greater affinity for the electrons than the hydrogen

Question 3

What is the the charge of the oxygen?

Answer 3

Slightly negative

Question 4

What is the charge of the hydrogens?

Answer 4

Slightly positive

Question 5

What type of molecule is water?

Answer 5

The different charged regions makes it a POLAR MOLECULE. Because it has two charged regions it is DIPOLAR.

Question 6

How do water molecules bond?

Answer 6

HYDROGEN BONDING. The slightly negative charge on the oxygen atom makes it attract to the slightly positive hydrogen atom of another water molecule.

Question 7

What do the numerous hydrogen bonds do to waters structure?

Answer 7

They make it very stable

Question 8

What is the biological importance of water?

Answer 8

Water is necessary for transport, chemical reactions, temperature control, support, movement and reproduction

Question 9

What is the structure of water?

Answer 9

H2O

Two hydrogen atoms covalently bonded to one oxygen atom

Question 10

Give an example of how water is used in transport:

Answer 10

• All transport fluids in mammals are water based (e.g: cytoplasm, blood, plasma, tissue fluid)
• uptake of minerals in soil by plants occurs in solution (in water)

Question 11

Give an example of how water is used in chemical reactions:

Answer 11

• water is the ideal environment for reactions, photosynthesis, respiration and excretion occur in solution
• water also acts as a reactant in hydrolytic reactions (e.g digestive enzymes)

Question 12

Give an example of how water is used in temperature control:

Answer 12

• water remains liquid over a huge temperature range, essential for metabolism and for aquatic organisms to avoid freezing
• when water evaporates energy is released, this is involved in cooling mechanisms

Question 13

Give and example of how water is used for support:

Answer 13

• in plants water confers turgidity essential in maintaining maximum leaf surface area, which increases light absorption in photosynthesis
• in animals water filled tissues contribute to skeletal support

Question 14

Give an example of how water is used in movement:

Answer 14

• water is involved in nastic movements, for instance the opening and closing of plants
• earthworms use their hydrostatic skeletons to move, their muscles are able to contract against the watery fluid of the coelom for them to move

Question 15

Give and example of how water is used in reproduction:

Answer 15

• organisms use water to bring make and female gametes together in the process of fertilisation
• in mammals the foetus develops in a water filled sac providing physical and thermal stability

Question 16

What are nastic movements?

Answer 16

Those not involving growth in a particular direction

The non directional response to stimulus

Question 17

What is turgidity?

Answer 17

It refers to something swollen, giving it structure. Hence why plant cells are full of water, if not they would wilt

Question 18

Why does salt (NaCl) dissolve in water?

Answer 18

The positive sodium is attracted to the negative oxygen atom in a water molecule, whilst the negative chlorine is attracted to the positive hydrogen atoms. The salt is then pulled apart (it dissolves)

Question 19

What molecules are insoluble in water?

Answer 19

Non polar molecules like lipids because they do not attract to the atoms within the water molecule

Question 20

What does it mean that water has high latent heat evaporation, what is this used in?

Answer 20

It takes a lot of energy to break the hydrogen bonds between water molecules. So a lot of energy is used up when water evaporates (high latent heat of evaporation).
Used in cooling mechanisms

Question 21

What is cohesion?

Answer 21

Attraction between molecules of the same type

Question 22

Why are water molecules very cohesive?

Answer 22

Because of their polarity - water molecules tend to stick together

Question 23

What does waters polarity help it do?

Answer 23

• flow
• making it good for transport
• all transport fluids in animals are water based (cytoplasm, blood, plasma)

Question 24

What else does waters polarity make it?

Answer 24

A good solvent