2.4- WATER AND ITS FUNCTION

Question 1

What causes water’s unusual properties?

Answer 1

due to its dipolar nature and subsequent hydrogen bonding it allows

Question 2

What is a molecule of water made up of?

Answer 2

two atoms of hydrogen and one molecule of oxygen

Question 3

Does a water molecule have an overall charge?

Answer 3

no overall charge

Question 4

Where is the slight negative charge of the water molecule?

Answer 4

oxygen atom

Question 5

Where is the slight positive charge of the water molecule?

Answer 5

hydrogen atoms

Question 6

What can be said as the water molecule have positive and negative poles?

Answer 6

dipolar

Question 7

Why is the positive pole of one water molecule attracted to negative pole of another water molecule?

Answer 7

different poles attract

Question 8

What is the attractive force between opposite charges called? (for water)

Answer 8

hydrogen bond

Question 9

How strong is each hydrogen bond?

Answer 9

fairly weak

Question 10

Although hydrogen bonds are weak, collectively what do they form?

Answer 10

important forces that cause water molecules to stick together giving water its unusual properties

Question 11

Why does it take more energy to separate water molecules than would be needed if they did not bond to one another?

Answer 11

because water molecules stick together

Question 12

As more energy is needed to separate water molecules what does this mean?

Answer 12

boiling point of water higher than expected

Question 13

What would happen to water without its hydrogen bonding?

Answer 13

water would be gas at temperatures commonly found on Earth

Question 14

Why is more energy needed to heat a given mass of water?

Answer 14

as water molecules stick together

Question 15

What is it called when more energy is needed to heat a given mass of water?

Answer 15

high specific heat capacity

Question 16

What can water do as it has a high specific heat capacity?

Answer 16

buffer against sudden temperature variations

Question 17

As water can act as a buffer against sudden temperature changes, what does it do to the aquatic environment?

Answer 17

makes the aquatic environment a temperature-stable one

Question 18

What does water do to organisms due to its high specific heat capacity?

Answer 18

buffers them against sudden temperature changes especially in terrestrial environments

Question 19

Why is a lot of energy to evaporate 1g of water?

Answer 19

due to hydrogen bonding between water molecules

Question 20

What is the energy to evaporate 1g of water called?

Answer 20

latent heat of vaporisation

Question 21

Why is evaporation of water such as sweat in mammals a very effective means of cooling?

Answer 21

because body heat is used to evaporate the water

Question 22

What is cohesion

Answer 22

tendency of molecules to stick together

Question 23

Why does what have large cohesive forces?

Answer 23

its hydrogen bonding

Question 24

What is allowed as water has large cohesive forces?

Answer 24

allows it to be pulled up through a tube, such as xylem vessel in plants

Question 25

What happens to water molecules when they meet air due to their large cohesive forces?

Answer 25

pulled back into body of water rather than escaping from it

Question 26

What is the force called when water molecules are pulled back into the body of water rather than escaping from it?

Answer 26

surface tension

Question 27

What does surface tension mean?

Answer 27

water surface acts like skin and strong enough to support small organisms

Question 28

Example of small organism that surface of water able to support?

Answer 28

pond skaters

Question 29

What percentage of jellyfish is water?

Answer 29

98%

Question 30

What percentage of mammals are water?

Answer 30

65%

Question 31

How is water used in metabolism? (3)

Answer 31

water used to break down many complex molecules by hydrolysis e.g. proteins to amino acids
water produced in condensation reactions

chemical reactions take place in aqueous medium

water is major raw material in photosynthesis

Question 32

What substances does water readily dissolve? (4)

Answer 32

gases i.e. oxygen and carbon dioxide

wastes i.e. ammonia and urea

inorganic ions and small hydrophilic molecules i.e. amino acids, monosaccharides and ATP

enzymes, whose reactions take place in solution

Question 33

What does the evaporation of water do to organisms?

Answer 33

cools organisms and allows them to control their temperature

Question 34

Is water easily compressed?

Answer 34

no

Question 35

What does water do as it’s not easily compressed?

Answer 35

provides support

Question 36

Example of how water provides support as it’s not easily compressed?

Answer 36

hydrostatic skeleton of animals such as the earthworm and turgor pressure in herbaceous plants

Question 37

Why is water being transparent good? (2)

Answer 37

aquatic plants can photosynthesise

light rays can penetrate jelly-like fluid that fills eye and so reach retina

Question 38

Where can inorganic ions be found in an organism?

Answer 38

in solution in cytoplasm and in body fluids and as part of larger molecules

Question 39

In what concentrations can inorganic ions occur?

Answer 39

may be in concentrations that range from very high to very low

Question 40

Where is iron ions found?

Answer 40

in haemoglobin

Question 41

What role does iron ions have in haemoglobin?

Answer 41

role in transport of oxygen

Question 42

What roles does phosphate ions have? (2)

Answer 42

structural role in DNA

role in storing energy in ATP molecules

Question 43

What role do hydrogen ions have?

Answer 43

important in determining pH of solutions and so functioning of enzymes

Question 44

What role do sodium ions have?

Answer 44

important in transport of glucose and amino acids across plasma membrane