2.4- WATER AND ITS FUNCTION Flashcards
What causes water’s unusual properties?
due to its dipolar nature and subsequent hydrogen bonding it allows
What is a molecule of water made up of?
two atoms of hydrogen and one molecule of oxygen
Does a water molecule have an overall charge?
no overall charge
Where is the slight negative charge of the water molecule?
oxygen atom
Where is the slight positive charge of the water molecule?
hydrogen atoms
What can be said as the water molecule have positive and negative poles?
dipolar
Why is the positive pole of one water molecule attracted to negative pole of another water molecule?
different poles attract
What is the attractive force between opposite charges called? (for water)
hydrogen bond
How strong is each hydrogen bond?
fairly weak
Although hydrogen bonds are weak, collectively what do they form?
important forces that cause water molecules to stick together giving water its unusual properties
Why does it take more energy to separate water molecules than would be needed if they did not bond to one another?
because water molecules stick together
As more energy is needed to separate water molecules what does this mean?
boiling point of water higher than expected
What would happen to water without its hydrogen bonding?
water would be gas at temperatures commonly found on Earth
Why is more energy needed to heat a given mass of water?
as water molecules stick together
What is it called when more energy is needed to heat a given mass of water?
high specific heat capacity
What can water do as it has a high specific heat capacity?
buffer against sudden temperature variations
As water can act as a buffer against sudden temperature changes, what does it do to the aquatic environment?
makes the aquatic environment a temperature-stable one
What does water do to organisms due to its high specific heat capacity?
buffers them against sudden temperature changes especially in terrestrial environments
Why is a lot of energy to evaporate 1g of water?
due to hydrogen bonding between water molecules
What is the energy to evaporate 1g of water called?
latent heat of vaporisation
Why is evaporation of water such as sweat in mammals a very effective means of cooling?
because body heat is used to evaporate the water
What is cohesion
tendency of molecules to stick together
Why does what have large cohesive forces?
its hydrogen bonding
What is allowed as water has large cohesive forces?
allows it to be pulled up through a tube, such as xylem vessel in plants
What happens to water molecules when they meet air due to their large cohesive forces?
pulled back into body of water rather than escaping from it
What is the force called when water molecules are pulled back into the body of water rather than escaping from it?
surface tension
What does surface tension mean?
water surface acts like skin and strong enough to support small organisms
Example of small organism that surface of water able to support?
pond skaters
What percentage of jellyfish is water?
98%
What percentage of mammals are water?
65%
How is water used in metabolism? (3)
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
What substances does water readily dissolve? (4)
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
What does the evaporation of water do to organisms?
cools organisms and allows them to control their temperature
Is water easily compressed?
no
What does water do as it’s not easily compressed?
provides support
Example of how water provides support as it’s not easily compressed?
hydrostatic skeleton of animals such as the earthworm and turgor pressure in herbaceous plants
Why is water being transparent good? (2)
aquatic plants can photosynthesise
light rays can penetrate jelly-like fluid that fills eye and so reach retina
Where can inorganic ions be found in an organism?
in solution in cytoplasm and in body fluids and as part of larger molecules
In what concentrations can inorganic ions occur?
may be in concentrations that range from very high to very low
Where is iron ions found?
in haemoglobin
What role does iron ions have in haemoglobin?
role in transport of oxygen
What roles does phosphate ions have? (2)
structural role in DNA
role in storing energy in ATP molecules
What role do hydrogen ions have?
important in determining pH of solutions and so functioning of enzymes
What role do sodium ions have?
important in transport of glucose and amino acids across plasma membrane
