topic 1 - water Flashcards
cgp (topic 1B) 20 - 21
name four functions of water
(1) it’s a metabolite in many important metabolic reactions
(2) it’s a solvent
(3) helps with temperature control as it has a high latent heat of vaporisation and a high specific heat capacity
(4) water molecules are very cohesive - help water transport in plants as well as transport in other organisms
what is a metabolic reaction
a chemical reaction that happens in a living organism to keep the organism alive
what forms a molecule of water
one atom of oxygen (O) joined to two atoms of hydrogen (H2) by shared electrons
what is a polar molecule
a molecule which has a partial negative charge on one side and a partial positive charge on the other
why is water a polar molecule
because the shared negative hydrogen electrons are pulled towards the oxygen atom - the other side of each hydrogen atom is left with a slight positive charge - the unshared negative electrons on the oxygen atom give it a slight negative charge
what is the hydrogen bonding in water
the slightly negative charged oxygen atoms attract the slightly positively charged hydrogen atoms of other water molecules
how is water an important metabolite
many metabolic reactions involve a condensation or hydrolysis reaction - a hydrolysis reaction requires a molecules of water to break a bond - a condensation reaction released a molecules of water as a new bond is formed
how does water have a high latent heat of vaporisation
water has a high latent heat of vaporisation so it takes a lot of energy (heat) to break the hydrogen bonds between water molecules
how is water having a high latent heat useful, give an example
this is useful for living organisms because is means they can use water loss through evaporation to cool down without losing too much water - e.g humans sweat to cool down
how does water buffer (resist) changes in temperature
hydrogen bonds between water molecules can absorb a lot of energy so water has a high specific heat capacity
how is water buffering changes in temperature useful
it means that water doesn’t experience rapid temperature changes - this makes water a good habitat because the temperature under water is likely to be more stable than on land - the water inside organisms also remains at a fairly stable temperature - helping them to maintain constant internal body temperature
how is water a good solvent
waters polarity makes it a useful solvent as many important substances in metabolic reactions are ionic meaning they’re made from one positively charged atom or molecule and one negatively charged atom or molecule - since water is polar the positive end of a water molecule will be attracted to the negative ion and the negative end of a water molecule will be attracted to the positive ion
what is cohesion
the attraction between molecules of the same type
why are water molecules very cohesive
because they’re polar
give two ways strong cohesion between water molecules helpful
(1) it helps water to flow - making it great for transporting substances - for example how water travels in columns up the xylem in plants
(2) strong cohesion means high surface tension when it comes into contact with air
