Water Flashcards
Why is water important
- it’s a metabolite in loads of different important metabolic reactions, including condensation and hydrolysis .
-water is a solvent , which means some substances dissolve in it .Most metabolic reactions take place in solution (e.g., in the cytoplasm if eukaryotic and prokaryotic cells )
-water has a high specific heat capacity and a high latent heat of vaporisation which helps with temp control
-water molecules are very cohesive which helps water transport in plants as well as transport in other organisms .
Describe the charges in a water molecule
One water atom and two hydrogen atoms .The molecule has no overall charge .However the oxygen atom has a slight negative charge and the hydrogen has a slight positive charge .Due to this water is a polar molecule and has a positive and negative pole.
How do water molecules bond with one another ?
DIFFERENT poles attract ,the positive hydrogen will be attracted to the negative oxygen .This is called a hydrogen bond .Each bond is fairly weak, together they form a strong force that caused water to stick together and in turn causes its very unusual properties .
Describe and explain the specific heat capacity of water ?
Because of the overall force of the hydrogen bonds , it takes more energy (heat ) to separate them ,this means there is less energy left to actually heat the water .this makes the boiling point of water is higher then expected (high specific heat capacity ), without the hydrogen bonds water would be a gas .Water acts as a buffer against sudden temperature variations ,this is useful for living organisms because it means water doesn’t experience rapid temp changes so organisms can maintain a fairly constant internal body temp .
Explain and describe the latent heat of vaporisation in water ?
Water evaporates when the hydrogen bonds between water molecules together are broken -this allows water molecules on the surface of the water to escape into the air as a gas .
Hydrogen bonding in water means that it requires a lot of energy to evaporate 1-gram of water .The energy is called latent heat of vaporisation .
This is usefull for mammals because it means they can use water loss through evaporation too cool down without losing too much water .
Evaporation of water such as sweat in mammals is therefore a very effective means of cooling because body heat is used to evaporate the water .
Explain and describe cohesion and surface tension in water ?
The tendency of molecules to stick together is know as cohesion .Due to its hydrogen bonding ,water has high large cohesive forces and these allow it to be pulled through a tube (e.g., Xylem vessel ) .
where water molecules meet air they tend pulled back into the body of water rather than escaping it .This force is called surface tension and means that the water surface acts like skin and is strong enough to support small organisms like pond skaters.
Explain water and metabolism ,Give examples
Water is used to break down many complex molecules by hydrolysis(which requires a water molecule to break a bond ) .For example proteins and amino acids .A molecule of water is released as a new bond is formed in condensation reactions . For example , amino acids are joined together to make polypeptides (proteins ) by condensation reactions .Energy from ATP is released through a hydrolysis reaction .
Chemical reactions take place in an aqueous solution
Water is a major raw material in photosynthesis
Explain water as a solvent and give examples of what it’s a solvent for .
-A lot of substances in biological reactions are ionic (e.g., salt ) ,this means there made from one positively charged atom or molecule and one negative (e.g., salt is made from a positive sodium ion and a negative chloride ion )
-opposite charges attract so the water molecules will completley surround a ion due to it being a polar molecule and thus dissolve .
-this means living organisms can take up useful substances (for example ,mineral ions ) dissolved in water and these dissolved substances can be transported around the body .
Examples of what water dissolves : oxygen ,carbon dioxide ,ammonia (waste) ,urea (waste ) ,inorganic ions and small hydrophilic molecules [such as amino acids ,monosaccharides and ATP],enzymes whose reactions take place in solution
