Biological molecules: water Flashcards
Molecules are polar when…
there are regions of positivity and negativity
Why is water a polar molecule?
because oxygen has a greater share of electrons than hydrogen in the O-H bond
How do hydrogen bonds act in water?
the positive and negative regions of the molecules attract, this is hydrogen bonding. It is weak and constantly breaks and reforms between moving water molecules.
1st property: high boiling point even though water is a small molecule
due to hydrogen bonding
2nd property: ice can float on water as it is less dense. why? How does it help for living organisms?
because hydrogen bonds fix the positions of polar molecules slightly further apart than average in liquid state. This produces an open crystal lattice structure, making it less dense. Ice provides a habitat and is also acts as an insulating layer allowing the temp of water below to be constant so organisms below don’t freeze.
3rd property: water is cohesive and adhesive.
due to hydrogen bonds, water molecules stick together(cohesion). Water is adhesive as it also sticks to other materials.
How does cohesion and adhesion in water support life?
cohesion and adhesion allows water to travel up the xylem and body creating a capillary action. This makes water an efficient transport medium. Cohesion also causes surface tension where water meets air allowing it to act as a habitat.
4th property: high specific capacity
A large amount of energy is needed to change the temp, therefore the temp doesn’t change rapidly. This means organisms can live in water as the temp is constant which is important for enzyme activity.
5th property: high latent heat of vaporisation. How does this help for life?
This means it take water a large amount of energy to evaporate. This allows animals to cool without losing too much water. E.g sweating where heat energy is used to evaporate water from the skin, the transfer of heat allows organisms to cool
6th property: good polar solvent. How does this help for life?
water acts as a polar solvent due to the hydrogen bonds. Water and cells contain many dissolved substances. Water also helps transport substances, making it a good transport medium.
why is the ability of water to act as a solvent important for the survival of organisms?
1)organisms can ABSORB minerals and ions
2) able to dilute toxic substances
3)acts as a transport medium
why is it important to keep water at a constant temperature?
organisms spend less energy on temperature control and so water below doesnt freeze.
List three examples of biological molecules where hydrogen bonds are found?
-proteins
-cellulose
-DNA
Explain how properties of water are related to the transport role of water in a stem?
-adhesion allows capillary action, not cohesion
-cohesion allows water molecules to stick together
-adhesion allows water to stick to xylem vessels
