Biological molecules Flashcards
What is water composed of?
Atoms of hydrogen and oxygen. One atom of oxygen combines with two atoms of hydrogen by sharing electrons (covalent bonding)
What is the charge of the other side of each hydrogen atom?
Because the shared negative hydrogen electrons are pulled towards the oxygen atom, the other side of each hydrogen atom is left with a slightly positive charge.
What is the charge of the oxygen and why?
The unshared negative electrons on the oxygen atom give it a slight negative charge.
What makes water polar molecule?
It has a partial negative charge on one side and a partial positive charge on the other.
What do the slightly negatively-charged oxygen atoms attract?
The slightly positively charged hydrogen atoms of other water molecules. This attraction is called hydrogen bonding and it gives water some of its useful properties.
What is specific heat capacity?
The amount of thermal energy required to raise the temperature of 1g of that substance by 1°C.
Why does water have a high specific heat capacity?
Due to the many hydrogen bonds present in water. It takes a lot of thermal energy to break these bonds and a lot of energy to build them, thus the temperature of water does not fluctuate greatly.
What is the advantage for living organisms of water having a high specific heat capacity?
- Provides suitable habitats
- Is able to maintain a constant temperature as water is able to absorb a lot of heat without big temperature fluctuations.
-> this is vital in maintaining temperatures that are optimal for enzyme activity.
Why does water have a high latent heat of evaporation?
Because a large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate.
How is water having a high latent heat of evaporation an advantage?
Only little water is required to evaporate for the organism to lose a great amount of heat.
-> This provides a cooling effect for living organisms, for example the transpiration from leaves or evaporation of water in sweat on the skin.
Why is water a good solvent?
Many important substances in biological reactions are ionic (e.g. salt). This means they’re made from one positively-charged atom or molecule and one negatively- charged atom or molecule (e.g. salt is made from a positive sodium ion and negative chloride ion).
Because water is polar, the slightly positive end of water will be attracted to the negative ion, and the slightly negative end of the water molecule will be attracted to the positive ion. Meaning that the ions will get totally surrounded by water molecules.
Why is water being a solvent good?
Allows chemical reactions to occur within cells (as dissolved solutes are more chemically reactive when they are free to move about).
And metabolites can be transported efficently (except non-polar molecules which are hydrophobic).
Why is water cohesive?
The strong hydrogen bonds between the water molecules allows for strong cohesion between water molecules. (Because they are polar)
Why is water being cohesive useful?
Allows columns of water to move through the xylem of plants and through blood vessels in animals.
Why is water less dense when it freezes (when it is solid)?
Because the water molecules are held further apart in ice than they are in liquid water because each water molecule forms 4 hydrogen bonds to other molecules, making a lattice shape. This makes ice less dense than liquid water- which is why ice floats.
Why is water being less dense when it is a solid useful for organisms?
Because in cold temperatures, ice forms an insulating layer on top of water- the water below does not freeze. So organisms that live in water, like fish, don’t freeze and can move around freely.
What percentage of cells content’s does water make up?
80%
What is a monomer?
Smaller units from which larger molecules are made
