Water-biological molecules

Question 1

angle between O and H ball and stick diagram

Answer 1

104.45

Question 2

Why is the oxygen end of the molecule slightly negative

Answer 2

-due to unbonded electrons

Question 3

why is the hydrogen end of molecule slightly positive

Answer 3

• no electrons near as they are bonded with oxygen

- closer to a positive nucleus

Question 4

Why is the molecule dipolar

Answer 4

-because of the differences in charge

Question 5

What are hydrogen bonds

Answer 5

-intermolecular attractions between the molecules

Question 6

formation of hydrogen bond

Answer 6

• water molecules are dipolar
• weakly positive side of the hydrogen atom, due to positive nucleus, attracted to the weakly negative side of the oxygen atom due to exposed electrons
• creates hydrogen bond between oxygen of 1 molecule and the adjacent hydrogen atom

Question 7

4 main properties of water

Answer 7

• acts as a solvent
• high specific heat capacity
• low density solid
• cohesion and adhesion

Question 8

relevance of water being a solvent in nature

Answer 8

• dissolves solutes in an organism e.g mineral ions in plants, many solutes are polar molecules
• transports material e.g glucose in blood and mineral ions up xylem
• medium for chemical reaction in body
• cytosol of prokaryotes and eukaryotes is mainly water

Question 9

relevance of water having high specific heat capacity in nature

Answer 9

• stable temp provides a constant environment for aquatic animals e.g fish
• acts as a coolant helping to reduce temp changes during chemical reactions due to the amount of energy required to overcome hydrogen bonds

Question 10

relevance of water being a low density solid in nature

Answer 10

• floats on water
• ice provides habitats and acts as an insulating layer to organisms below
• surface tension supports small insects
• changes in density with temp causes currents to circulate nutrients

Question 11

relevance of cohesion and adhesion in water in nature

Answer 11

• cohesion between water molecules means they stick together when transported through the body
• water can rise up a narrow tube e.g xylem against the force of gravity due to adhesion and cohesion exhibiting capillary action
• aids water with being a transport medium

Question 12

diff between cohesion and adhesion

Answer 12

cohesion=attraction between water molecules

adhesion=attraction with other materials e.g xylem vessel walls

Question 13

relevance of water having a high latent heat of evaporation

Answer 13

• a lot of energy is used up when water evaporates

- many mammals sweat when theyre too hot, when sweat evaporates, it cools the skin.

Question 14

why is water a good solvent

Answer 14

-water is polar, the slightly positive end of the water molecule will be attracted to the negative ion (and vice versa), allowing it to dissolve in it as it will be surrounded by the water molecules

Question 15

why is ice less dense than water

Answer 15

-each water molecule forms 4 hydrogen bonds to other water molecules, making a lattice=makes it less dense than water

Question 16

definition of specific heat capacity

Answer 16

the energy needed to raise the temp of 1 gram of a substance by 1C

Question 17

why does waters polarity make it a good solvent

Answer 17

many important substances in biological reactions are ionic e.g salt
-the slight negative end of water molecule will be attracted to positive ion and vice versa= ions will get surrounded by water molecules ie they dissolve

Question 18

why is ice less dense than liquid water

Answer 18

each water molecule forms 4 hydrogen bonds to other water molecules, making a lattice

Question 19

List three other examples of where hydrogen bonds are found in biological molecules.

Answer 19

protein secondary structure / α-helix / -pleated sheet ;
(protein) tertiary structure ;
between polypeptide chains in (named) quaternary
structure ;
(between chains of) cellulose ;
(between, strands of / bases in) DNA ;
AVP