Inorganic Ions, Water, Monomers And Polymers

Question 1

Roles water plays in biology

Answer 1

Solvent- polar (slightly charged) so will dissolve any charged molecules (salt ions), other polar molecules (glucose, amino acids). Water can act as a medium for biochemical reactions in cells/ organelles.
Transport- dissolved biological molecules can be transported around organisms (blood stream in mammals and xylem/ phloem in plants). Transpiration stream in plants works because water molecules are hydrogen bonded to eachother along the entire column.
Surface tension- its cohesive and hydrogen bonds to other water molecules. This creates a surface tension on ponds and a habitat for some organisms e.g. pond skaters.
Specific heat capacity- a lot of energy is required to raise water by 1 degree and it cools slowly. Large bodies of water are thermostable (thermally stable) and buffer changes in temperature. This stabilises aquatic habitats.
High latent heat of vaporisation- due to lots of hydrogen bonding, a small volume of water requires a lot of energy to break all of these and evaporate. A small volume of water can have a big cooling effect in mammals.
Ice- ice is less dense than water because the hydrogen bonds push the molecules further apart. Floating ice thermally insulates liquid water below and provides a habitat on the surface.
Metabolite- it’s a chemical used and produced in chemical reactions. Used to make sugars in photosynthesis, used in hydrolysis and released in condensation reactions.
Transparent- enables aquatic plants to photosynthesis.

Question 2

Why is water polar (dipolar)?

Answer 2

A water molecule is made up of two atoms of hydrogen and one of oxygen. Although it has no overall charge, the oxygen has a slightly negative charge while the hydrogen atoms have a slightly positive charge. This makes the molecule polar.

Question 3

How do the charges in water molecules cause hydrogen bonding?

Answer 3

The positive pole of one water molecule will be attracted to the negative pole of the other water molecule. This attractive force between opposite charges is called a hydrogen bond. Although each bond is weak, together they form important forces that cause water molecules to stick together, giving water unusual properties.

Question 4

Define a monomer

Answer 4

Single, small soluble repeating units that can be bonded together to form a much longer chain or polymer.

Question 5

Define a polymer

Answer 5

Large, insoluble molecules (chains and/ or branches) made up from many monomers.

Question 6

Describe a condensation and hydrolysis reaction.

Answer 6

Condensation reactions make monomers into a polymer (H2O released).
Hydrolysis reactions breaks the polymer into monomers (H2O added)