Question

C1. Water Water has a number of unique properties that are essential for life. Most of these properties are as a result of the polar nature of water and its ability to form hydrogen bonds. Using your knowledge on the properties of water, answer the questions below. a) Why is it important for water to be a liquid over a broad range of temperatures? [2 marks] b) Why is water referred to as polar and why does its polarity affect its solvent properties? [2 marks] c) What two processes are involved in the transport of water from the roots to the leaves of a plant? [2 Marks] d) What is the biological importance of solid water being able to float on liquid water? [2 marks] e) Why is water's high latent heat of vaporization biologically significant? Give two reasons. [2 Marks) C2. Carbohydrates a) D-Glucose alpha-D-Glucose -Amylopectin Glycogen Sucrose. Using each carbohydrate only once from the list above, state which carbohydrate is: i. A non-reducing sugar? [1 Mark] ii. A carbohydrate containing both a beta 1-4 glycosidic bond and beta 1-6 glycosidic bond in its structure [1 Mark] iii. A cyclic monosaccharide [1 Mark] iv. A reducing sugar [1 Mark]

Answer 1

a) Why is it important for water to be a liquid over a broad range of temperatures? [2 Marks]

Water remains to be liquid over a broad range of temperatures. It is important because the water molecules can remain liquid through changes in weather or climate. This is due to the unique property of water that it has high heat capacity. Due to this, it takes a lot of energy to increase some amount of water’s temperature by certain degree that helps in regulating temperature in the environment. Like we can take example of pond water. Due to high heat capacity, temperature of water present in pond stay relatively constant indifferent atmospheric temperature from day to night

Also, the molecules of water have similar size and complexity that helps in remaining it in liquid state over Molecules of similar size and complexity remain liquid over small temperature ranges.

b) Why is water referred to as polar and why does its polarity affect its solvent properties? [2 Marks]

Water is referred to as polar because of unequal sharing of its electrons between hydrogen molecule and oxygen molecules in a bent structure (because hydrogen has partial positive charges on it and a partial negative charge present on the oxygen. So, oxygen is more electronegative, meaning that it is better than hydrogen at attracting electrons).

Polarity of water affects its solvent properties. It is because being a polar molecule, water can form charge-based attractions with other polar molecules and ions. Polarity makes water a good solvent that gives ability to water to stick to it and other substances and have surface tension due to hydrogen bonding.

c) What two processes are involved in the transport of water from the roots to the leaves of a plant? [2 Marks]

Processes that are involved in the transport of water from the roots to the leaves of a plant are

a) Root pressure

b) Cohesion force

c) Adhesive properties

d) Transpiration

d) What is the biological importance of solid water being able to float on liquid water? [2 Marks]

We know that Ice (solid water) floats on water (liquid water) because it is less dense than water. It helps in survival of life on the Earth. During winter, when surface temperature starts decreasing or lowering so that water start freezing. This freezing result in the formation of ice that float on the surface of lakes or ponds or seas. Floating ice forms a layer of insulation on the surface of the water bodies i.e. lakes or ponds or seas. Layers insulate the water present below and allow it to be in liquid state beneath it that helps in survival of aquatic life present in it.