Biology Assignment

MOLECULES OF LIFE & CELL
STRUCTURES AND
FUNCTIONS

Name : Lew Lee Yee
Matric Number : MS2213103878
Practicum : H7T04A

Set A Questions

i. State the main types of molecules of life. [5 marks]

1. Water 1. 2. 5.
2. Carbohydrates
3. Lipids

4. Proteins
5. Nucleic acid

3. 4.

ii. With the aid of a labeled diagram, describe the structure of water

molecule. [10 marks]

- Water molecules consist of an oxygen atom and two hydrogen atoms.
- Two hydrogen atoms form polar covalent bonds with an oxygen atom.
- Two covalent bonds form an angle of 104.5° to each other.
- So, the water molecule is bent.

- Due to high electronegativity of oxygen, the hydrogen atom has a partial positive
charge ( +) and the oxygen atom has a slightly negative charge ( − ).
- Electrical attraction that occurs between the partial positive and negative charges on
water molecules forms a hydrogen bond.
- Each water molecules can form hydrogen bonds with up to maximum 4 other water
molecules.

Hydrogen bond

iii. Body temperature may rise during hot days. How can sweating help
to give cooling effect for our body? What about animals that do not
sweat such as elephants? Give explanation by applying the concept
related to the properties of water [10 marks].

- As the sweat evaporates, it pulls heat away from the body.
- Water has a high heat of vaporisation.
- Large amounts of heat are needed to evaporate water, because the hydrogen bonds need to be
broken to separate the water molecules from other molecules in a liquid.
- Water molecules are evaporated and become a vapor molecule.
- Heat energy is used up to evaporate sweat off of your skin, our body starts to cool down and
the cooling effect helps prevent overheating.

- Animals like elephants are lack of sweat glands.
- Animals that do not sweat will bathe or wet themselves with water to prevent their bodies
from overheating during hot days.
- In hot weather, an elephant sprays water from its trunk onto its head.
- Evaporation of this water colds the elephant down as heat energy is used up to evaporate
water.

iv. Water molecules move into or out of cells through osmosis. Explain
on osmosis and compare it with the other types of passive transport
[10 marks].

- Osmosis is the net movement of water molecules from a region of higher water
potential to a region of lower water potential through a selectively permeable membrane.
- A selectively permeable membrane only allows free movement of certain molecules
across it, and prevents or limits the movement of other substances.

- Water will move to make the concentrations the same on both sides of the membrane.
- When there are lots of water molecules (in a dilute solution) on one side of a selectively
permeable membrane compared to the other side (in a concentrated solution), water molecules
will move from the dilute to the concentrated solution until dynamic equilibrium is achieved.

Similarities & Differences :

THANK YOU !