Assignment biology(ain)

MOLECULE OF LIFE & CELL
STRUCTURE AND FUNCTIONS.

o Name:Siti Nur’Ain Binti Hasbullah
o Matric number: MS2113173535
o Practicum: K4T01B
o Lecturer’s name: Aniza Binti Abu Bakar

SET A:
WATER

State the main types of molecules of life

[5 marks]

WATER DNA and RNA
MOLECULES
Types of
molecule of

life.

CARBOHYDRATES PROTEINS

LIPIDS

WITH THE AID OF A LABELED DIAGRAM,DESCRIBE
THE STRUCTURE OF WATER MOLECULE.

[10 marks]

A water molecule contains an oxygen atom two hydrogen atoms.Two hydrogen atoms
form polar covalent bonds (sharing of electrons) with an oxygen atom.

Water is a polar molecule.A polar molecule have opposite charges(unequal distribution of
electrical charge.In the covalent bond, oxygen pulls the electrons closer towards its
nucleus.This gives oxygen a partial negative charge and hydrogen a partial positive
charge,since electrons have a negative charge.

A water molecule has a V shape between the two hydrogen atom at 104.5° angle.Water
molecule are held together by a hydrogen bond.It formed when a hydrogen atom is

attracted to another strongly electronegative atom.A partial positive hydrogen of in H2O
molecule is attracted to the partial negative oxygen of nearby H2O molecule.Each water
molecule can form hydrogen bonds with up to maximum 4 other molecules.Hydrogen
Diagram 1:Structure of water molecule bonds are weaker than covalent bonds but they are strong enough to hold H2O molecules

together.

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]

Evaporation of water in sweat on a skin as heat is removed will give a cooling effect. When our
body temperature begins to rise, we sweat.Evaporation of sweat uses a lot of heat energy.This energy
has a cooling effect to the skin and helps prevent overheating.Water is critically important for just about
every organ in your body. This means that when we sweating, we also need to make sure our drinking
plenty of water so we can replace the water we lose with water we can use.As our excess body heat is
used to convert beads of sweat into vapor, we start to cool down.

While as elephants,its do not sweat will bathe or wet themselves with water to prevent their bodies
from overheating during hot days.Evaporation cooling.In hot weather, an elephant sprays water from its
trunk onto its head.Evaporation of this water cools the elephant down.Water molecules with the greatest
kinetic energy leave as gas,making the remaining liquid water cooler.This is because water has high
latent heat of vaporisation.High amount of heat energy is required or absorbed to turn 1 g of water
from liquid state into water vapor.This is to break hydrogen bonds to separate water molecules.

WATER MOLECULES MOVE INTO OR OUT OF CELLS THROUGH
OSMOSIS.EXLAIN ON OSMOSIS AND COMPARE IT WITH THE OTHER

TYPES OF PASSIVE TRANSPORT.
[10 marks]

Osmosis is a passive transport process that the a movement of water molecules from higher water
potential region to lower water potential region across a selectively permeable membrane until equilibrium
is reached.Water potential is the term given to the tendency for water molecules to enter or leave the
solution by osmosis.A measure of the free kinetic energy of water molecules in solution.Pure water has
the highest water potential is zero.Any solution has negative water potential value.Effect of dissolving
solute molecules into pure water is to reduce the concentration of water molecules-water potential gets
lower.Water diffuses from region of high water potential to a region of lower water potential.

OSMOSIS VS DIFFUSION.

DIFFUSION

OSMOSIS SIMPLE DIFFUSION FACILIATED DIFFUSION

SIMILARITIES  Both are passive transport.  Molecule move  Molecule move
DIFFERENCES  No energy is required. down its down its
 Both cannot be controlled by the cell. concentration concentration
gradient. gradient.
 Water molecule from higher water
potential region to lower water
potential region.

 Water moves through phospholipid  Water moves  Water moves
bilayer and aquaporin.
through through

phospholipid bilayer channel/carrier

only. protein.

 Happens to water for the movement of  Happens to the  Happens to large or
particles. small and non-polar polar particles.
particles.

THANK YOUUU