DRAFT ASSIGNMENT BIOLOGY (SB015)

PENANG MATRICULATION COLLEGE
BIOLOGY
SB015

SEMESTER I, SESSION 2022/2023

MOLECULES OF LIFE & CELL STRUCTURES
AND FUNCTIONS

(SET A)

NAME : NUR NADIATUL SYAFIQA BINTI SALLEH

MATRIC NUMBER : MS2113172728

PRACTICUM : H1T02A

1. STATE THE MAIN TYPES OF MOLECULES OF LIFE. (5 MARKS)

• Water • Carbohydrates

• Lipids • Proteins

• DNA and
RNA

molecules

2. WITH THE AID OF A LABELED DIAGRAM, DESCRIBE THE STRUCTURE

OF WATER MOLECULE. (10 MARKS)

A water molecule consists of an oxygen atom and two hydrogen atoms. Each two
hydrogen atoms form polar covalent bond by sharing electrons with an oxygen
atom. Water is known as a polar molecule because it have opposite charges
(unequal distribution of electrical charge). Oxygen region has a partial negative
charge (∂ˉ) and both the hydrogen regions have a partial positive charge (∂+).
The angle between the 2 hydrogen atoms is 104.5˚ where 3 atoms form a wide V
shape, but not a straight line. Water molecules also held together by a hydrogen
bond are formed when a hydrogen atom is attracted to another strongly
electronegative atom such as F, O & N. A partial positive (∂+) hydrogen of one
H2O molecule is attracted to the partial negative (∂ˉ) oxygen of nearby H2O
molecule. Each water molecule can form hydrogen bonds with up to maximum 4
other water molecules because hydrogen bonds are weaker than covalent bonds
but they are strong enough to hold H2O molecules together.

3. BODY TEMPERATURE MAY RISE DURING HOT DAYS. HOW CAN SWEATING HELP TO GIVE
COOLING EFFECT OF OUR BODY? WHAT ABOUT ANIMALS THAT DO NOT SWEAT SUCH AS
ELEPHANTS? GIVE THE EXPLANATION BY APPLYING THE CONCEPT RELATED TO THE
PROPERTIES OF WATER. (10 MARKS)

Sweating can help to give cooling effect of our body by applying the concept related to the
properties of water which are has high latent heat of vaporisation. As soon as our body internal
temperature starts rising, our hypothalamus (a small region in our brain) tells eccrine sweat
glands distributed all over our body that it is time to start cooling down by producing sweat.
Some of this sweat has to evaporate off our skin for this process to actually work. That is
because cooling our body via sweating relies on ‘heat of vaporisation’. It takes energy to
evaporate sweat off of our skin, and that energy is heat. As our excess body heat is used to
convert beads of sweat into vapour, we start to cool down. Releasing heat through beads of
sweat that can easily evaporate off the skin is a very effective way of cooling our body down.
Evaporation of water in sweat on skin as heat is removed will give a cooling effect.

• For elephants, they use their ears to help their cooling. The surface
area of large elephants ears serves as a heat radiator. In hot
weather, elephants increase the blood supply to the ears and flap
them around to lose body heat.

4. 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 SIMPLE DIFFUSION/DIFFUSION FACILITATED DIFFUSION

• Osmosis is a movement of water • Simple diffusion is a movement of • Facilitated diffusion is a movement
molecules from higher water
potential region to lower water molecules down its concentration of charged (Na+, K+), polar
potential region across a
selectively permeable membrane gradient (without using energy/ATP (glucose, amino acid) or
until equilibrium is reached.
through a selectively permeable hydrophobic molecules down its

membrane until equilibrium is concentration gradient without

reached). using energy/ATP through

selectively permeable membrane

aided by transport protein

(carrier/channel protein) until

equilibrium is reached.

• There are 3 types of solution : • Characteristic of molecules that can • Solutes that bind to carrier protein :
-Isotonic solution
-Hypertonic solution pass through the membrane : -Polar molecules (glucose & amino
-Hypotonic solution
-Small acid)

-Non-charged • Solutes that move through channel

-Hydrophobic protein:

-Charged molecules (K+, Na+, Ca2+,

Clˉ & HCO3ˉ)