AINUL_H5T04A_FINAL

Kolej Matrikulasi Pulau Pinang

ASSIGNMENT: BIOLOGY SB015
MOLECULES OF LIFE & CELL
STRUCTURES AND FUNCTIONS

(QUESTION SET C)

SEMESTER 1

Name: 'Ainul Mardhiah Binti
Mohd Sharimshah

Matric No: MS2213104264
Practicum: H5T04A

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

TYPES OF MOLECULES 3) LIPIDS
OF LIFE
5) DNA & RNA
1) WATER MOLECULES

4) PROTEIN

2) CARBOHYDRATES

ii. Classify lipids into three main types based on their structure and

characteristics [15 marks]. CHO

Types of lipids dissolve in organic
solvent

TRIGLYCERIDES PHOSPHOLIPIDS STEROIDS

-CONSISTS OF 1 GLYCEROL AND 3 FATTY lecithin steroids
ACIDS
-COMPONENT OF CELL MEMBRANE -COMPONENT IN CELL MEMBRANE
-ALSO KNOWN AS TRIACYLGLYCEROL -CONTAIN NUTRIEN CHOLINE FOUND -PRECURSOR FOR SEX HORMONE
IN EGG YOLK, PEANUT, MILK, SOYA (EG:TESTOSTERONE)
fat oil BEAN.

-solid at room -liquid at room
temperature temperature

1. Formed by 3 fatty acids and 1 glycerol TRIGLYCERIDES
2. Each fatty acid joins to glycerol by
condensation reaction / -Consists of 1 glycerol and 3 fatty acids
esterification -Glycerol is a type of alcohol contains:
3. Three water molecules are removed. • 3 carbon atoms (C) & 3 hydroxyl (OH-) groups
-type of fat (lipid) found in your blood
4. The hydroxyl (OH) from carboxyl end of .-store unused calories and provide your body
fatty acid and with energy.
-High triglycerides may contribute to hardening of
hydrogen from the hydroxyl group of glycerol the arteries or thickening of the artery walls
are removed. (arteriosclerosis) which increases the risk of
stroke, heart attack and heart disease.
5. Three ester linkages are formed.
6. The first reaction yields a
monoacylglycerol/monoglyceride
7. The second reaction yields a
diacylglycerol/diglyceride
8. The third reaction yields a
triacylglycerol/triglyceride

PHOSPHOLIPIDS consist of
2 fatty acids

1 glycerol

selectively permeable 1 phosphate

Molecules that dissolve in fat can pass group

through easily, while molecules that

dissolve in water cannot pass through

easily.


in water, phospholipids tend to become

arranged with their hydrophobic tails

(water hating) facing each other and

their hydrophilic heads (water loving)

facing out.

STEROIDS

The steroid core structure has 17 carbon atoms connected with 4
fused rings in a specific way. Three of these are cyclohexanes and
one is cyclopentane system.
Insoluble in water but soluble in lipid.
Have 4 hydrocarbon ring structure with different functional side
chain which determine the types of steroid.

Example of Steroids

Cholesterol
The precursor of steroid hormones such as testosterone & estrogen.
Component of cell membrane which functions to help in maintaining

the fluidity of cell membrane.
.

glycolipid globular protein glycoprotein Plasma Membrane

carbohydrate

channel alpha helix cholesterol Fluid Mosaic Model
integral protein protein peripheral protein • Membrane is composed of 2 layers
protein
(bilayer) of phospholipids
with globular proteins embedded in the

bilayer
• Fluid: phospholipids & proteins can

move laterally (can move
side to side).

Mosaic: proteins are embedded in the
phospholipid bilayer like

the mosaic tiles embedded in mortar.

Plasma Membrane -molecules that can pass through phospholipids:
water,
Cholesterol
urea, gases: O2, CO2 and lipid soluble substances
Found between phospholipids –- molecules that cannot pass through
Function: phospholipids: ions,
Increase flexibility & stabilizes the polar and large molecules: e.g.: glucose
membrane structure by regulating the
fluidity of the membrane. PROTEIN

– Intrinsic / Integral proteins:
partially embedded or fully
embedded: transmembrane
protein

– Extrinsic / Peripheral proteins:
attached to the outer &

inner surfaces of the membrane

• Carbohydrate chain /
oligosaccharides

– Found on the external surface of
the plasma membrane

• Carbohydrate chain attaches to
protein--> glycoprotein

• Carbohydrate chain attaches to
phospholipids --> glycolipid

– Function as cell identity markers /
recognition.

iv. Explain how certain type of lipids ensures the fluidity of the plasma membrane while
some other type of lipids may reduce its fluidity [5 marks].

Cholesterol plays a distinct role in membrane Phospholipids and protein of plasma
structure. membrane can move laterally.
Cholesterol inserts into a bilayer of phospholipids They not static, thus can contribute
with its polar hydroxyl group close to the to the fluidity of membrane.
phospholipid head groups.
At high temperatures, cholesterol interferes
with the movement of the phospholipid fatty acid
chains, making the outer part of the membrane
less fluid and reducing its permeability to small
molecules.
At low temperatures, cholesterol has the
opposite effect: By interfering with interactions
between fatty acid chains, cholesterol prevents
membranes from freezing and maintains
membrane fluidity.

THANK YOU! <3