Biology Assignment Final Assignment

Biology SB015 Assignment

Topic 1: Molecule of Life & Topic 2: Cell Structure and Function

Set C Question

Name: Neoh Shao Xin
Matric Number: MS2213104020
Practicum: H3T04A

1. State the Main Types of
molecules of life

01 Water 02 Carbohydrates

➢ Consists of an oxygen atom ➢ Composed of C , H and O atoms in the

and two hydrogen atom proportion 1:2:1 (organic compound)

➢ Water is a polar molecule ➢ Source of energy or fuel for muscle

that have opposite charges contraction and biologic work

03 Lipid 04 Protein 05 Nucleic acid

➢ Large organic compound ➢ Is called polypeptides ➢ Two types of nucleic acid
➢ Composed of C , H , O , N which is DNA and RNA
➢ Insoluble in water but soluble
and sometimes S atoms ➢ Monomer of nucleic acid is
in non polar organic solvent nucleotide
➢ Monomer of protein is
➢ Basic units of lipid is fatty acid
called amino acid
and glycerol

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

Triglycerides
Structure of triglycerides

▪ Consists of 1 glycerol and 3 fatty acids
▪ Glycerol is a type of alcohol that contains 3 carbon atoms (C) and 3 hydroxyl groups (OH-)
▪ Fatty acid consists of a long linear hydrocarbon chain (R) and a carboxyl group (-COOH)

▪ Each fatty acid joins to glycerol by condensation process. In the process, 3 water molecules are removed.
▪ The hydroxyl group (OH) from carboxyl end of fatty acid and hydrogen(H) from the hydroxyl group of

glycerol are removed.
▪ Three ester bond are formed.

▪ Fatty acid can be classified as saturated fatty acid and unsaturated fatty acid.
▪ Saturated fatty acid - No double bond between carbon atoms

- Saturated with hydrogen

▪ Unsaturated fatty acid - one or more double bond between carbon atoms
- Not saturated with hydrogen

Characteristics of triglycerides Oils (Unsaturated Fats)

Fats (Saturated Fats) • Exist as liquid at room temperature
• Has low melting point
• Exist as solid at room temperature
• Has high melting point • Has high rancidity

• Has low rancidity • Generally from fish such as fish oil or plant
source such as plant oil
• Generally from animal source such as butter
and lard

Phospholipids

Structure of Phospholipids

▪ Phospholipids is made up of 2 fatty acid, 1 glycerol and 1 phosphate
▪ Phospholipids molecule has two hydrophobic tails and one hydrophilic head
▪ Exist as double layer, called phospholipid bilayer

Characteristic of Phospholipids

▪ Act as plasma membrane components, phospholipids are selectively permeable meaning that only certain
molecules can pass through them to enter or exit the cell.

▪ Phospholipids is an amphipathic molecule, meaning it has a hydrophobic part and a hydrophilic part.
▪ Hydrophobic tails is water-hating while hydrophilic head is water-loving

Steroids

Structure of Steroids

• Steroid core structure has 17 carbon atoms connected with 4 fused rings in a specific way.
• All steroids have four linked carbon rings and several of them, like cholesterol, also have a short tail
• Functional groups attached to the rings determine the types of steroids.

Characteristic of Steroids

• Steroids are included in lipid category because they are also hydrophobic and insoluble in water.
• Cholesterol is the most common steroid - Component in plasma membrane

- Precursor for sex hormone
• Function of cholesterol is used to increase the flexibility and stabilizes the membrane structure by

regulating the fluidity of the membrane.

3.Plasma membrane of cells consists of lipids and some other
organic molecules. With the aid of diagram, briefly describe the

structure of plasma membrane.

Structure of plasma membrane

• Structure of plasma membrane is described by the Fluid Mosaic Model
• Membrane is composed of two layers of phospholipid with globular proteins embedded in the bilayer
• Fluid: Phospholipids and proteins can move laterally
• Mosaic: Proteins are embedded in the phospholipid bilayer like the mosaic tiles embedded in motar.

Organic molecules that Interpretations
involved in plasma membrane
➢ Accounted for the amphipathic characteristic
Phospholipids -Hydrophilic head (water-loving)
-Hydrophobic tail (water-hating)

➢ The hydrophilic head of phospholipids facing outwards and attracted to
the aqueous surrounding while the hydrophobic tails facing inwards

Membrane protein ➢ Integral protein (Intrinsic protein) partially embedded or fully
embedded

➢ Peripheral protein (Extrinsic protein) attached to the outer and inner
surface of membrane.

Organic molecules that involved Interpretations
in plasma membrane
➢ Carbohydrates chain attaches to phospholipids is called glycolipid
Carbohydrates chain ➢ Carbohydrates chain attaches to membrane protein is called
(Oligosaccharides)
glycoprotein
➢ Function of glycolipid and glycoprotein is act as cell identity

markers or recognition

Glycolipid Glycoprotein

Cholesterol ➢ Found between phospholipids
➢ At moderately warm temperature, cholesterol reduce membrane

fluidity by preventing free movement of phospholipid molecules
➢ At cool temperatures, cholesterol prevent close packing of

phospholipids and slow down the solidification

4. Explain how certain type of lipids ensures the fluidity of the plasma
membrane while some other type of lipids may reduce its fluidity

• Saturated fatty acid and unsaturated fatty acid may affect the fluidity of plasma membrane.
• Saturated fatty acids are chains of carbon atoms that have only single bonds between them.

As a result, the chains are straight and easy to pack tightly.
• Unsaturated fats are chains of carbon atoms that have double bonds between some of the

carbons. The double bonds create kinks in the chains, making it harder for the chains to pack
tightly.
• These kinks play a role in membrane fluidity because they increase the space between the
phospholipids, making the molecules harder to freeze at lower temperatures.
• Phospholipid and protein in the plasma membrane also can affect the fluidity of plasma
membrane.
• Phospholipid and proteins can move laterally. They are not static but dynamic. This provide
fluidity of the plasma membrane.

• Cholesterol also may affect the fluidity of plasma membrane.
• Cholesterol reduce membrane fluidity by preventing free movement of phospholipid molecules at

moderately warm temperature.
• Cholesterol prevent close packing of phospholipids and slow down the solidification at cool temperatures.

Thank You !