Unit 2

Biological Molecules

LEARNING OUTCOME NUMBER 2.1:

Describe the structure and functions of carbohydrates (a biologicalmolecules)

INFORMATION SHEET 2.1

CARBOHYDRATES
Learning Objectives:
After reading this information sheet, you should be able to:
• Describe the different structure and functions of carbohydrates (a biological
molecules);
• Describe the difference among the three types of carbohydrates; and
• Explain the role of carbohydrates in specific metabolic processes.

Lesson 2.1 Carbohydrates

All organisms contain set of chemicals such as the CHONPS (carbon-hydrogen-
oxygen nitrogen-phosphorus-sulfur) that is needed for continuity of life. Large
molecules like carbohydrates, lipids, proteins and nucleic acids are important to
perform specific and unique functions in the cell. These four large molecules are the
biomolecules present in living organism.

Of the four biomolecules of life, three are considered macromolecules-carbohydrates,

proteins and nucleic acids because these macromolecules are large molecules
composed of chain-like molecules called polymers. Polymers are long molecules
having similar identical building blocks. These building blocks are smaller molecules
called monomers.

Carbohydrates
It occurs abundantly in nature. It is said that carbohydrates can also be found in
bacterial cell wall, the exoskeleton of many insects and the fibrous cellulose of plants.
According to (Khowala, 2008) 75% of the dry weight plants is carbohydrate in nature.
It also has many functions like storage form of energy in the body and providing
significant functions of the dietary calories for organism. Carbohydrates is a general
name for sugars, cellulose and starches. The empirical formula of simpler
carbohydrates is (CH2O)n. Carbohydrates are the sources of energy. They are
composed of carbon-hydrogen-oxygen ratio1:2:1.

Carbohydrate literally means “hydrated carbon”.

The Structures and Function of Carbohydrates

There are three main types of carbohydrates: monosaccharides, disaccharides and

polysaccharides. These types of carbohydrates depend on the number of sugar it
contains. Each type has a different function from others.

Monosaccharides-The simple sugar.

Chemist refers to carbohydrates as saccharides after the smaller unit from which they
are built. The monomers of carbohydrates are called monosaccharides. It is
composed of only one sugar unit and cannot be broken down into simpler sugar. It can
be classified according to the number of carbon atoms.
The most important monosaccharides are glucose, galactose and fructose.

Since monosaccharides are simple sugars, they provide energy to the organism. Foods
that are rich in sugar and fructose like fruits are the best sources of energy for people
who are drained and tired.

Figure 2.1-1 Examples of Monosaccharides

Adapted from: https://www.nutrientsreview.com/carbs/monosaccharides-simple-sugars.html

Disaccharides
Composed of two monosaccharides unit
joined together through a process called
condensation reaction. Disaccharides are
sweet and soluble in water.
Examples:
1. Lactose (Galactose and Glucose) –
the milk sugar, a great source of nutrients
for
infants. It is used in many processed dairy
products.
2. Sucrose (Glucose and Fructose) – the
table sugar, is used as sweeteners to make
candies, ice cream, cakes and cookies and
preserved foods.
3. Maltose (Glucose and Glucose) – the
beer sugar, least sweet and it is not a
common sweetener.

Figure 2.1-2. Examples of Disaccharides

Adapted from: https://byjus.com/chemistry/disaccharides/
Polysaccharides

Are composed of many sugar building blocks. It is

not sweet. Carbohydrates that have three to ten
monosaccharides units are called oligosaccharides.
The most common polysaccharides are starch,
glycogen and cellulose. They differ in the way
glucose units are attached. Most polysaccharides are
used for energy storage. In plants, energy storage is
in the form of starch and in animals, energy storage
is in the form of glycogen.

Reflect Upon (page 102 of your book, General

Biology 1 Second Edition)
Excessive intake of carbohydrates-rich food have
been linked to obesity and other diseases. What steps
should you take so that you don’t over indulge on
cakes, pastries, pancakes, and candies?

__________________________________________
__________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

What Have I Learned So Far?

1. Identify foods that are rich in carbohydrates? For each food that you will list, tell
whether it is a source of good or bad carbohydrates?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
2. What is your basis for distinguishing good carbohydrates from bad carbohydrates?

_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

3. What are the symptoms of carbohydrate deficiency?

_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

Self-Check 2.1
Test I. Modified True or False
Direction: Read and understand the statements below. Write TRUE if the
statement is correct, if FALSE; underline the word that made it incorrect. Then, write
the correct word before the number.
_________________ 1. The three macromolecules of life are proteins, lipids and
nucleic acid.
_________________ 2. According to Khowala, 2008, 75% of the dry weight of plants
is carbohydrate in nature.
_________________ 3. Monomers are long molecules having many similar or
identical building blocks.
_________________ 4. Carbohydrates is a general name for sugars, starches and
cellulose.
_________________ 5. Monosaccharides are simple sugar consisting of two
saccharides.
_________________ 6. Hexose contains 5 carbon atoms.
_________________ 7. Disaccharides are composed of two monosaccharides unit
joined together through a process called condensation reaction.
_________________ 8. Lactose is the milk sugar composed of galactose and glucose.
_________________ 9. Polysaccharides are composed of many sugars.
_________________ 10. The most common polysaccharides are maltose, starch and
glycogen.

INFORMATION SHEET 2.2

LIPIDS
Learning Objectives:
After reading this information sheet, you should be able to:
• Describe the structure and functions of lipids as biological molecules;
• Describe the different types of lipids; and
• Explain the role of lipids in specific metabolic processes.
Lesson 2.2 Lipids
Lipids are hydrophobic molecules containing chains of hydrocarbon. It is the
collective name for fats, oils, waxes and fat-like molecules found in the body.
Hydrocarbons are organic compounds that are made up of carbon and hydrogen
and are insoluble in water. Lipids serve as insulation keeping the body warm and they
are long-term energy storage. Animals that live in polar regions have bodies with
thick layer of fats like polar bears, penguins and reindeer. The basic unit of lipids is
triglyceride which can be synthesized from a glycerol and fatty acids.

Lipids has four different types such as triglycerides, phospholipids, steroids and
waxes. Each of these has its unique function in organisms.

Triglycerides
They generally known as fats containing
a glycerol attached to three fatty acids.
Fatty acid is composed of a long chain
of carbon atoms connected to carboxylic
acid (-COOH). It has two different types,
the saturated and unsaturated fats.
Saturated fats contain only single
bonds in the fatty acid chain. It is solid
at normal temperature. A fat made from
saturated fatty acids is called saturated
fats. Most animal fats are saturated like
pork and beef. Also found in butter,
cheese and cream.

Figure 2.2-1. Structure of Saturated and Unsaturated Fatty Acid

Adapted from: https://dlc.dcccd.edu/biology1-3/lipids

Unsaturated fats, mostly known as oils containing one or more double bonds in
the fatty acid chain. The fats of plants and fish are unsaturated. Plants and fish fats are
referred to as oils, coconut and olive oils are examples.
Fats are the major storage form of fuel.

Figure 2.2-3. Saturated and Unsaturated Fats

Phospholipids
They are fat molecules that has only two fatty
acids attached to glycerol. The third hydroxyl
group pf glycerol is joined to a phosphate
group.

Figure 2.2-5. Facts About Fats

Adapted from: https://www.eufic.org/en/whats-
in food/article/8-facts-on-fats

Figure 2.2-4. Phospholipid Structure

Adapted from: https://courses.lumenlearning.com/introchem/chapter/phospholipids/

Steroids
Steroids are hormones produced in our bodies that help control inflammation, regulate
immune system, and control the development of sexual characteristics. Steroids have
four fused carbon rings.

Figure 2.2-6. Structure of Some Steroids

Adapted from: https://www.britannica.com/science/aldosterone
Cholesterol
It is a sterol (steroid alcohol), one of the most common forms of steroids. It is a
steroid alcohol (C27H45OH) that is present in animal cells and body fluids, regulates
membrane fluidity and functions are precursor molecule in various metabolic
pathways. Sex hormones are also steroids. Testosterone for male, progesterone and
estrogen for female.

Waxes
Waxes are esters (carboxylic derivatives), which are combined from certain alcohols
and fatty acid. The upper part of the leaves contains a waxy material called cuticle.
This cuticle prevents the excess loss of water. The furs and feathers also have wax to
repel water. The cerumen (earwax) helps to prevent the entry of some foreign
materials into the ear canal.

Reflect Upon

1. At your age, you tend to try different foods from fast food chains. Sometimes, you
eat so much of these foods such that you go beyond RDA for nutrients such as
carbohydrates and salt. What can you do so that you don’t overeat when you go to fast
food chains? What advise can you give your friends regarding eating out at fast food
chains?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

Self-Check 2.2
Test I. Multiple Choice
Direction: Read and understand the following statements or questions. Encircle the
letter that corresponds to the BEST answer.

1. Which of the following types of lipids is generally known as fats that contain a
glycerol attached to three fatty acids?
a) Triglycerides c) Steroids
b) Phospholipids d) Waxes
2. It is the type of fatty acid that is only contain single bonds in the fatty acid chain.
a) Saturated c) Oils
b) Unsaturated d) Fats
3. Which of the following types of fatty acids that is mostly known as oils, contain
one or more double bonds in the fatty acid chain?
a) Saturated c) Oils
b) Unsaturated d) Fats
4. Which of the following is known as a steroid alcohol?
a) Triglycerides c) Cholesterol
b) Phospholipids d) Cortisol
5. Sex hormones are also steroids. Which of the following hormones that can be found
in male?
a) Testosterone c) Estrogen
b) Progesterone d) Cortisol
6. Which of the following types of lipids are combined from certain alcohols and fatty
acid?
a) Triglycerides c) Steroids
b) Phospholipids d) Waxes
7. It is found in leaves and stem that prevents the plant from losing excess water.
a) Triglycerides c) Steroids
b) Phospholipids d) Waxes
8. It is a lipid with a phosphate group.
a) Triglycerides c) Steroids
b) Phospholipids d) Waxes
9. Fats that are commonly found in plants.
a) Saturated c) Oils
b) Unsaturated d) Fats
10. Which of the following does not belongs to the group?
a) Triglycerides c) Steroids
b) Phospholipids d) Cholesterol