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One of the common features of organisms here on
Earth is their biochemical composition. All organisms
contain a common set of chemicals, such as carbon (C),
oxygen (0), nitrogen (N), phosphorus (P), sulfur (S), and
hydrogen (H), which build larger and more complex
molecules necessary in life. These large molecules-
carbohydrates, lipids, proteins, and nucleic acids combine
to produce different structures or substances that perform
specific functions in the cell. These are called the
biomolecules. Also known as organic molecules or
macromolecules (due to their large size and complex
nature), biomolecules serve as fuel for the metabolism of
organisms. Their chemical composition and quantity are
important for cellular activities to proceed.
Cellular activities in your body may not function
properly if you are deficient of certain
biomolecules. What you are consuming may not have the
right type and amount of biomolecules necessary for these
processes, and this may make you an unhealthy person.
These biomolecules may already be familiar to you, as they
are always present in certain nutrition labels of food
products. Knowledge of these biomolecules is necessary in
nutrition awareness. Biomolecules occur naturally in
organisms. As mentioned, there are four major types of
biomolecules: carbohydrates, proteins, lipids, and nucleic
acids. Let’s study each one in more detail.
CARBOHYDRATES
Carbohydrates are biomolecules believed to be the
most abundant of all organic compounds. This is based on
the assumption that cellulose, a type of carbohydrate, is
produced by numerous photosynthetic organisms daily
through photosynthesis. It is said that more than 75% of
the dry weight of plants is carbohydrate in nature
(Khowala, 2008).
Majority of carbohydrates have a carbon-hydrogen-
oxygen ratio of 1:2:1. The term carbohydrate literally
means “hydrated carbon.” Carbohydrates include simple
and complex sugars. Carbohydrates are well-known as
great sources of energy. When our bodies are powered by
energy, our brains function well and our muscles can work
properly.
Aside from their energy giving properties, carbohydrates
have other important roles and functions in the body.
BIG IDEA!
Carbohydrates are great sources of energy. For
bodily functions to perform well and for
You to be alert the whole day. Carbohydrates are best
taken in the beginning of the day, but they have to be
consumed at a lesser amount at night, when your body
needs to rest.
Types and Functions of Carbohydrates
MONOSACCHARIDES - are also called simple sugars
because they are the monomers, or the single structural
units, of some complex carbohydrates that will be
discussed later. They can be classified as aldoses or ketoses
according to the placement of chemicals in the structure.
Aldoses are characterized by the presence of an aldehyde (-
CHO), usually at the terminal, or the first carbon atom.
Ketoses, on the other hand, are characterized by having a
carbonyl (C=O) group, or a ketone, which is usually located
at the second carbon atom of the molecule. When the
carbonyl group is mixed with the hydroxyl group (-OH) in an
aqueous solution, the result is a cyclic compound (either
hemi-acetal or hemi-ketal), which looks like a water-soluble
crystalline solid.
Fig. 7.1. Here are the structural formulas of fructose and glucose.
Fructose and glucose are examples of hexoses with six carbon atoms.
Glucose is an aldose, with an aldehyde located at its terminal ‘carbon
atom. Fructose is a ketose, with a ketone functional group at the second
carbon atom.
A monosaccharide can also be classified according
to the number of carbon atoms it has. Thus,
monosaccharides with two carbon atoms are considered as
dioses, those with three carbon atoms are trioses, and so
on. One familiar example is the pentose (an organic
compound composed of five carbon atoms), which includes
the ribose found in ribonucleic acid (RNA) and some
vitamins. RNA is one of those responsible for encoding the
genetic information found in DNA. Glucose, a hexose (an
organic compound composed of six carbon atoms), is
another important example of a monosaccharide, as it is a
major source of energy for all organisms. Another example
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