Breaking Down Carbohydrate
Carbohydrates are categorized as either simple or complex. The simple carbohydrates are made of a single unit of various arrangements of the three elements (carbon, hydrogen, oxygen). Each unit has the same number of carbon, hydrogen, and oxygen atoms; the different arrangements of them account for their distinct properties, such as sweetness and solubility. Complex carbohydrates are made of different arrangements of these single units that are linked together in various patterns that can be from two to tens of thousands of units long. The more units linked, the more complex the carbohydrate. Simple carbohydrates are sugars; complex carbohydrates are starches, fiber, glycogen, and dextrin.
Simple Carbohydrates
the food, such as the lactose in milk and fructose in fruits, as well
as sugar that's been added to the food, such as table sugar, corn
syrup, and dextrose.
There
are two kinds of simple carbohydrates: monosaccharides and
disaccharides. Each type is quite easily broken down by the body to
create the glucose the body uses for energy.
Monosaccharides. These
are the simplest form of carbohydrate ("mono" means one, "saccharide"
means sugar). Glucose, fructose, and galactose, the monosaccharides that
are found in fruits, vegetables, and milk, make up approximately 10
percent of the carbohydrate in our diet. Glucose is often called blood
sugar because it is the main form of carbohydrate that travels through
the bloodstream to provide energy to the body's cells. It's found
naturally in fruits, vegetables, and honey. Fructose, also known as
fruit sugar, is found naturally in many different fruits as well as
honey. Galactose is a monosaccharide that is the end result of the
digestive breakdown of a disaccharide called lactose (the sugar found in
milk).
Disaccharides.
These are made of two single sugar units (monosaccharides) that are
linked together. The different types of disaccharides ("di" means two)
are created through various combinations of monosaccharides. Here are
some examples of disaccharides you might recognize and how they are
formed:
glucose + fructose = sucrose (disaccharide)
glucose + galactose = lactose (disaccharide)
glucose + glucose = maltose (disaccharide)
Sucrose
is the most common disaccharide; it's commonly known as table sugar.
Lactose is the disaccharide found in milk. Maltose is the least common
disaccharide; it's created during digestion by enzymes that break down
large molecules of starch and is a product of cereal grain germination.
Complex Carbohydrates
Complex
carbohydrates are assembled from single sugar units, including glucose,
fructose, and galactose, or pairs of single sugars (the disaccharides,
including sucrose, lactose, and maltose) that are linked together.
Here's how complex carbs are formed:
Polysaccharides. Polysaccharides
("poly" means more than one) are also known as complex carbohydrates
and include starch, fiber, glycogen, and dextrin. Although complex
carbohydrates are built from many single sugar units, they don't taste
sweet. Joining these sugar units together creates the new, complex
carbohydrate-either starch, glycogen, or cellulose (fiber). Starch is
found in plants (starch is their storage form of carbohydrate), glycogen
is the storage form of carbohydrate in humans and animals, and
cellulose, an indigestible form of carbohydrate that's better known as
fiber, provides structure for all plants. A fourth type of
polysaccharide, dextrin, is produced as a result of breaking down long
chains of starch into shorter chains during digestion. All of these
complex carbohydrates are more stable and less soluble than the simple
carbohydrates. However, the body can still break them down fairly easily
into simple sugars and finally into glucose, the simple sugar that the
body uses directly for energy.
The chemical composition of
carbohydrates is a nice starting point, but the real information you
probably want to know about carbs is how they are used by the body. In
the next section, we'll examine what happens when we eat simple and
complex carbohydrates.
