Chapter 4- The Carbohydrates: Sugars, Starches, and Fibers Flashcards
Carbohydrates are made of
carbon, hydrogen and oxygen atoms.
Structure
R-OH
Monosaccharrides are single sugars (most are hexoses).
Glucose
Fructose
Galactose
Glucose
serves as the essential energy source, and is commonly known as blood sugar or dextrose.
Fructose
is the sweetest, occurs naturally in honey and fruits, and is added to many foods in the form of high-fructose corn syrup.
5C
Galactose
rarely occurs naturally as a single sugar.
Disaccharides
are pairs of monosaccharides, one of which is always glucose
Condensation reactions
link monosaccharides together.
Release H2O
Hydrolysis reactions
split molecules and commonly occur during digestion.
Use
H2O
Maltose
consists of two glucose units. It is produced during the germination of seeds and fermentation.
Sucrose
is fructose and glucose combined. It is refined from sugarcane and sugar beets, tastes sweet, and is readily available.
Lactose
is galactose and glucose combined. It is found in milk and milk products.
oligosaccharides
3-9 glucose chain
polysaccharides
Many glucose units
Chains
Straight or branched
Glycogen
Storage form of glucose in the body
Provides a rapid release of energy when needed
Starches
Storage form of glucose in plants
Found in grains, tubers, and legumes
Dietary fibers
provide structure in plants, are very diverse, and cannot be broken down by human enzymes.
Soluble and insoluble
Soluble Fibres
are viscous and can be digested by intestinal bacteria (this property is also known as fermentability). These fibers are found in fruits and vegetables.
Reduce cholesterol, binds to bile salts
Insoluble Fibre
are nonviscous and are not digested by intestinal bacteria. These fibers are found in grains and vegetables.
In the mouth,
the salivary enzyme amylase begins to hydrolyze starch into short polysaccharides and maltose.
In the stomach,
acid continues to hydrolyze starch while fiber delays gastric emptying and provides a feeling of fullness (satiety).
In the small intestine,
pancreatic amylase among other enzymes (maltase, sucrase, and lactase) hydrolyzes starches to disaccharides and monosaccharides.
In the large intestine
fibers remain and attract water, soften stools and ferment.
Carbohydrate Absorption
Primarily takes place in the small intestine
The body stores glucose
as glycogen in liver and muscle cells.
if glycogen stores are available
The body uses glucose for energy
If glycogen stores are depleted
the body makes glucose from protein
