Carbohydrate
organic compound made of varying numbers of monosaccharides
Monosaccharide
carbohydrate consisting of a single sugar
Disaccharide
carbohydrate consisting of two monosaccharides bonded together
Simple carbohydrate/simple sugar
category of carbohydrates consisting of mono-and disaccharides
Hexose
monosaccharide made up of 6 carbon atoms
Glucose
a six-carbon monosaccharide produced by photosynthesis in plants
- most abundant sugar in blood
- primary function to provide cells with ATP
Photosynthesis
process whereby plants use energy from the sun to produce glucose from carbon dioxide and water
Fructose
a six-carbon monosaccharide found in fruits and vegetables
- most abundant in fruits and vegetables
Galactose
a six-carbon monosaccharide found mainly bonded with glucose to form the milk sugar lactose
- found in dairy products
Lactose
disaccharide consisting of glucose and galactose; produced by mammary glands
Maltose
disaccharide consisting of two glucose molecules bonded together; formed during the chemical breakdown of starch
Sucrose
disaccharide consisting of glucose and fructose; found primarily in fruits and vegetables
Glycosidic bond
a type of chemical bond that forms between two monosaccharides
- formed by a condensation reaction, release of a water molecule
Alpha (A) glycosidic bond
a downward facing type of glyco-bond between two monosaccharides
Beta (B) glycosidic bond
an upward facing type of glyco-bond between two monosaccharides
Complex carbohydrates
category of carbohydrate that includes oligosaccharides and polysaccharides
Oligosaccharide
carbohydrate made of relatively few (3-10) monosaccharides
- present in a variety of foods: beans, peas, lentils
- raffinose and stachyose
- undigestable in the large intestine
- components of cell membranes, allowing cells to recognize and interact with
Polysaccharide
complex carbohydrate made of many monosaccharides (10+)
- types: starch, glycogen, dietary fiber
Amylose
a type of starch consisting of a linear chain of glucose molecules
- a1,4 bonds
Amylopectin
a type of starch consisting of a highly branched arrangement of glucose molecules
- a1,4 & a1,6 bonds
Glycogen
polysaccharide consisting of a highly branches arrangement of glucose molecules; found primarily in liver and skeletal muscles
- can be broken down quickly when energy is needed
- body turns to _____ when glucose availability is low
Carbohydrate loading
a technique used to increase the body's glycogen stores
Fiber
polysaccharide found in plants that is not digested or absorbed in the human small intestine
Dietary fiber
fiber that naturally occurs in plants
Functional fiber
fiber that is added to food to provide beneficial physiological effects
- added to food as an ingredient
Total fiber
the combination of dietary fiber and functional fiber
Soluble fiber
dietary fiber that dissolves in water
Insoluble fiber
dietary fiber that does not dissolve in water
Bran
the outer layer of a grain; contains most of the fiber
Germ fiber
portion of a grain that contains most of its vitamins and minerals
Endosperm
the portion of a grain that contains mostly starch
Whole-grain foods
cereal grains that contain bran, endosperm, and germ in the same relative proportions as they exist naturally
Salivary alpha-amylase
enzyme produced by salivary glands, digesting starch by hydrolyzing alpha 1,4 glyco-bonds
Dextrin
partial breakdown product formed by starch digestion, consisting of glucose units
Pancreatic alpha-amylase
enzyme, produced by the pancreas, digests starch by hydrolyzing a1,4 glyco-bonds
Maltase
brush border enzyme that hydrolyzes maltose into two glucose molecules
Brush border enzyme
enzyme, produced by enterocytes, aiding in the final steps of digestion
Limit dextrin
partial breakdown product formed during amylopectin digestion that contains 3-4 glucose molecules an an a1,6 glyco-bond
Alpha-dextrinase
brush border enzyme that hydrolyzes a1,6 glyco-bonds
Disaccharidase
brush border enzyme that hydrolyzes glyco-bonds in disaccharides
Sucrase
brush border enzyme that hydrolyzes sucrose into glucose and fructorse
Lactase
brush border enzyme that hydrolyzes lactose into glucose and galactose
Lactose intolerance
inability to digest the milk sugar lactose, caused by a lack of enzyme lactase
Carbohydrate digestion
Goal of ______ is to break down large, complex molecules such as starch into small, absorbable monosaccharides, requiring a series of enzymes
Steps of starch digestion
1. digestion of amylose and amylopectin in the mouth
2. there is no digestion of amylose and amylopectin in the stomach
3. digestion of amylose and amylopectin in the small intestine
4. digestion of amylose and amylopectin on the brush border of the small
Step #1: mouth digestion
- amylose: salivary glands release amylase, hydrolyzing a1,4, glycosidic bonds in amylose, forming dextrin
- amylopectin: salivary glands release salivary alpha-amylase, hydrolyzing a1,4 glycosidic bonds in amylopectin, forming dextrins
Step #2: stomach digestion
- amylose/amylopectin: acidity of gastric juice destroys the enzymatic activity of salivary alpha-amylase. dextrins pass unchanged in the small intestine.
Step #3: small intestine digestion
- amylose: pancreas releases pancreatic alpha-amylase into the small intestine, p.alpha-amylse hydrolyzes a1,4 glycosidic bonds in amylose. dextrin are broken down into maltose.
- amylopectin: pancreas releases pancreatic alpha-amylase into the small inte
Step #4: brush border digestion
- amylose: maltose is hydrolyzed by maltase (brush border enzyme), forming free glucose
- amylopectin: maltose is hydrolyzed by maltase, forming free glucose. a1,6 glycosidic bonds in limit dextrin are hydrolyzed by alpha-dextrinase, brush border enzyme,