carbohydrates I

what is the most abundant food source?

carbohydrates

what percentage of carbohydrates contribute to energy for humans?

50

what do all carbohydrates contain?

carbon, oxygen, and hydrogen

what are the two classifications of carbs?

simple sugars and complex carbohydrates

what are the simple sugars?

monosaccharides and disaccharides

what are the complex carbohydrates?

oligosaccharides and polysaccharides

how many chains of molecules do oligosaccharides have?

3-12

how many chains of molecules do polysaccharides have?

more than 12

can monosaccharides be broken down into smaller molecules?

no

what are the most common monosaccharides?

glucose, fructose, and galactose

what is ribose a part of?

ATP

what are the two classifications of monosaccharides?

ketone or ketose and aldehyde or aldose

what is the most reactive monosaccharides?

aldehyde or aldose

what is an isomer?

• when there are identical molecular formulas but with different structures

• mirror images of each other - have hydroxyl groups on opposite sides

what are stereoisomers?

• 2 or more molecules have the same molecular composition, but the bonds differ in their 3 dimensional orientation

• D-glucose or L-glucose

what is the importance of isomers?

different isomers often have distinct roles in biological processes

what is the difference between D-glucose and L-glucose?

D-glucose is biologically active, while L-glucose is rare emtabolized

what are reducing sugars?

a type of carbohydrate that can act as reducing agents because they have a free aldehyde group (-CHO) or a free ketone group (-C=O)

are reducing sugars capable of donating electrons?

yes

what are examples of sugars that reduce other substances during reactions?

glucose, galactose, fructose, ribose, xylose, and glyceraldehyde

what is important in energy reactions?

• production of ATP for energy

• ability to reduce compounds is also used in clinical settings to test for sugars in urine, which cn indicate diabetes mellitus

what is the role of non-reducing suagrs?

• do not directly produce energy

• have other roles in the body

• converted to substances that produce energy

what is a disaccharide?

• 2 monosaccharides units linked together with a glycosidic bond

• one hydroxyl group linked to another hydroxyl group

what are examples of disaccharides?

maltose, lactose, and sucrose

what is maltose made of?

2 glucose molecules

how does matolse occur?

it results from the breakdown of starch

is maltose a reducing sugar?

yes, carbon of the glucose unit can react with another molecule

what are popular sources of maltose?

beer and malt liquors

what is lactose made of?

one glucose and 1 galactose

is lactose a reducing sugar?

yes

what are popular sources of lactose?

milk and milk products

what is sucrose made of?

one glucose and one fructose molecule

what are popular sources of sucrose?

baked goods, candy, and other processed foods, fruits, and vegetables

what is trehalose?

• its unique in its structure

• when consumed it is digested more slowly

• has a low glycemic response

• tastes about half as sweet as foods

• non-reducing sugar

what are popular sources of trehalose?

• yeast

• mushrooms

• shrimp

• other plants

what is trehalose used for?

an additive in processed foods as a stabilized

what are artificial sweeteners?

sucralose

what is sucralose made of?

sugar and 3 hydroxyl groups are replaced by a chloride molecule

can artificial sweeteners be digested?

no

do artificial sweeteners raise blood sugar levels?

no

what is another name for artificial sweeteners?

splenda

where can you find splenda?

• diet drinks

• protein powders and meal replacements

• sweetened condiments

• dairy products

• chewing gum and candy

what are common oligosaccharides?

raffinose, stachyose, and verbascose

what makes up an oligosaccharide?

3-10 molecules of glucose, galactose, and fructose molecules in chain

can human digestive enzymes digest glycosidic bonds?

no

what can digest glycosidic bonds?

bacteria in the colon

do oligosaccharides have alpha or beta linkages?

beta

what are popular food sources of oligosaccharides?

• beans

• peas

• lentils

• bran

• whole grains

what happens if you consume large amounts of oligosaccharides?

• intestinal discomfort and gas

• serves as a probiotic

where are human milk oligosaccharides found?

breast milk

what is fructo-oligosaccharides (FOS)?

• similar to raffinose and cannot be digested and acts as a prebiotic

• chains of primarily fructose molecules

what are popular sources of fructo-oligosaccharides?

• onions

• asparagus

• wheat

• tomatoes

• grains

what does FODMAPS stand for?

fermentable, oligosaccharides, disaccharides, monosaccharides, and polyols

what are oligosaccharides that don’t naturally occur in food called?

dextrins

what are dextrins?

• made from starch that has been hydrolyzed (partially broken down)

• made entirely of glucose

• not naturally found in foods - used more as a additive

• dextrins that are 3-20 units long are used in food and drug productions

• are easily digested except for wheat dextrins

what is the function of dextrins?

• thickening agents

• crystalizing agents

• fat replacers

• crisping agents

• energy source in shakes and tube feedings

what are polysaccharides?

starch, glucose, and cellulose

what are homopolysaccharides?

all the molecules in the chain are the same sugar

what are heteropolysaccharides?

several different sugar molecules make up the chain

which polysaccharide is more abundant and has more of a nutritional impact?

homopolysaccharides

what is starch?

digestible polysaccharide in plants

what are the two types of starch from plants?

amylose and amylopectin

what is amylose?

• linear chain

• 15-20% of starch in plants

what is amylopectin?

• branched chain

• 80-85% of the starch in plants

what is glycogen?

• structure is similar to amylopectin

• major form of carbohydrates in animal tissues

can glycogen be broken down into glucose and then enter metabolic pathways when the body needs more energy?

yes

does meat or animal flesh contain glycogen when we eat it?

no

what is cellulose?

• major component of cell walls in plants

• indigestible carbohydrate

• linked together by beta glycosidic bonds which alpha amylase enzymes cant break down

is cellulose considered a primary energy source?

no, because it is indigestible and classified as a fiber

why do we need to know about carbohydrate structures?

• determines how they are digested and absorbed

• what enzymes are available to break down and the rate of breakdown

• how they provide energy and through which pathways