MN07 - Complex Carbs and Dietary Carbs

What are the main functions of carbohydrates in the body?

Carbohydrates serve as an energy source (4 kcal/g), are stored as glycogen and fats, function as structural components of cell walls and DNA, participate in cell-cell signaling, and are involved in binding between molecules.

What is the general chemical formula for carbohydrates?

The general formula for carbohydrates is (CH2O)n.

What defines an aldose carbohydrate?

An aldose contains an aldehyde functional group (example: glucose).

What defines a ketose carbohydrate?

A ketose contains a ketone functional group (example: fructose).

What is a monosaccharide?

A monosaccharide is a single sugar unit.

What is a disaccharide?

A disaccharide consists of two sugar molecules joined by an O-glycosidic bond.

What is a polysaccharide?

A polysaccharide consists of more than 10 monosaccharide units linked together.

What is a glycosidic bond in carbohydrates?

A glycosidic bond is a covalent bond between the -OH group of the anomeric carbon of a carbohydrate and the -OH or -NH group of another molecule.

What is an O-glycosidic bond?

An O-glycosidic bond is formed between the carbohydrate and an -OH group (such as on serine, threonine, or another carbohydrate).

What is an N-glycosidic bond?

An N-glycosidic bond is formed between the carbohydrate and an -NH group (such as on asparagine).

Which enzyme catalyzes the formation of glycosidic bonds?

Glycosyltransferases catalyze the formation of glycosidic bonds.

What monosaccharides make up sucrose and where is it found?

Sucrose is composed of glucose and fructose and is found in table sugar (cane or beet), maple sugar, fruits, and vegetables.

What monosaccharides make up lactose and where is it found?

Lactose is composed of glucose and galactose and is found in milk and milk products.

What monosaccharides make up maltose and where is it found?

Maltose is composed of glucose and glucose and is found as a product of starch hydrolysis and in germinating cereals and beer.

What is a homopolysaccharide?

A homopolysaccharide is a polysaccharide composed of only one type of monomer.

What is a heteropolysaccharide?

A heteropolysaccharide is a polysaccharide composed of multiple types of monomers.

What type of polysaccharide is glycogen?

Glycogen is a branched homopolysaccharide of glucose.

What bonds form the chains in glycogen?

α1→4 glycosidic bonds form the chains.

What bonds form the branch points in glycogen?

α1→6 glycosidic bonds form branch points every 8-12 residues.

What is the function and location of glycogen?

Glycogen is the primary storage polysaccharide in animals and is stored in the liver and muscles.

What are the two components of starch?

Amylose and amylopectin.

What is the structure of amylose?

Amylose is an unbranched polymer of glucose with α1→4 linkages.

What is the structure of amylopectin?

Amylopectin is a branched polymer with α1→6 linkages every 24-30 residues.

What is the function and source of starch?

Starch is the main storage polysaccharide in plants and is found in grains, legumes, and tubers.

What is the structure of cellulose?

Cellulose is a linear homopolysaccharide of glucose with β1→4 linkages.

What is the function of cellulose?

Cellulose is the main structural carbohydrate in plants.

Why is cellulose indigestible in humans?

Cellulose is indigestible because humans cannot break β1→4 glycosidic bonds.

What are the three major classes of complex carbohydrates?

Proteoglycans, glycoproteins, and glycolipids.

What are proteoglycans composed of and what is their function?

Proteoglycans consist of long chains of glycosaminoglycans attached to a core protein, are ~95% carbohydrate by weight, and function in structural support and lubrication in the extracellular matrix.

What defines glycoproteins structurally and functionally?

Glycoproteins are proteins with small, branched oligosaccharides attached, with protein as the major component, and function as membrane proteins and blood group antigens.

What are glycolipids?

Glycolipids are sphingolipids that contain complex carbohydrates.

What are glycosaminoglycans?

GAGs are long, linear, negatively charged heteropolysaccharides composed of repeating disaccharide units.

What are the key features of hyaluronic acid?

It is not sulfated, is the largest GAG, binds large amounts of water, functions as a lubricant and shock absorber, and is found in synovial fluid and vitreous humor.

What are the key features of heparin?

Heparin is an anticoagulant found in mast cell granules and is released during inflammatory and allergic reactions.

What are the key features of heparan sulfate?

It is found in basement membranes, has a strong negative charge, and is the only GAG present in the CNS.

What are the key features of chondroitin sulfate?

It is the most abundant GAG, is a major component of cartilage, and is lost in osteoarthritis due to proteoglycan degradation.

What are the key features of keratan sulfate?

It is found in the cornea, bone, and cartilage and is associated with chondroitin sulfate.

What are the key features of dermatan sulfate?

It is found in skin, blood vessels, and heart valves and is increased in mitral valve prolapse.

What happens when disaccharide digestion is impaired?

Undigested carbohydrates pass into the large intestine, increasing osmolarity and causing osmotic diarrhea.

What gases are produced from bacterial fermentation of undigested carbohydrates?

Carbon dioxide (CO2) and hydrogen (H2).

What symptoms result from carbohydrate fermentation in the intestine?

Flatulence and cramps.

What is lactase nonpersistence?

Lactase nonpersistence (hypolactasia) is a condition where lactase activity declines, leading to lactose intolerance.

What percentage of adults are lactase deficient?

Approximately 60%.

When does lactase activity begin to decline?

Around age 2.

What determines blood group antigens on red blood cells?

The specificity of glycosyltransferases.

What is the H antigen?

A base antigen consisting of fucose attached to a glycolipid, present in all blood types.

What defines blood type O?

No active glycosyltransferase, so no additional sugar is added to the H antigen.

What defines blood type A?

Addition of N-acetylgalactosamine (GalNAc) to the H antigen.

What defines blood type B?

Addition of galactose (Gal) to the H antigen.

What defines blood type AB?

Presence of both A and B antigens.

What is the glycemic index?

A ranking system based on the degree and duration of blood glucose elevation after a meal.

What is the glycemic index range?

0 to 100, with pure glucose at 100.

What does a low glycemic index indicate?

A slower increase in blood glucose after eating.

What types of foods have a high glycemic index?

Highly processed foods.

What types of foods have a low glycemic index?

Foods high in fiber or fat.

What factors affect glycemic index?

Processing, physical form, ripeness, and combination with fats and acids.

What is glycemic load?

A measure of blood glucose impact that considers both the glycemic index and the amount of carbohydrate consumed.

What is the formula for glycemic load?

GL = (GI × grams of carbohydrate) / 100.

What are the sources of dietary fiber?

Fruits, vegetables, legumes, and whole grains.

What is functional fiber?

Fiber that is added to foods as a supplement.

What is total fiber?

The sum of dietary fiber and functional fiber.

How does fiber relate to glycemic index and satiety?

High-fiber foods tend to have a lower glycemic index, increase satiety, and help limit caloric intake.

What are nutritive sweeteners?

Sweeteners that provide calories and energy.

What are examples of natural nutritive sweeteners?

Honey, maple syrup, and agave nectar.

What are examples of refined nutritive sweeteners?

Table sugar and high-fructose corn syrup.

What are non-nutritive sweeteners?

Sweeteners that provide little or no calories and are much sweeter than sugar.

What are examples of natural non-nutritive sweeteners?

Stevia, monk fruit, and thaumatin.

What are artificial sweeteners?

Man-made non-nutritive sweeteners such as aspartame, saccharin, sucralose, acesulfame-K, advantame, and neotame.