Lecture 12: Polysaccharides

Chapter 7.2

True or False: Most carbohydrates in nature occur as polysaccharides without a defined length.

true

What is another term for polysaccharides?

glycans

What are homopolysaccharides?

sugars that contain only a single monomeric sugar species

What are heteropolysaccharides?

sugars that contain 2+ kinds of monomers

What is the function of glycogen?

the energy storage molecule in animals

What is the structure of glycogen?

polymer of (a1 → 4)-linked glucose subunits, with (a1 → 6)-linked branches

What is the function of starch?

an energy storage molecule in plants

What does starch contain?

amylose

What is the structure of starch?

• long, unbranched chains of D-glucose connected by (a1 → 4) linkages (amylose)

• larger than amylose, polymer of (a1 → 4)-linked glucose subunits, with (a1 → 6)-linked branches (amylopectin)

What is the most stable structure for the (a1 → 4)-linked chains of starch and glycogen?

alpha-helical structure with 6 residues per turn

What is cellulose?

a tough, fibrous, water-insoluble substance

What is the most abundant biomaterial on Earth?

cellulose

What is the structure of cellulose?

a linear, unbranched homopolysaccharide, consisting of D-glucose units and is linked by (B1 → 4) glycosidic bonds

True or False: Animals do not have the enzyme to hydrolyze (B1 → 4) glycosidic bonds.

true

What is the function of cellulose?

a functional component of a plant’s cell wall

What is the most stable conformation of cellulose?

a straight, extended chain (each chair is turned 180 degrees relative to its neighbors)

What is the structure of chitin?

a linear homopolysaccharide composed of N-acetylglucosamine residues in (B1 → 4) linkage

True or False: Acetylated amino groups make chitin more hydrophobic and water-resistant than cellulose.

true

Can humans digest chitin?

no, humans are not able to digest chitin

What is the function of peptidoglycan?

a functional component of the bacterial cell wall

What are the characteristics of a gram-positive bacterial cell wall?

• lipoteichoic acid

• peptidoglycan cell wall

• plasma membrane

• alternating copolymer of B(1 → 4)-N-acetyl-D-glucosamine and N-acetylmuramic acid

What are the characteristics of a gram-negative bacterial cell wall?

• outer lipid membrane

• double membrane system

• peptidoglycan

• plasma membrane

What is the structure of peptidoglycan?

a heteropolymer of alternating (B1 → 4)-linked N-acetylglucosamine and N-acetylmuramic acid residues; cross-linked by short peptides

What are glycosaminoglycans?

heteropolysaccharides in the ECM of cells that provide viscosity, adhesiveness, and tensile strength

What is the structure of glycoaminoglycans?

linear polymers composed of repeating disaccharide units

True or False: There’s a concentrated negative charges of molecules on the plasma membrane to attract species such as growth factors and peptides that have a positive charge.

true

What are the types of glycosaminoglycans?

• hyaluronan

• keratan sulfate

• chondroitin 4-sulfate

• heparin

True or False: Glycosaminoglycans usually have on monosaccharide that is always either N-acetylglucosamine or N-acetyl galactosamine and the other is usually a glucuronic acid or iduronic acid. Some contain esterified sulfate groups.

true