chapter 7 section 4

Question 1

What are the main functions of polysaccharides?

Answer 1

Storage, structural support, and recognition.

Question 2

Difference between homopolysaccharides and heteropolysaccharides?

Answer 2

Homopolysaccharides: one type of monosaccharide; Heteropolysaccharides: multiple monosaccharides.

Question 3

Name key storage polysaccharides.

Answer 3

Starch (plants) and glycogen (animals).

Question 4

Name key structural polysaccharides.

Answer 4

Cellulose (plants) and chitin (exoskeletons).

Question 5

What role do cell surface polysaccharides play?

Answer 5

Recognition molecules.

Question 6

What are the two forms of starch

Answer 6

Amylose and amylopectin

Question 7

Describe amylose.

Answer 7

Linear α(1→4) glucose chains, poorly soluble, forms helical micellar suspensions, one reducing end.

Question 8

Describe amylopectin.

Answer 8

Highly branched α(1→4) chains with α(1→6) branches every 12–30 residues.

Question 9

How does iodine test for starch work?

Answer 9

Iodine fits into amylose helices → blue color indicates starch.

Question 10

Why is branching important in amylopectin?

Answer 10

Increases sites for phosphorylase to release glucose-1-P, enabling rapid energy mobilization.

Question 11

What does the starch phosphorylase reaction produce?

Answer 11

α-D-glucose-1-phosphate from amylose, which can be used for energy metabolism.

Question 12

Where is glycogen stored in animals?

Answer 12

Liver (up to 10% mass) and muscle (1–2% mass)

Question 13

How does glycogen differ from amylopectin?

Answer 13

More highly branched: α(1→6) branches every 8–12 residues

Question 14

How does glycogen react with iodine?

Answer 14

Produces a red-violet color.

Question 15

What are dextrans?

Answer 15

Polysaccharides with main α(1→6) glucose linkages; branches can be α(1→2), α(1→3), or α(1→4).

Question 16

How do structural polysaccharides differ from storage polysaccharides?

Answer 16

small differences in linkage types create major changes in properties.

Question 16

What industrial use do cross-linked dextrans have?

Answer 16

Sephadex gels for size-based separation of biomolecules; gels are up to 98% water.

Question 16

What biological role do bacterial dextrans play?

Answer 16

Components of dental plaque, providing protection for oral bacteria.

Question 17

What is cellulose?

Answer 17

A structural polysaccharide found in plant cell walls; most abundant natural polymer.

Question 17

Compare linkages in storage vs structural polysaccharides

Answer 17

Storage (starch, glycogen): mainly α(1→4); Structural (cellulose): β(1→4).

Question 18

Where is cellulose found?

Answer 18

Plant cell walls, wood, bark, and cotton (almost pure cellulose).

Question 19

How do the linkages in cellulose differ from amylose?

Answer 19

Cellulose has β(1→4) linkages → fully extended chains; amylose has α(1→4) → helical.

Question 20

What strengthens cellulose structure?

Answer 20

Hydrogen bonds: intrachain (red) and interchain (green/blue) between sheets.

Question 21

How do ruminant animals digest cellulose?

Answer 21

Bacterial cellulase in the rumen breaks down cellulose into glucose.

Question 22

Who is Ruth Benerito and what did she contribute?

Answer 22

Developed cross-linking of cellulose in cotton → wrinkle-free and permanent press fabrics.

Question 23

What is chitin and where is it found?

Answer 23

Second most abundant structural polysaccharide; found in exoskeletons of arthropods and fungal cell walls.

Question 24

How does chitin differ structurally from cellulose?

Answer 24

C-2 position has an N-acetyl group; strands can be parallel or antiparallel.

Question 25

What are alginates?

Answer 25

Ca²⁺-binding polysaccharides found in algae; used for structural support.

Question 26

What are agarose and agaropectin?

Answer 26

Polysaccharides from red algae; chains of galactose; agarose gels separate biomolecules by size.

Question 27

What is the favored conformation of agarose in solution?

Answer 27

Double helix with a threefold screw axis.

Question 28

What are glycosaminoglycans (GAGs)?

Answer 28

Linear chains of repeating disaccharides containing amino sugars and negative charges; components of proteoglycans.

Question 29

Functions of heparin, hyaluronate, chondroitin, keratan sulfate, and dermatan sulfate?

Answer 29

Heparin – anticoagulant; hyaluronate – synovial fluid and vitreous humor; chondroitin/keratan – connective tissue; dermatan – skin ECM.

Question 30

How are Gram-positive bacterial cell walls structured?

Answer 30

Thick peptidoglycan shell outside cell membrane; tetrapeptides crosslinked via pentaglycine bridges.

Question 31

How are Gram-negative bacterial cell walls structured?

Answer 31

Thin peptidoglycan layer between inner and outer membranes; tetrapeptides crosslinked directly via amide bonds.

Question 32

What is peptidoglycan composed of?

Answer 32

Sugar backbone with tetrapeptides; unusual γ-carboxyl linkage in tetrapeptides.

Question 33

What is the gamma-carboxy linkage of isoglutamate?

Answer 33

A unique bond in tetrapeptide segments of peptidoglycan, contributing to cell wall stability.

Question 34

What is peptidoglycan also called and why?

Answer 34

Murein, from Latin "murus" meaning wall

Question 35

How do Gram-negative bacterial cells appear under a microscope?

Answer 35

“Hairy” due to lipopolysaccharide (LPS) on the outer membrane.

Question 36

What is the structure of Gram-positive bacterial cell walls?

Answer 36

Single bilayer membrane with a thick peptidoglycan coat; reacts with Gram stain.

Question 37

What is the structure of Gram-negative bacterial cell walls?

Answer 37

Two bilayers with peptidoglycan sandwiched in between; outer layer coated with LPS.

Question 38

What is lipopolysaccharide (LPS)?

Answer 38

A molecule coating the outer membrane of Gram-negative bacteria; consists of a lipid anchored in the membrane linked to a long polysaccharide chain.

Question 39

What roles do cell surface polysaccharides play in animals?

Answer 39

Found on glycoproteins and proteoglycans; regulate cell-cell recognition and interaction.

Question 40

What determines the uniqueness of animal cell surface polysaccharides?

Answer 40

the specific enzymes that synthesize the polysaccharides, creating "information" for cell recognition.