MODULE 9: Chapter 9.2

Question 1

What is glycolysis?

Answer 1

The splitting of one molecule of glucose into two molecules of pyruvate.

Question 2

What is the molecular formula of glucose?

Answer 2

C6H12O6

Question 3

What type of sugar is glucose?

Answer 3

A polyhydroxyaldehyde.

Question 4

What type of sugar is fructose?

Answer 4

A polyhydroxyketone.

Question 5

What are the two forms of monosaccharides represented in Figure 9.5?

Answer 5

Fischer projections and Haworth perspectives.

Question 6

What structural forms do monosaccharides exist in?

Answer 6

An equilibrium between linear and cyclic forms.

Question 7

What conformations can glucose be represented by?

Answer 7

Chair or boat conformations.

Question 8

What is the primary source of glucose for non-photosynthetic organisms?

Answer 8

Their environment.

Question 9

What is the primary source of glucose for photosynthetic organisms?

Answer 9

Carbon fixation.

Question 10

What is the sensation of sweetness attributed to?

Answer 10

Ligand activation of G protein–coupled receptor signaling in taste cells.

Question 11

How much sweeter is fructose compared to glucose?

Answer 11

2.3 times sweeter.

Question 12

What is sucralose and how sweet is it compared to sucrose?

Answer 12

A chlorinated sucrose molecule that is 600 times sweeter than sucrose.

Question 13

What is aspartame?

Answer 13

A dipeptide derivative of aspartate and phenylalanine.

Question 14

What distinguishes aldose sugars from ketose sugars?

Answer 14

Aldoses have the carbonyl carbon at the end of the carbon chain, while ketoses have it in the second position.

Question 15

What is the smallest monosaccharide?

Answer 15

Glyceraldehyde.

Question 16

What is a chiral center?

Answer 16

A carbon atom bonded to four different chemical groups.

Question 17

What are enantiomers?

Answer 17

Mirror-image isomers that exist in nature.

Question 18

What defines the D and L isomers of monosaccharides?

Answer 18

The position of the hydroxyl group in the Fischer projection.

Question 19

What are epimers?

Answer 19

Monosaccharides that differ in the position of the hydroxyl group around one carbon atom.

Question 20

What is the ratio of α-D-glucose to β-D-glucose in aqueous solution?

Answer 20

About 40:60.

Question 21

What is the anomeric carbon?

Answer 21

The C-1 carbon of cyclic D-glucose.

Question 22

What are the cyclic forms of glucose called?

Answer 22

α-D-glucopyranose and β-D-glucopyranose.

Question 23

What are furanoses?

Answer 23

Cyclic structures of ketoses like fructose that contain five carbons.

Question 24

What is the normal concentration of glucose in human blood?

Answer 24

~3.5 to 5.5 mM (60–100 mg/dL).

Question 25

What are reducing sugars?

Answer 25

Sugars that can reduce Cu2+, such as glucose, galactose, and lactose.

Question 26

What is Benedict's test used for?

Answer 26

To measure the amount of glucose in a solution based on Cu2+ reduction.

Question 27

What is a more accurate method for measuring blood glucose levels than Benedict's test?

Answer 27

The glucose oxidase–peroxidase enzymatic reaction.

Question 28

What happens to the color of solutions in Benedict's test when reducing sugars are present?

Answer 28

The color changes from blue to red.

Question 29

What is the implication of glucose concentrations above 7.2 mM in blood?

Answer 29

It is considered a diagnostic indicator of diabetes.

Question 30

Fill in the blank: Monosaccharides can be categorized by the number of carbons, such as ______ for three carbons.

Answer 30

triose

Question 31

Fill in the blank: When the carbonyl carbon is in the second position, the sugar is classified as a ______.

Answer 31

ketose

Question 32

What is the qualitative color change of Cu2⁺ reduction by glucose?

Answer 32

Not very accurate and not sensitive enough to detect small changes in blood or urine glucose levels.

Question 33

Which other reducing sugars can reduce Cu2⁺ besides glucose?

Answer 33

Galactose and lactose.

Question 34

How can ketose sugars such as fructose be oxidized?

Answer 34

By conversion of the ketone in alkaline Benedict’s solution to an aldehyde through an enediol intermediate.

Question 35

What enzyme is used in the improved blood glucose test?

Answer 35

Glucose oxidase.

Question 36

What are the products of the reaction catalyzed by glucose oxidase?

Answer 36

Gluconate and hydrogen peroxide (H2O2).

Question 37

What role does peroxidase play in the blood glucose test?

Answer 37

Catalyzes a redox reaction that changes a colorless reduced dye into a colored oxidized product.

Question 38

What is the significance of the home-based glucose-monitoring device?

Answer 38

It allows diabetic patients to conveniently monitor their blood glucose levels.

Question 39

What are disaccharides formed from?

Answer 39

A condensation reaction between two monosaccharides.

Question 40

What type of bond connects monosaccharides in disaccharides?

Answer 40

O-glycosidic bond.

Question 41

How is maltose represented in shorthand nomenclature?

Answer 41

Glc(α1→4)Glc.

Question 42

What is the structure of lactose?

Answer 42

Gal(β1→4)Glc.

Question 43

What is the structure of sucrose?

Answer 43

Glc(α1↔β2)Fru.

Question 44

What is trehalose made of?

Answer 44

Glc(α1↔α1)Glc.

Question 45

Why is lactose considered a reducing sugar?

Answer 45

It contains an anomeric carbon that can form an aldehyde group in the open-chain conformation.

Question 46

What distinguishes nonreducing sugars like sucrose and trehalose?

Answer 46

Both C-1 anomeric carbons are covalently linked by the glycosidic bond.

Question 47

What is the role of amylase in relation to maltose?

Answer 47

It hydrolyzes starch to release the two glucose units.

Question 48

What is the biochemical explanation for aspartame's sweetness compared to galactose?

Answer 48

Higher binding affinity and/or slower off-rate for gustatory receptors.

Question 49

What is the millimolar equivalent of 200 mg/dL serum glucose?

Answer 49

Approximately 11.1 mM.

Question 50

What is an aldose?

Answer 50

A monosaccharide that contains an aldehyde functional group.

Question 51

What is a ketose?

Answer 51

A monosaccharide that contains a ketone functional group.

Question 52

What is a chiral center?

Answer 52

The atom within a molecule that makes that molecule chiral.

Question 53

What is an epimer?

Answer 53

One of a pair of monosaccharides that differ only in the position of a hydroxyl group around a single carbon atom.

Question 54

What is a hemiacetal?

Answer 54

A molecule formed by the reaction of an alcohol and an aldehyde-containing compound.

Question 55

What is a hemiketal?

Answer 55

A molecule formed by the reaction of an alcohol and a ketone-containing compound.

Question 56

What is an anomeric carbon?

Answer 56

The carbon molecule in a cyclic monosaccharide derived from the carbonyl carbon of the linear form.

Question 57

What is an anomer?

Answer 57

One of two stereoisomers that differ in configuration at the anomeric carbon.

Question 58

What are pyranose and furanose?

Answer 58

Pyranose: cyclic hexose sugars; Furanose: cyclic sugar formed from a ketohexose or an aldopentose.

Question 59

What is Benedict’s test used for?

Answer 59

Detecting the presence of reducing sugars in solution.

Question 60

What is a reducing sugar?

Answer 60

A carbohydrate that reduces an oxidizing agent, such as cupric ion (Cu2⁺).

Question 61

What is a nonreducing sugar?

Answer 61

A carbohydrate that is unable to reduce an oxidizing agent.

Question 62

Fill in the blank: The covalent bond that links two monosaccharides together through oxygen is called an _______.

Answer 62

O-glycosidic bond.