Chapter 8

Question 1

What is the empirical formula for any carbohydrate? Specify what n must be greater than or equal to.

Answer 1

(CH2O)n, where n is greater than or equal to 3

Question 2

How do we name carbohydrates?

Answer 2

By the number of units they contain.

Question 3

What differentiates an oligosaccharide from a polysaccharide?

Answer 3

An oligo saccharide has 2-20 units, and a polysaccharide has more than 20 monosaccharides

Question 4

Define “glycoconjugate”

Answer 4

A modified carbohydrate

Question 5

D-Glucose and D-Fructose are two common monosaccharides. What differentiates them from each other? Include information pertaining to aldehydes and ketones within their structures, and how we refer to them.

Answer 5

In glucose, carbon 1 is oxidized to an aldehyde. Referred to as an aldose.
In fructose, carbon 2 is oxidized to a ketone. Referred to as a ketose.

Question 6

(T/F) The aldehyde and ketone groups within carbohydrates cannot react with groups further down the carbohydrate structure.

Answer 6

False. Aldehydes and ketones can react with an alcohol group, forming either a hemiacetal or a hemiketal.

Question 7

When aldehydes or ketones react with alcohols further down the carbohydrate structure, what happens to the overall structure of the carbohydrate?

Answer 7

A closing of the linear chain to form a cyclic structure occurs.

Question 8

When the aldehyde group within glucose reacts with an alcohol within the carbohydrate structure, what kind of ring is formed? How do we refer to cyclic glucose?

Answer 8

A 6-membered ring is formed. It resembles a pyran ring, so we refer to cyclic glucose as alpha-D-glucopyranose

Question 9

When the ketone group within fructose reacts with an alcohol within the carbohydrate structure, what kind of ring is formed? How do we refer to cyclic fructose?

Answer 9

A 5-membered ring is formed. It resembles a furan ring, so we refer to cyclic fructose as alpha-D-fructofuranose

Question 10

Most monosaccharides that are at least 4 carbons or longer will predominantly be in the (linear, cyclic) form.

Answer 10

Cyclic

Question 11

Define what an anomeric carbon is.

Answer 11

Anomeric carbon: The most oxidized carbon of a cyclized monosaccharide

Question 12

What differentiates the alpha from the beta configuration of the anomeric carbon in ring structures? Which can be said to resemble a trans conformation? Cis?

Answer 12

In the alpha configuration, the alcohol group on the anomeric carbon is on the opposite side of the ring from the CH2OH group on carbon 5 (sort of like trans conformation).
In the beta configuration, the alcohol group on the anomeric carbon is on the same side of the ring from the CH2OH group on carbon 5 (sort of like cis conformation).

Question 13

In hexoses, what is special about carbon 5?

Answer 13

In hexoses, carbon 5 is a chiral carbon that is used to designate the sugar as D or L stereoisomer. Most sugars used for energy production in the body will be in the D form.

Question 14

What is a glycosidic bond?

Answer 14

A primary structural linkage involving monosaccharide subunits hooked together into polysaccharides

Question 15

What kind of linkages are glycosidic bonds?

Answer 15

Acetal linkages. The sugar anomeric carbon is condensed with an alcohol. Can also form with an amine or thiol group in modified sugars

Question 16

Compounds containing glycosidic bonds are sometimes called ______.

Answer 16

Glycosides

Question 17

Name 2 compounds that are joined together with glycosidic linkages.

Answer 17

Lactose, sucrose.

Question 18

Describe the structure of lactose, indicating which monomers it is made up of and what kind of specific bond (alpha or beta) joins those monomers.

Answer 18

Lactose consists of a monomer of glucose and a monomer of galactose joined together by a beta 1,4 glycosidic bond

Question 19

To be metabolized for energy, the glycosidic bond of lactose must be cleaved by the enzyme lactase to release the 2 monomeric units. If you lack this enzyme, you are said to be _____ ______.

Answer 19

Lactose intolerant

Question 20

Describe the structure of sucrose, indicating which monomers it is made up of.

Answer 20

Sucrose consists of a monomer of glucose (in the alpha configuration) and a monomer of fructose (in the beta configuration) joined together by a glycosidic bond.

Question 21

Where do we acquire most of our dietary sucrose?

Answer 21

From plant material. Sucrose is the major form of carbohydrate in plants.

Question 22

Define homoglycan.

Answer 22

A homoglycan is a polysaccharide that contains only 1 type of monosaccharide subunit repeating over and over.

Question 23

Define heteroglycan.

Answer 23

A heteroglycan is a polysaccharide that contains more than 1 type of monosaccharide subunit

Question 24

In plants and fungi, glucose is stored as _______.

In animals, glucose is stored as _______.

Answer 24

Starch, glycogen

Question 25

Name the branched form of starch.

Answer 25

Amylopectin

Question 26

Name the linear form of starch.

Answer 26

Amylose

Question 27

Due to the configuration and shape of the glucose monomers, amylose forms a (left, right)-handed helical structure.

Answer 27

Left.

Question 28

Amylose consists of glucose monomers attached by what kind of repeating linkage?

Answer 28

Alpha 1,4

Question 29

Amylopectin consists of glucose monomers attached by what kind of linkage?

Answer 29

Alpha 1,6

Question 30

What creates the kinked branch points within the amylopectin structure?

Answer 30

The alpha 1,6 linkages between glucose subunits

Question 31

Glycogen is most similar to which form of starch? Amylose or amylopectin?

Answer 31

Amylopectin. Glycogen is much more branched, however.

Question 32

Why is polymerizing glucose an important way to store excess glucose for future metabolism?

Answer 32

It reduces the effective osmotic pressure of keeping glucose in the monomeric form.

Question 33

What role do glycosaminoglycans typically play in the body?

Answer 33

Structural roles. Not directly used for energy production.

Question 34

Glycosaminoglycans can undergo a variety of changes. What purpose does this serve? Or rather, why is it beneficial for the body that glycosaminoglycans can be so heavily modified?

Answer 34

Allows for the creation of new materials for usage in connective tissue and other places in the body

Question 35

When sugars covalently attach to proteins, we refer to the protein as a ______ ________.

Answer 35

Glycosylated protein.

Question 36

When do complex glycosylation patterns occur on a protein?

Answer 36

Post-translationally

Question 37

(T/F) Most secreted proteins aren’t glycosylated.

Answer 37

False. Often, the specific glycosylation patterns on membrane proteins at the cell surface are important for cell-to-cell recognition in the body.

Question 38

The presence of glycosaminoglycans allows cartilage to do what essential function? Name a location in the body where this essential function is most relevant.

Answer 38

Allows cartilage to adopt a gel-like structure that can absorb a lot of water molecules. This structure gives cartilage the ability to compress and absorb a lot of pressure. Can release water and then spring back by re-absorbing water after the pressure is removed. Important for its function in joints.