Chapter 10- Carbohydrates

Question 1

Monosaccharides

Answer 1

• The simplest carbohydrates
• aldehydes or ketones that have two or more hydroxyl groups.
• referred to as “oses” by # of carbons (triose, tetrose, pentode, etc.)
• aldoses contain an aldehyde, whereas ketoses such as fructose contain a keto
• the D & L isomers are determined by the configuration of the asymmetric carbon farthest from the aldehyde or keto group
• common monosaccharides: Ribose, deoxyribose, glucose, mannose, galactose, fructose

Question 2

Many common sugars exist in cyclic forms

Answer 2

The chemical basis for ring formation is that an aldehyde can react with alcohol to form a hemiacetal

Aldehyde: the resulting cyclic hemiacetal called pyranose bc of similarity to Pyran (6 member ring)

Ketone: can also react with alcohol to form hemiketal called furanose bc of similarity to Furan (5 member ring)

Question 3

Monosaccharides are joined to alcohols and amines through Glycosidic bonds

Answer 3

• three common reactants: alcohols, amines, phosphates
• a bond between glucose and the oxygen atom of alcohol is called an O-glycosidic bond an the resulting product is called a glycoside. Can also be linked to nitrogen to be called an N-glycosidic bond
• can also form an ester linkage to phosphates

Question 4

Monosaccharides are linked to form complex carbohydrates

Answer 4

Because sugars contain many hydroxyl groups, glycosidic bonds can join one monosaccharide to another.

-they are synthesized through the action of specific enzymes: glycosyltransferases

Question 5

Common Disaccharides

Answer 5

Sucrose, lactose, maltose

Consists of two sugars joined by an O-glycosidic bond

Question 6

Polysaccharides

Answer 6

Large polymeric oligosaccharides, formed by the linkage of multiple monosaccharides are called polysaccharides.

-if all the units in the polysaccharide are the same it is called a homopolymer: the most common in animal cells is glycogen (storage form of glucose). In plants, it is the homopolymer of starch: amylose and amylopectin.

Question 7

Cellulose

Answer 7

The other major polysaccharide of glucose found in plants, serves for structural role rather than nutritional. (Plant cell wall).

Cellulose is among the most abundant organic compounds in the biosphere
-umbra chef polymer of glucose joined by beta 1,4 linkages in contrast to alpha 1,4 seen in starch and glycogen.

Question 8

Carbohydrates attached to proteins

Answer 8

Form glycoproteins

• sugars are attached either to the amide nitrogen in the side chain of asparagine (N-linkage)
• or to the hydroxyl oxygen atom in the side chain of serine or threonine (O-linkage).
• This is a process called glycosylation

Question 9

Compare the number of reducing ends to non reducing ends in glycogen. At what end would you expect most metabolism to take place?

Answer 9

There is only one reducing end, but many non reducing ends

-you would expect it to take place at the non reducing ends because of the presence of only one reducing end and many non reducing ends to maximize the rate of degradation of glycogen and also the rate of synthesis

Question 10

Carbohydrates

Answer 10

The organic molecules with the molecular formula (CH2O)n and are literally carbon hydrates. Depending upon the number of n, they are mono or polysaccharides.

Question 11

Glycogen & cellulose different structures

Answer 11

Glycogen is the branched polymeric form of glucose joined together by alpha 1,4 linkages and branches are formed by alpha 1,6 glycosidic bonds once every 10 units.

Cellulose is the linear polymer form of glucose connected by beta 1,4 linkages.

Question 12

Glycoproteins

Answer 12

The proteins conjugated with carbohydrates.

3 classes: simple, proteoglycans, and mucoproteins

Question 13

Erythroprotein (EPO)

Answer 13

A hormone which is glycoprotein in nature.

Produced from the kidneys that help in the formation of red blood cells in bone marrow.