Biochemistry Chapter 11

Question 1

What are the simplest carbohydrates?

Answer 1

Monosaccharides

Question 2

What are monosaccharides?

Answer 2

• monosacchardies are aldehydes or ketones that contain two or more hydroxyl groups
• Monosaccharides can be linked together to form a large variety of oligosaccharide structures
• exist in many isomeric forms
• simple sugars that cannot be hydrolyzed to simpler compounds

Question 3

what are the smallest monosaccharides composed of?

Answer 3

Three carbons!!
-dihydroxyacetone (ketone)
-D glyceraldehyde (aldose)
-L glyceraldehyde (aldose)

Question 4

What are common Monosaccharides?

Answer 4

• D-Ribose
• D-Deoxyribose
• D-Glucose
• D-mannose
• D-Galactose
• D-Fructose

Question 5

Which is a constitutional isomer?

Answer 5

Dihydroxyacetone and glyceraldehyde

Question 6

which is a stereoisomer?

Answer 6

D-glyceraldehyde and L- glyceraldehyde

Question 7

Hemiacetal

Answer 7

Aldehyde and alcohol

Question 8

Hemiketal

Answer 8

Ketone and alcohol

Question 9

In the case of glucose, the hemiacetal, a …… carbon ring, is called a ….

Answer 9

six
pyranose

Question 10

In the case of Ketose fructose, the hemiketal a … carbon ring is called a …..

Answer 10

five
furanose

Question 11

An additional asymmetric center is created when a cyclic hemiacetal is formed, generating yet another diastereoisomeric form of sugars called

Answer 11

anomer

Question 12

the a form means that the hydroxyl at C-1 is…..

Answer 12

below the plane of the ring

Question 13

the B form means that the hydroxyl at C-1 is…

Answer 13

above the plane of the ring

Question 14

Fructose forms borth the ….. and ……. form

Answer 14

-pyranose
-furanose

Question 15

what two conformations can pyranose form

Answer 15

baot and chair

Question 16

chair form has two orientations

Answer 16

axial and equatorial

Question 17

why does B-D glucopyranose adopt the chair form?

Answer 17

B-D glucopyranose adopts the chair conformation because the axial positions are occupied by hydrogens, reducing steric hindrance

Question 18

glucose is a reducing sugar

Answer 18

• A solution of glucose contains one third a anomer, two thirds B anomer, and about 1% open chain

Question 19

reducing agent

Answer 19

Sugars that react with oxidizing agents are called reducing sugars, whereas those that do not are non reducing sugars

Question 20

open chain glucose can react with …., reducing the …. while itself becoming oxidized

Answer 20

-Cu2+
-copper

Question 21

less than 6% of hemoglobin is glycosylated

Answer 21

nondiabetic people

Question 22

almost 10% of hemoglobin is glycosylated

Answer 22

uncontrolled diabetes

Question 23

As a reducing sugar, glucose can react with amino groups, often …… residues in proteins

Answer 23

lys or arg

Question 24

glucose can react with hemoglobin, forming …

Answer 24

glycosylated hemoglobin (Hemoglobin A1c), which is fully functional

Question 25

Advanced glycation end products (AGEs)

Answer 25

Following the primary modification, cross-linking may occur between the site of the first modification and elsewhere in the protein, further compromising function. These modifications, known as advanced glycation end products (AGEs), have been implicated in aging, arteriosclerosis, and diabetes, as well as other pathological conditions.

Question 26

Monosaccharides are joined to alcohols and amines through glycosidic bonds

Answer 26

A bond formed between the anomeric carbon atom and oxygen atom of an alcohol is called an O-glycosidic bond

Question 27

What is a bond formed between the anomeric carbon atom and an amine is called an

Answer 27

N-glycosidic bond

Question 28

Phosphorylated sugars

Answer 28

Phosphorylated sugars are key intermediates in energy generation and Biosynthesis

Question 29

phosphorylation

Answer 29

• Phosphorylation is a common modifications of carbohydrates
• Phosphorylation makes the sugar anionic and prevents them from leaving the cell
• Phosphorylation also facilitates the metabolism of sugars

Question 30

monosaccharides are linked to form complex carbohydrates

Answer 30

ogliosaccharides containing two or more monosaccharides are linked by O-glycosidic bonds

Question 31

sucrose, lactose and maltose are the common disaccharides

Question 32

sucrose

Answer 32

Sucrose is obtained from sugar cane and sugar beets and is composed of a glucose linked to a fructose. The linkage is A for glucose and B for fructose. Sucrose is cleaved by sucrase (also called invertase)

Question 33

lactose

Answer 33

Lactose is the disaccharide of milk that consists of a galactose linked to a glucose by a B-1,4 linkage. Lactase cleaves lactose.

Question 34

maltose

Answer 34

Maltose, a degradation product of large oligosaccharides, is composed of two glucose molecules linked by an a-1,4 linkage. Maltose is hydrolyzed by maltase.

Question 35

what are the storage forms of glucose

Answer 35

glycogen and starch

Question 36

what is the glucose storage form in animals

Answer 36

polysaccharide glycogen

Question 37

most glucose units in glycogen are linked by …….. with branches formed by ……… about every …. glucose untis

Answer 37

• a-1-4 glycosidic bonds
• a-1-6 glycosidic bonds
• 12

Question 38

in plants, glucose is stored as …. of which there are two forms

Answer 38

starch

Question 39

amylose

Answer 39

Amylose is a linear polymer of glucose units linked by a-1,4 glycosidic bonds

Question 40

amylopectin

Answer 40

Amylopectin is a branched polymer, with an a-1,6- glycosidic bond for every 30 a-1,4-glycosidic bonds

Question 41

cellulose

Answer 41

• cellulose is a structural component of plants and is made of chains of glucose
• homopolymer linked by B-1,4-glycosidic bond
• the b linkage yields a straight chain capable of interacting with other cellulose molecules via H bonds to form strong fibris
• the a-linkages of starch and glycogen form compact hollow cylinders suitable for accessible storage

Question 42

insoluble and soluble fiber are an important part of the diet

Answer 42

• mammals cannot digest cellulose, but it is still useful in the diet increasing the rate at which digestion products pass through the large intestine
• soluble fibers such as polygalacturonic (pectin) also aid in the digestion, faciltating absorption of nutrients from the diet

Question 43

human milk oligosaccharides protect newborns from infection

Answer 43

• more than 150 different oligosaccharieds have been identified in human milk, with the composotion and amount varying in women
• these are NOT digested by the infants but play a protective role against bacterial infection
• milk oligosacchardies appear to prevent the growth of certain streptococcus bacteria, which may otherwise be transferred from the mothers vaginal epithelium and caue pneumonia, blood positing or meningtisis in the infant

Question 44

what are the three main classes of glycoproteins?

Answer 44

• Glycoproteins
• proteoglycans
• mucins or mucoprotiens

Question 45

glycoproteins

Answer 45

• protein by weight
• membrane proteins
• cell adhesions
• binding of sperm and egg

Question 46

proteoglycans

Answer 46

• carbohydrates by weight
• play structural role or act as lubricants
• attached to glycosaminoglycan