Carbohydrates

Question 1

name functions of carbohydrates

Answer 1

dietary calories
storage
cell membrane components
building blocks
mediate signaling

Question 2

what is a glycome?

Answer 2

the full set of carbohydrates produced by an organism

Question 3

between what do glycosidic bonds form?

Answer 3

anomeric carbon and the oxygen of an alcohol (release water)

Question 4

what type of bond is the glycosidic linkage?

Answer 4

covalent bond

Question 5

what are the glycosyltransferases?

Answer 5

enzymes catalyzing the formation of glycosidic bonds

Question 6

what are 2 ways to classify monosaccharides?

Answer 6

according to the number of carbon atoms
based on the carbonyl group (aldehydes or ketone)

Question 7

what are isomers?

Answer 7

compounds with the same chemical formula but different structure

Question 8

what are epimers?

Answer 8

carbohydrate isomers that differ in configuration around a specific carbon
cause for stereoisomer formation

Question 9

what are enantiomers?

Answer 9

type of isomerism in pairs of structures that are mirror images (OH group on left or right)

Question 10

what are Fischer projections?

Answer 10

2D representation of a 3D organic molecule by projection

Question 11

what is a hemiacetal?

Answer 11

product of aldehyde + alcohol to form a ring

Question 12

what is a hemiketal?

Answer 12

product of ketone + alcohol to form a ring of sugar

Question 13

describe pyranose formation

Answer 13

glucose cyclizes into a hemiacetal pyranose ring

Question 14

describe furanose formation

Answer 14

fructose cyclizes into a hemiketal furanose ring

Question 15

what are anomers?

Answer 15

occur when the OH group can freely interconvert between a and b forms in aqueous solutions

Question 16

What are Haworth projections?

Answer 16

a simple depiction of carbohydrates without the carbon atoms in the ring being written

Question 17

What is the limitation of Haworth projections?

Answer 17

they suggest that molecules are planar

Question 18

What are the 2 classes of conformation of pyranose rings?

Answer 18

chair and boat
difference in the tetrahedral geometry if saturated carbon atoms

Question 19

role of sugars in phosphorylation

Answer 19

phosphorylated sugars appear as intermediates in metabolism for breaking down glucose and ts synthesis

Question 20

what modification is the amino sugars?

Answer 20

the replacement of the hydroxyl group with an amino group
further acetylated into N-acetyl sugars
eg. glucosamine (N-acetylglucosamine)

Question 21

What happens to oxidized sugars

Answer 21

the carbonyl and hydroxyl groups can be oxidized
yield uronic acids (sugars that have the COOH group)

Question 22

What happens to reduced sugars

Answer 22

the carbonyl and hydroxyl groups, yield eg. xylitol
reduction by ribonucleotide reductase:
-converts ribose into deoxyribose

Question 23

what is a modification using glycosidic bonds?

Answer 23

anomeric carbon of glucose + oxygen of alcohol –> a glyoside

Question 24

What are disaccharides?

Answer 24

2 sugars joined by an O-glycosidic bond

Question 25

Describe sucrose

Answer 25

alpha glucose + beta fructose
can be cleaved by the enzyme sucrase
in sugar cane and sugar beets

Question 26

describe lactose

Answer 26

glucose + galactose via a b-1,4-glycosidic bond
in humans: hydrolyzed by lactase
in bacteria: hydrolyzed by b-galactosidase
in milk

Question 27

describe maltose

Answer 27

glucose + glucose via a-1,4-glycosidic bond
from starch and glycogen hydrolysis

Question 28

commonalities in sucrose, lactose, and maltose

Answer 28

are located on the outer surfaces of epithelial cells lining the small intestine
their cleavage products (ie glucose) provide energy as ATP