MMT: Carbohydrates I and II

Question 1

define monosaccharides and name the major examples of monosaccharides

Answer 1

one sugar; glucose, galactose, fructose, mannose

Question 2

define disaccharide and name the major examples of disaccharides

Answer 2

two sugars linked with an o-glycosidic linkage; sucrose, lactose, maltose, trehalose

Question 3

define polysaccharide and name the major examples of polysaccharides

Answer 3

10+ sugars linked with an o-glycosidic linkage; glycogen starch, cellulose

Question 4

what are two examples of heteropolysaccharides?

Answer 4

chitin and hyaluronic acid

Question 5

name the major metabolic fates of glucose

Answer 5

becoming glycolipids and glycoproteins, entering the pentose phosphate pathway, glycolysis, becoming glycogen, and becoming amino acids

Question 6

define aldose and ketose

Answer 6

an aldose in a carbohydrate with an aldehyde group at C-1, a ketose is a carbohydrate with a ketone group at C-2

Question 7

name the secondary metabolic fates of glucose (via acetyl CoA)

Answer 7

entering the Kreb’s cycle, fatty acid synthesis, cholesterol synthesis

Question 8

“-ulose” describes what kind of sugar

Answer 8

ketose

Question 9

what is a constitutional isomer?

Answer 9

two structures with the same molecular formula but different connectivity

Question 10

what is a stereoisomer? give the two examples.

Answer 10

two structures with the same molecular formula, same atomic connectivity, but different spatial arrangement.

a) enantiomers are mirror images
b) diastereomers are not mirror images

Question 11

define asymmetric center, penultimate carbon, and anomeric carbon

Answer 11

1. asymmetric center: a carbon with 4 different groups attached
2. penultimate carbon: the asymmetric carbon furthest from the aldehyde or keto group
3. anomeric carbon: carbon #1/asymmetric carbon in a haworth projection

Question 12

describe hemiacetal, hemiketal, and acetal linkages

Answer 12

1. a hemiacetal linkage occurs when a structure with an aldehyde forms a ring. the structure will have one OR group, and H group, and an R group
2. a hemiketal linkage occurs when a structure with a ketone forms a ring. the structure will have one OR group, one OH group, and two R groups
3. an acetal linkage occurs when two sugars are bound together, as opposed to binding with itself. in the case of sugars, it will be an o-glycosidic linkage

Question 13

what determines a D vs L configuration in carbohydrates?

Answer 13

the position of the OH group on the penultimate carbon. if it is facing right it is D, left it is L.

Question 14

what determines alpha vs beta configuration in carbohydrates?

Answer 14

if the OH group attached to the anomeric carbon is on the opposite side of the plane of the ring from C6, it is alpha. if it is on the same side, it is beta.

beta and same have four letters each!

Question 15

glucopyranose exists in alpha, beta, and open-chain forms. name the relative concentrations of each at equilibrium.

Answer 15

alpha :about 1/3
beta: about 2/3
open chain: less than 1%

Question 16

describe free aldehyde formation observed in glucose rings. why does it happen? what are the potential consequences?

Answer 16

in solution, glucose can reversibly form a free aldehyde at carbon 1. the opening and closing of the ring due to this reaction allows for the formation of alpha and beta anomers freely and without use of an enzyme. however, the free aldehyde group can also irreversibly form advanced glycation end products with proteins.

Question 17

describe how advanced glycation end products are formed and the issues with them

Answer 17

they are formed when sugar levels are high. when this happens, the free aldehyde in an open chain glucose can react with other molecules irreversibly and without enzymatic regulation. this can cause the unfolding of proteins, and lead to effects typically associated with aging (crows feet, wrinkles, etc.)

Question 18

structurally, what makes A and B antigens different from each other and the O antigen?

Answer 18

The A antigen has an additional GalNAc, and the B antigen has an additional galactose. The O antigen just contains the common core.

Question 19

If a patient has blood type A, what antibodies are present? What if they have B? O?

Answer 19

A: B antibodies
B: A antibodies
O: A and B antibodies

Question 20

Describe Hemolytic disease of the fetus and newborn (HDFN) in basic terms

Answer 20

this occurs when the mother and fetus have incompatible blood types. the mother must be exposed to the antigen previously for the issue occur. this will lead to the mother developing antibodies that will cross the placenta and interact with fetal RBC and cause hemolysis.

Question 21

In HDFN, how can a mother be exposed to an incompatible blood type?

Answer 21

mom can be exposed to an antigen via transfusion, fetomaternal bleeding, or shared needles

Question 22

what is the treatment for HDFN?

Answer 22

typically, no intervention required. mom and baby can become anemic and build up billiruben, but typically mom’s will clear up and baby can be treated with blue light.

Question 23

which monosaccharides are found in sucrose? what is the general linkage pattern?

Answer 23

glucose and fructose
alpha (1,2) > beta

Question 24

which monosaccharides are found in lactose? what is the general linkage pattern?

Answer 24

galactose and glucose
beta (1,4) > alpha

Question 25

which monosaccharides are found in maltose? what is the general linkage pattern?

Answer 25

two glucose molecules
alpha (1,4) > alpha

Question 26

can sucrose, lactose, and maltose form a free aldehyde?

Answer 26

lactose and maltose can, sucrose cannot. sucrose can’t because both of the anomeric carbons are locked in position via the glycosidic linkage.

Question 27

what ion can be used to determine the presence of reducing sugars? how?

Answer 27

Cu 2+
the copper can oxidize the free aldehyde to a carboxyl group

Question 28

what are reducing and non-reducing ends in a molecule?

Answer 28

the reducing end involves a free aldehyde, whereas the non-reducing end does not.

Question 29

where in the body do we find disaccharidases? what are the examples?

Answer 29

in the brush border (microvilli) of the small intestine; sucrase, maltase, isomaltase (these three can also work as sucrase-isomaltase), and lactase

Question 30

what is sucralose? what can out body do with it?

Answer 30

sucralose is a chlorinated derivative of sucrose. our bodies cannot do anything with it, as our bodies cannot break it down. it passes through the GI tract unchanged.

Question 31

of the disaccharidases, which is most sensitive to disruption? what are the consequences?

Answer 31

lactase; deficiency in the enzyme can occur with age, or temporarily due to infection or inflammation. lacking the enzyme leads to accumulating undigested lactose, causing bloating, gas, cramps, etc.

Question 32

how can lactose intolerance be diagnosed?

Answer 32

a hydrogen breath test

Question 33

what is the major dietary source of galactose?

Answer 33

lactose

Question 34

how is maltose formed? what enzyme can hydrolyze it?

Answer 34

it is a product of starch and glycogen digestion in the small intestine; maltase, a digestive enzyme

Question 35

how is isomaltose formed? what enzyme can hydrolyze it?

Answer 35

it is a product of starch and glycogen digestion in the gut. it contains an alpha 1,6 linkage that can be broken by isomaltase found in the brush border of the small intestine.

Question 36

describe a-amylase

Answer 36

a pancreatic enzyme that hydrolyzes polysaccharides

Question 37

where is starch found

Answer 37

in plants as a storage form of glucose

Question 38

describe the two major components of starch

Answer 38

1. amylose: an unbranched, linerar glucose polymer linked via a-1,4 glycosidic linkages
2. amylopectin: a branched polymer of glucose containing a-1,4 and a-1,6 linkages

Question 39

where is cellulose found?

Answer 39

in plants as a strucutral component

Question 40

describe the composition of cellulose. why is it special?

Answer 40

cellulose is an unbranched polymer containing b-1,4 glycosidic linkages. the beta configuration allows for straight chains that can interact and form fibrils. humans cannot break the b-1,4 link as we do not have the enzyme, so we cannot digest it.

Question 41

where is glycogen found?

Answer 41

in the liver and skeletal muscle of humans/animals as the storage form of glucose

Question 42

describe the structure of glycogen

Answer 42

similar to amylopectin, it contains a-1,4 and a-1,6 linkages, but it is more branched than amylopectin.

Question 43

define a glycosaminoglycan (GAGs)

Answer 43

repeating disaccharide units of amino sugars that can link to proteins to form proteoglycans. they are typically associated with the cell surface and extracellular matrix

Question 44

name the big examples of proteoglycans

Answer 44

heparin, dermatan sulfate, hyaluronate, chondroiton 6-sulfate, keratan sulfate

Question 45

describe hurler syndrome: which enzyme is involved, what happens biochemically, what are the effects?

Answer 45

a deficiency in the lysosomal enzyme a-L-iduronidase, which removes unsulfated iduronic acid residues during the recycling of heparan sulfate and dermatan sulfate. these two glycosaminoglycans then build up. this can cause developmental delay, gargoylism, corneal clouding, airway obstruction, and hepatosplenomegaly

Question 46

what is the treatment for hurler syndrome?

Answer 46

hematopoietic stem cell transplant and enzyme replacement therapy. the enzyme does not cross the blood-brain barrier, so introducing it does not alleviate cognitive dysfunctions

Question 47

briefly explain how high carbohydrate intake can lead to obesity

Answer 47

high carbohydrate intake will lead to high glucose, which induces hyperinsulinism. insulin is anabolic in nature, and thus promotes fat synthesis.

Question 48

briefly explain why obesity leads to diabetes type 2

Answer 48

obesity increases insulin demand, and the pancreas cannot supply enough

Question 49

why is hemoglobin A1c a good measurement for glucose levels?

Answer 49

it can be used to track glucose levels over time; the free aldehyde form of glucose can react with hemoglobin to form HbA1c. HbA1c concentration, as a result, is proportional to the amount of glucose in the blood. this could show previous episodes of hyperglycemia.

Question 50

does the glycation of hemoglobin impact its oxygen carrying ability?

Answer 50

no

Question 51

Hemoglobin A1C is formed between glucose and which of the functional groups in hemoglobin?

Answer 51

amino group