Carbohydrate Structure & Function

1.

Open Ended

30 sec

1 pt

What are carbohydrates? What are their functions?

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Answer explanation

Carbohydrates are the most abundant biological molecules, function as energy source (glucose), structural component (cellulose/chitin/proteoglycans), and act as a precursor for biosynthesis (nucleotides/amino acids/fatty acids).

2.

Open Ended

30 sec

1 pt

Carbohydrates can be classified by the number of sugars present and their size, what are the three types of sugar classifications?

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Answer explanation

Monosaccharide:one pure sugar Oligosaccharide: 2-10 sugars linked by glycosidic bond Polysaccharide: More than 10 sugars linked by glycosidic bond

3.

Open Ended

30 sec

1 pt

What is the structure of a monosaccharide?

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Answer explanation

Polyhydroxyaldehyde or polyhydroxyketones, range from 3-9 carbons with an attached carbonyl group.

4.

Open Ended

30 sec

1 pt

How do you find the number of isomers a sugar has?

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Answer explanation

2^n n= # of chiral carbons

5.

Open Ended

30 sec

1 pt

Know the structure of glyceraldehyde,ribose,glucose, frutcose

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Answer explanation

...

6.

Open Ended

30 sec

1 pt

What are enantiomers?

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Answer explanation

Stereoisomers that are mirror images (D & L forms).

7.

Open Ended

30 sec

1 pt

What are diastereomers?

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Answer explanation

Stereoisomers that are not enatiomers (not mirror images).

8.

Open Ended

30 sec

1 pt

What are epimers?

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Answer explanation

Paticular type of diastereomer that differ in the configuration around one chiral carbon.

9.

Open Ended

30 sec

1 pt

What is required to change stereochemisty?

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Answer explanation

Enzymes, because covalent bonds must be broken and reformed.

10.

Open Ended

30 sec

1 pt

Sugars of 5 carbons or more usually exsist in a cyclic form, why does this occur?

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Answer explanation

Energetically more stable, the carbonyl carbon reacts with an alcohol to form either a hemiketal or hemiacetal through an intramolecular bond to form cyclic structure.

11.

Open Ended

30 sec

1 pt

Formation of a hemiketal or hemiacetal causes the carbonyl carbon to become chiral, what is this carbonyl carbon now called? What about the isomers around it?

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Answer explanation

Anomeric Carbon the isomers are now anomers

12.

Open Ended

30 sec

1 pt

What are anomers?

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Answer explanation

Two isomeric sugars that are cyclic, and only differ in the position of the -OH group attached to the hemiacetal carbon.

13.

Open Ended

30 sec

1 pt

There are two types of anomers, dependent on the position of the hydroxyl group on the carbonyl carbon (C1), what are they called? How do you differentiate the two?

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Answer explanation

alpha & beta alpha-methoxyl group and hydroxyl group are on opposite sides (points down) beta-methoxyl group and hydroxyl group are on the same side (points up)

14.

Open Ended

30 sec

1 pt

What is mutorotation?

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Answer explanation

Chemical reactions that may result in the isomerization of the α and β isomers of simple sugars. "interconversion of anomers" (does not require enzyme)

15.

Open Ended

30 sec

1 pt

Oxidizing the -OH group at the C6 position of a monosaccharide (oxidation reaction) produces?

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Answer explanation

a uronic acid, adds a (-) charge.

16.

Open Ended

30 sec

1 pt

Oxidizing the carbonyl group of a monosaccharide (oxidation reaction) produces?

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Answer explanation

an aldonic acid

17.

Open Ended

30 sec

1 pt

What is a reducing sugar?

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Answer explanation

Sugars that have carbonyl groups tha can become oxidized, as these groups are oxidized something else is "reduced".

18.

Open Ended

30 sec

1 pt

What is the Benedict's test?

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Answer explanation

Measuring the amt. of sugar you have by adding something that will be reduced and measuring how much reduction has occured. (basis for urine test strips)

19.

Open Ended

30 sec

1 pt

In reference to oligosaccharides and polysaccharides, which end is the reducing end?

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Answer explanation

The end with a carbonyl group

20.

Open Ended

30 sec

1 pt

What is a glycosidic bond?

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Answer explanation

Reaction of a hemiacetal/hemiketal with an alcohol, forms a bond between sugar molecules.Another name for a glycosidic bond is an acetal or ketal bond. Can form either "o-glycosidic bonds" or "n-gylcosidic bonds"

21.

Open Ended

30 sec

1 pt

What are the consequences of forming a glycosidic bond?

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Answer explanation

anomeric configuration is now stable, mutorotation can no longer occur, carbonyl carbon involved in a glycosidic bond can no longer be oxidized.

22.

Open Ended

30 sec

1 pt

What are glycosyltransferases?

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Answer explanation

enzymes that catalyze glycosylation reactions, they are specific for sugars and anomeric linkages.

23.

Open Ended

30 sec

1 pt

Sugar polymer synthensis has no template, what is it dependent on?

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Answer explanation

dependent on the expression of different gylcosyltransferases

24.

Open Ended

30 sec

1 pt

What is cellulose?

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Answer explanation

glucose polymer with beta 1,4 anomeric linkage, found in plant cell walls.

25.

Open Ended

30 sec

1 pt

What is amylopectin and glycogen?

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Answer explanation

glucose ploymers with an alpha 1,4 anomeric linkage. Glycogen is the glucose storage form in mammals, amylopectin is a component of startch, the glucose storage form of plants.

26.

Open Ended

30 sec

1 pt

What is chitin?

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Answer explanation

homopolysaccharide of GlcNac, structural component of cell wall in fungus and exoskeleton of insects. Being explored as a drug delivery mechanism.

27.

Open Ended

30 sec

1 pt

What are glycoconjugates?

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Answer explanation

they are heteropolysaccharides (more than one type of sugar in a polysaccharide). glucose that is linked to something else usually lipid/protein

28.

Open Ended

30 sec

1 pt

What's glycan synthesis dependent on?

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Answer explanation

does not require a template, enzyme mediated synthesis (glycosyltransferase), structure depends on enzyme expression, specificity, and substrate availability.

29.

Open Ended

30 sec

1 pt

What are glycans?

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Answer explanation

simple polysaccharides only consists of one type of sugar

30.

Open Ended

30 sec

1 pt

Glycoforms are different forms of the same glycoprotein/glycolipid/proteoglycan, an example of this is ABO blood type, what are the differences between the four blood types.

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Answer explanation

A & B blood types have 2 different glycosyltransferases, AB has a combination of both enzymes, and O blood doesnt have these paticular enzymes at all.

31.

Open Ended

30 sec

1 pt

What are N-linked glycoproteins?

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Answer explanation

sugars form an n-glycosidic bond with the amide bond of asparigine. Gylcosylation occurs cotranslationally (as the protein is being synthesized) in the ER and processing occurs in the golgi.

32.

Open Ended

30 sec

1 pt

N-linked glycoproteins form three types of structures, what are they?

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Answer explanation

1. high mannose 2.complex (many different sugars) 3.hybrid (branched with one high mannose and one complex)

33.

Open Ended

30 sec

1 pt

What are O-linked glycoproteins?

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Answer explanation

sugars form an o-glycosidic bond to theronine/serine. Glycosylation is post-translational, sugars are added singally, more dependent on glycosyltransferases than n-linked.

34.

Open Ended

30 sec

1 pt

O-linked glycoproteins form what kind of structures?

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Answer explanation

forms rather short (<10) oligosaccharide with branched structure.

35.

Open Ended

30 sec

1 pt

Functions of n & o-linked glycosylation?

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Answer explanation

1. limit confirmational freedom of the protein, stiffen polypeptide chain (o-linked) 2. Soubility/stability, make more water soluble & protect the backbone from proteases. 3. Protein localization, lysosomal enzymes etc

36.

Open Ended

30 sec

1 pt

What is a gylcosaminoglycan (GAG)?

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Answer explanation

sugar component of proteoglycan, linear chain of repeating disaccharide unit. One sugar is n-acetylhexosamine, other sugar usually glucuronic acid/iduronic acid. Have highly charged sulfate chains.

37.

Open Ended

30 sec

1 pt

Proteoglycans are defined by what?

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Answer explanation

type of GAG chain, type of protein core, & function.

38.

Open Ended

30 sec

1 pt

Two primary types of proteins that bind glycans?

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Answer explanation

glycosylaminoglycans & lectins

39.

Open Ended

30 sec

1 pt

What are selectins?

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Answer explanation

A protein, expressed by endothelial cells, that binds carbohydrate structures on white blood cells.

40.

Open Ended

30 sec

1 pt

What are lectins?

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Answer explanation

proteins that recognize oligosaccharides of n & o-linked glycoproteins, bind glycans.

41.

Open Ended

30 sec

1 pt

Charactestics of a glycan to protein interaction?

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Answer explanation

interaction has low affinity (need multiple interactions) & selectivity is dependent on non covalent interactions (hbonds,van der Waals, electrostatic interactions).

42.

Open Ended

30 sec

1 pt

Heparin is widely used as an injectable anticoagulant. what are the characteristics of the structure of heparin?

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Answer explanation

Heparin works by binding to antithrombin III which activates it & stops the blood clotting mechanism. -It is highly negatively charged with many sulfate groups. -The sugar resides comprising the structure are derivatives of glucose.

43.

Open Ended

30 sec

1 pt

Stereoisomers?

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Answer explanation

2 or more structures with the same ligands but only differ by the spatial arrangement of those ligands around a chiral carbon.

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