BIOCHEMISTRY - CLUTCH CH. 9 - CARBOHYDRATESlightcat-files.s3.amazonaws.com/packets/biochemistry-17-clutch... · CONCEPT: CARBOHYDRATES Carbohydrates: structurally & functionally diverse,

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BIOCHEMISTRY - CLUTCH

CH. 9 - CARBOHYDRATES

CONCEPT: CARBOHYDRATES

●Carbohydrates: structurally & functionally diverse, carbon-based-molecules rich in _______________ groups (-OH).

□ Also referred to as ___________________, the Greek word meaning “sugars”.

●When “_____________________” was originally coined, it referred to compounds with the formula Cn(H2O)n, where n ≥ 3.

□ ___________ carbohydrates: fit Cn(H2O)n formula exactly.

□ ___________ carbohydrates: can slightly differ from Cn(H2O)n & can also have ____, N or S atoms too.

PRACTICE: Which of the following chemical formulas represents that of a simple carbohydrate?

a) C2H2O2. b) C6H12O6. c) C5H4O3. d) C3H6O9.

3 Size Classes of Carbohydrates

1) _________saccharide: a single carbohydrate unit (or ______________).

2) _________saccharide: 2 to ~_______ covalently linked monosaccharides.

3) _________saccharide: _____ 20 covalently linked monosaccharides.



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CONCEPT: CARBOHYDRATES

Proteins vs. Carbohydrates

PRACTICE: Which of the following is a monosaccharide?

Intro to Carbohydrate Functions

●Recall: Carbohydrates have incredibly diverse biological functions including acting-as/participating-in:

□ Short-term ___________ Sources: carbohydrate oxidation is the central energy-yielding pathway in most cells.

□ ____________ & Protective Components: carbs make up part of nucleotide structures & plant/bacterial cell walls.

□ Cell ___________________: carbohydrates participate in cell recognition/adhesion/coordination.

□ Designate Intracellular __________________: carbohydrate modifications can determine area & metabolic fates.



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CONCEPT: MONOSACCHARIDES

●Recall: monosaccharides are individual carbohydrate _____________ & the simplest form of sugar.

□ Names generally end with the suffix “-_______” (ex. glucose).

□ Monosaccharides can be _______________ in several different ways.

Aldoses or Ketoses

●Monosaccharides can be classified into ______ groups based on the nature of their carbonyl group:

1) _____________: a sugar whose carbonyl group is an ________________ (-CHO).

2) _____________: a sugar whose carbonyl group is a _____________.

EXAMPLE: Aldoses vs. Ketoses.

Monosaccharides Grouped By # of Carbons

●Monosaccharides are also grouped based on the number of their ____________ atoms.

□ Monosaccharides with 3, 4, 5, & 6 carbons are respectively _____oses, ______oses, ______oses & _____oses.

□ These prefixes can be preceded by “________-” or “________-” to respectively indicate an aldose or ketose.

EXAMPLE: Classify the following monosaccharides based on their number of carbon atoms & carbonyl groups.



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CONCEPT: MONOSACCHARIDES

PRACTICE: Select the appropriate label for each of the three following monosaccharides:

A) Arabinose: B) Threose: C) Erythrulose:

a) Aldopentose. a) Ketohexose. a) Aldotetrose.

b) Ketopentose. b) Aldopentose. b) Ketopentose.

c) Aldotetrose. c) Aldotetrose. c) Aldopentose.

d) Ketotetrose. d) Ketotetrose. d) Ketotetrose.

Assigning Numbers to the Carbons of Linear Monosaccharides

●Carbon atoms in linear monosaccharides are numbered based on positioning of the __________ group (aldehyde or ketone).

□ Carbonyl carbon atom part of the aldehyde or ketone should be assigned the ______________ possible number.

□ Numbered carbons are designated as C-1, C-2, C-3, etc.

EXAMPLE: Appropriately number the carbon atoms in the following linear monosaccharides.

PRACTICE: Number the carbon atoms in the following linear form of fructose below:



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# of Stereoisomers: ____________ # of Stereoisomers: ____________

CONCEPT: STEREOCHEMISTRY OF MONOSACCHARIDES

●Recall: WAY back in previous videos, we did Organic Chemistry review. Be sure to check those out before moving on!

●To represent 3D structures on paper, linear monosaccharides are commonly displayed using _____________ Projections.

Calculating # of Stereoisomers

●# of Stereoisomers a molecule has = ______ (where ____ = # of chiral carbons).

□ Recall: Chiral Carbon: a carbon atom covalently bound to ______ distinct chemical groups.

EXAMPLE: Circle all of the chiral centers and determine how many stereoisomers each of the following molecules have.

A) B)


Sugar

Shadow

Fischer

Projection



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1 2 3 4

PRACTICE: Which sugar is an enantiomer of sugar A? How many stereoisomers does sugar A have? ____________

a) None of them.

b) Sugar B only.

c) Sugar C only.

d) Sugar D only.

e) Both Sugars B and D.

Monosaccharide Epimers

●____________: diastereomers that differ ONLY in configuration of any one-single chiral carbon.

PRACTICE: Use the Fischer projections of the four monosaccharides below to answer the next two problems (A & B).

A) The term that best describes the relationship of all four sugars to each other is:

a) Diastereomers. b) Enantiomers. c) Epimers.

B) Sugars 2 and 4 are:

a) C1-epimers. d) C4-epimers.

b) C2-epimers. e) C5-epimers.

c) C3-epimers.




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●Review of the different types of monosaccharide isomers.

PRACTICE: Two sugars which differ from one another only in configuration of one of many chiral carbon atoms are termed:

a) Epimers. c) Optical isomers. e) Conformers.

b) Enantiomers. d) Stereoisomers. f) None of these are correct.




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PRACTICE: Amongst the aldopentoses shown below, identify the pairs that are enantiomers.

____ and ____

____ and ____

____ and ____

____ and ____

PRACTICE: Which term best describes the relationship between D-Mannose & L-Mannose?

a) Enantiomers. b) Anomers. c) Epimers. d) Diastereomers. e) Same molecules

PRACTICE: According to the Fischer projections of the following monosaccharides, circle the C-5 epimer of L-Talose?



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Standard Fischer Projection:

- Carbonyl group is on _______.

- ______________ carbon-chain is vertical.

CONCEPT: MONOSACCHARIDE CONFIGURATIONS

●Recall: configurations of monosaccharide chiral carbons can be designated using _______ different systems:

1) Cahn-Ingold-Prelog (____/____). 2) Fischer’s Convention (____/____).

1) R/S Configuration

●Cahn-Ingold-Prelog system designates absolute ____/____ configurations.

□ Assign priorities 1 4 (based on atomic _____________) to each chemical group attached to the chiral carbon.

□ Determine if priorities 1 2 3 (ignoring 4) are in a clockwise (____) or counter-clockwise (___) configuration.

□ Only if priority ____ is on a wedge (popping out of the page), assign the opposite configuration that it “looks like.”

EXAMPLE: Determine the Cahn-Ingold-Prelog (R/S) configurations for glyceraldehyde’s chiral center:

2) D/L Configuration

●Fischer’s Convention designates ____/____ configurations relative to ____________________ enantiomers.

□ ____ configuration = -OH group __________; usually D = ____ configuration.

□ ____ configuration = -OH group __________; usually L = ____ configuration.

●Monosaccharides have the same configuration as the _______________ numbered chiral carbon.

□ In other words, a monosaccharide’s configuration is that of the chiral carbon __________ from its carbonyl group.

EXAMPLE: Determine the Fischer Convention (D/L) configurations of the following glucose monosaccharides?

●Unlike biological amino acids (which are usually ___ configuration), biological carbohydrates are usually ___ configuration.

□ The reason why life prefers L-amino-acids but ____-carbohydrates is unknown.



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CONCEPT: MONOSACCHARIDE CONFIGURATIONS

PRACTICE: Identify the D/L and R/S configuration of all of the following monosaccharides:

a) ______ b) ______ c) ______ d) ______

PRACTICE: How many D-stereoisomers are possible for a D-ketopentose?

a) 4. b) 8. c) 24. d) 2. e) 16.

PRACTICE: Which TWO of the following traits apply to Fischer’s Convention for naming stereoisomers?

a) Utilizes (+) and (-) designations. d) Requires drawing the compound with aldehyde/ketone at the top.

b) Utilizes (D) and (L) designations. e) Based on optical properties of the compound in solution.

c) Utilizes (R) and (S) designations. f) Reflects stereochemistry at multiple centers.

PRACTICE: How many possible epimers of D-glucose exist?

a) 1. b) 2. c) 4. d) 6. e) 8. f) 16.



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Standard Haworth Projection:

- Anomeric carbon is on __________-side.

- Highest numbered carbon points _____.

CONCEPT: CYCLIC MONOSACCHARIDES

●Monosaccharides can cyclize to form many different rings, but 5 & 6-membered rings are most __________.

□ Furanose: monosaccharide with a ______-membered ring.

□ Pyranose: monosaccharide with a ______-membered ring.

Haworth Projections

●Cyclic monosaccharide structures are commonly depicted with ______________ Projections.

□ Darker/thicker lines pop out of the page, ____________ to us.

□ Lighter/thinner lines go into the page, ______________ away from us.

●Haworth projections can be misleading since cyclic monosaccharides are NOT planar (due to tetrahedral carbon bonds).



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Converting Fischer Projections to Haworth Projections

●Chemical groups pointing _________ of a Fischer Projection point ____________ in a Haworth Projection.

●Chemical groups pointing _________ of a Fischer Projection point ____________ in a Haworth Projection.

EXAMPLE: Convert the D-glucose Fischer Projection into the D-glucopyranose Haworth Projection.

Assigning Numbers to the Carbons of Cyclic Monosaccharides

●Carbon atoms in cyclic monosaccharides are numbered based on positioning of the _______________ carbon.

□ Anomeric carbon: only ring carbon covalently attached to ______ oxygen atoms.

□ Anomeric carbon should be assigned the ________________ possible number.

EXAMPLE: Appropriately number the carbon atoms in the following cyclic form of glucose below.

PRACTICE: Below is the structure for a cyclic D-monosaccharide. Which labeled carbon is the anomeric carbon?

a) A. b) B. c) C. d) D. e) E. f) F.



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PRACTICE: Which image represents the proper convention for carbon numbering of cyclic sugars?

a) A.

b) B.

c) C.

d) D.

PRACTICE: Which of the following is the correct Haworth projection of D-Gulose?

a) A.

b) B.

c) C.

d) D.



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CONCEPT: HEMIACETAL VS. HEMIKETAL

Cyclization of Monosaccharides

●Sugars cyclize via a nucleophilic addition reaction between an _____________ & an aldehyde/ketone.

□ Alcohols = ______________________ . □ Aldehydes & ketones = electrophilic.

□ Monosaccharide cyclization forms an ______________ carbon.

EXAMPLE: Alcohols react with aldehydes & ketones during monosaccharide cyclization.

Cyclization Forms Hemiacetals & Hemiketals

●Upon monosaccharide cyclization, the anomeric carbon becomes part of a relatively __________ hemiacetal or hemiketal.

□ Hemiacetals: half of an __________ group resulting from -OH + aldehyde.

□ Hemiketals: half of a __________ group resulting from -OH + ketone.

EXAMPLE: Hemiacetals & Hemiketals:

PRACTICE: Which of the following is a hemiketal?

a) A.

b) B.

c) C.

d) D.



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CONCEPT: HEMIACETAL VS. HEMIKETAL

PRACTICE: For monosaccharides to cyclize, an alcohol group must attack a carbonyl group within the same sugar.

A) Which carbon of the linear ketohexose shown below has the reactive carbonyl?

a) C1. b) C2. c) C3. d) C4. e) C5.

B) Upon cyclization, would a hemiacetal or hemiketal form?

a) Hemiacetal. b) Hemiketal.

PRACTICE: Use the image of the following glucose molecule to answer the questions.

A) Upon cyclization, which of the red circled carbons becomes the anomeric carbon?

a) A. b) B. c) C. d) D. e) E.

B) Upon cyclization, would a hemiacetal or hemiketal form?

a) Hemiacetal. b) Hemiketal.

PRACTICE: In the reaction shown below the compound on the far right is a:

a) Acetal.

b) Alcohol.

c) Ether.

d) Ester.

e) Hemiacetal.



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CONCEPT: ANOMER

Monosaccharide Cyclization Generates α and β Anomers

●________________: cyclic sugars that differ ONLY in configurations of their ______________ carbon.

□ Anomeric carbon: only ring carbon attached to ____ oxygens (used to be carbonyl carbon before cyclization).

●When a monosaccharide cyclizes, the anomeric carbon becomes a chirality center with ______ possible configurations:

1) ____ Anomer: anomeric carbon’s -OH is on the opposite side of its highest numbered carbon.

2) ____ Anomer: anomeric carbon’s -OH is on the _______ side of its highest numbered carbon.

EXAMPLE: Which of the following molecules are anomers?

a) Molecules 1 and 2.

b) Molecules 2 and 5.

c) Molecules 1 and 5.

d) Molecules 3 and 4.

e) Molecules 1 and 4.

PRACTICE: The ___/___ configuration of a monosaccharide is determined by the ________________ of the chiral carbon

furthest from the carbonyl group, while the ___/___ anomers are determined by _______________ of the anomeric carbon.

a) D ; L ; conformations ; R ; S ; configuration. d) D ; L ; configuration ; α ; β ; configuration.

b) R ; S ; conformation ; α ; β ; configuration. e) D ; L ; conformation ; α ; β ; conformation.

c) D ; L ; configuration ; α ; β ; conformation.



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CONCEPT: ANOMER

PRACTICE: Circle the and β anomers for the following D-monosaccharide:

PRACTICE: Answer the following questions regarding the following cyclic monosaccharide shown below:

A) Clearly label the hemiacetal carbon.

B) The monosaccharide is a(n) _________ anomer.

a) Alpha ().

b) Beta (β).

C) Draw the opposite anomer.

D) Draw the stereoisomer that differs in the arrangement of substituents at C2.



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CONCEPT: MUTAROTATION

Epimerization

●_______________________: process of interconverting epimers (changing one epimer into the other epimer).

□ Recall: epimers are diastereomers that differ ONLY in configuration of any one-__________ chiral carbon.

□ Requires a _____________ to break & reform the stable covalent bonds & change the ____________________.

Mutarotation

●_________________: a specific type of epimerization that interconverts _____________ (ex. converting α to β anomers).

□ Only _________ anomeric carbons forming a hemiacetal or hemiketal mutarotate.

●Mutarotation breaks/reforms bonds; HOWEVER, since hemiacetals/hemiketals are unstable, ______ catalyst is needed.

□ One ring anomer briefly opens up to the linear chain, then closes again to produce opposite ring anomer.

PRACTICE: The transformation of a monosaccharide to its ______________ occurs easily and does not require a catalyst.

a) Epimer. b) Anomer. c) Diastereomer. d) Enantiomer.

PRACTICE: Which of the following sugars undergoes mutarotation in neutral aqueous solution?

a) I and III.

b) III and IV.

c) II, III and IV.

d) I and IV.

e) I, II and IV.



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Chair Chair

Boat

CONCEPT: PYRANOSE CONFORMATIONS

●Cyclic monosaccharides can exist in a variety of __________________ (potentially flexible 3D arrangements).

□ Recall: unlike configurations, conformations CAN change _____________ breaking/reforming bonds.

Pyranose Conformations

●Pyranose conformations include __________ & _________ conformations (just like cyclohexane).

□ Substituents can either occupy a more crowded __________ or a less crowded ________________ position.

□ Chair is _________ stable and thus predominates over the boat.

Chair Flip

●Recall: pyranose rings can assume ______ chair conformations.

●Chair _________: process of converting one chair conformation to another.

□ Substituents change their _______/_____________ positions, but up/downwards positions are ______________.

□ Equatorial Preference: most stable conformation has bulky groups in less crowded ________________ positions.



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CONCEPT: PYRANOSE CONFORMATIONS

PRACTICE: Circle the TWO chair conformations that could apply upon cyclization of the following linear monosaccharide:

β-Anomer of Glucose Predominates

●Glucose exists predominantly in its cyclic _____-D-glucopyranose anomer.

□ Glucose composition: ~64% ____ anomer, ~35% ____ anomer, & >1% linear chain.

□ Glucose β anomer is most stable due to _________________ preference.

□ NOTE: chair-flip ≠ mutarotation.



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CONCEPT: COMMON MONOSACCHARIDES

●Some of the most common aldose and ketose monosaccharides in nature are shown below:



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Monosaccharide Structures Worth Memorizing

●The monosaccharide structures worth memorizing will vary from course to course, but here are a few common ones!

Cyclic Forms of Monosaccharides

●We can use the linear forms of sugars to derive their __________ forms:

□ β-D-Glucopyranose. □ α-D-Mannopyranose. □ α-D-Galactopyranose. □ α-D-Fructofuranose.

□ α-D-Ribofuranose. □ α-D-Deoxyribofuranose.

PRACTICE: Which of the following pairs of sugars are epimers of each other?

a) D-fructose and L-fructose. c) D-ribose and D-deoxyribose.

b) D-mannose and D-glucose. d) D-galactose and D-fructose.



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PRACTICE: The sugar α-D-Mannose is a sweet-tasting sugar. β-D-Mannose, on the other hand, tastes bitter. A pure

solution of α-D-mannose loses its sweet taste with time as it is converted into the β anomer. Draw the β anomer:

PRACTICE: Draw the α-furanose and β-pyranose forms of D-ribose.

PRACTICE: Indicate if the following pairs of sugars are enantiomers, anomers, epimers, or an aldose-ketose pair:

a) α-D-galactopyranose and β-D-galactopyranose. ____________________

b) D-glucose and D-mannose. ____________________

c) D-glucose and D-fructose. ____________________

d) α-D-glucopyranose and β-D-glucopyranose. ____________________

e) D-galactose and D-glucose. ____________________

f) α-D-mannopyranose and α-L-mannopyranose. ____________________



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Sugar Phosphates, Sugar acids (Aldonic,

Uronic, & Sialic acids), Sugar alcohols

(Alditols), Deoxy Sugars, Amino Sugars

DNA

CONCEPT: DERIVATIVES OF MONOSACCHARIDES

●Recall: In addition to simple sugars with formula Cn(H2O)n, there are also many ___________ sugars in nature.

●Monosaccharide Derivatives (or complex monosaccharides): chemically _________________ monosaccharides.

□ Hydroxyl groups (-OH) _______________ with other chemical groups.

●_____ major groups of monosaccharide derivatives:

1) Sugar Phosphates

●Sugar Phosphates: carbohydrates that are covalently attached to _______________ groups.

□ Part of the structure of _______________________ that make up nucleic acids (ex. DNA).

□ Important intermediates in the pathways of carbohydrate ________________ & catabolism.



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2) Sugar Alcohols (Alditols)

●Sugar Alcohols: sugars whose carbonyl group is reduced to an __________ (-OH) group so that every carbon has a -OH.

□ Usually has the suffix “-________.”

EXAMPLE: Sugar Alcohols.

PRACTICE: What is the name of the sugar alcohol produced when D-ribose is reduced?

a) L-ribose. b) D-ribitol. c) D-ribulose. d) L-ribitol. e) L-ribulose.

3) Deoxy Sugars

●Deoxy Sugars: sugars ____________ at least one ___________ group, usually due to replacement with hydrogen atoms.

□ 2-__________-D-ribose is a primary building block of DNA in all organisms.

EXAMPLE: Deoxy Sugars in DNA.

4) Amino Sugars

●Amino Sugars: sugars containing an ____________ group instead of a hydroxyl group.

□ Commonly found in many oligo & polysaccharides (ex. chitin) and usually have the suffix “-_________.”

EXAMPLE: Amino Sugars.



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PRACTICE: What is the difference between deoxyribose and ribose?

a) Deoxyribose is a D form, whereas ribose is an L form.

b) Deoxyribose has one less oxygen atom than ribose.

c) Ribose is found in the straight chain structure, whereas deoxyribose is not.

d) Ribose is a monosaccharide, but deoxyribose is a polysaccharide.

e) All statements are incorrect.

5) Sugar Acids

●Sugar Acids: carbohydrates with ________________ acids.

□ _____ main types of sugar acids: 1) ___________ Acids. 2) ___________ Acids. 3) ___________ Acids.

1) Aldonic Acids: aldoses whose C1 ______________ group is oxidized to a carboxylic acid (usually has suffix “-_______”).

2) Uronic Acids: sugars whose _______________-numbered carbon is oxidized to a carboxylic acid.

□ Usually has suffix “-________.”

3) Aldaric Acids: sugars whose ______________ & _______________-numbered carbons are oxidized to carboxylic acids.

□ Usually has suffix “-________.”

EXAMPLE: Label the following sugar acids:

PRACTICE: Classify the following sugar acids as aldonic, uronic or aldaric acids:



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CONCEPT: REDUCING SUGARS

●Hemiacetals & hemiketals are susceptible to reacting with alcohols to form more stable _________ & _________ groups.

Reducing Sugars vs. Non-Reducing Sugars

●Note: Aldoses & ketoses can reversibly rearrange into each other via the Enediol Rearrangement mechanism.

●Reducing Sugars: any sugar capable of being oxidized (by acting as a _______________ agent).

□ Must either have or can rearrange to generate a free ________________ group.

1) Includes ALL simple, ___________ sugars.

2) Includes cyclic sugars with a _________ hemiacetal or hemiketal (which are in with their linear forms).

●_______-Reducing Sugars: __________________ of a reducing sugar; includes ____________ & ____________.

EXAMPLE: Appropriately label each of the following carbohydrates as reducing sugars or non-reducing sugars.

PRACTICE: Which chemical modification (I-IV) converts D-fructofuranose from a reducing to a non-reducing carbohydrate?

a) I.

b) II.

c) III.

d) IV.

e) None of them.



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CONCEPT: REDUCING SUGARS

PRACTICE: Which of the following disaccharides are reducing sugars?

a) Sugars A & B. b) Sugars B & C. c) Sugars C & D. d) Sugars A & C. e) >2 sugars.

PRACTICE: Which chemical group below indicates that the sugar is a reducing disaccharide? Is “C” an acetal or ketal?

a) A. b) B. c) C. d) D. e) E.

PRACTICE: Which of the molecules below have a reducing end?

a) Molecule 1.

b) Molecule 2.

c) Molecule 3.

d) Both Molecules 2 and 3.

e) Molecules 1, 2, and 3.



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CONCEPT: REDUCING SUGARS TESTS

Fehling’s Test for Reducing Sugars

●_____________ Test: an experimental color-change reaction that tests for the presence of ________________ sugars.

□ Blue Cu2+ + ______-Reducing Sugar = Blue Cu2+. □ Blue Cu2+ + Reducing Sugar = _______ Cu2O.

Benedict’s Test for Reducing Sugars

●The Benedict’s test is very ______________ to the Fehling’s test in terms of reaction & overall test result.

□ Benedict’s solution uses slightly different reagents giving it a longer shelf-life, otherwise, Fehling’s ≈ Benedict’s.

Tollens’ Test for Reducing Sugars

●Tollen’s test uses silver (_____) as the oxidizing agent instead of Cu2+, but still tests for presence of reducing sugars.



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CONCEPT: REDUCING SUGARS TESTS

PRACTICE: Which of the following would you predict to be the LEAST reactive in a Fehling's test for reducing sugars?

a) D-Glucose. b) L-Glucose. c) D-Mannose. d) D-Ribose. e) D-Fructose.

PRACTICE: Which of these statements is false?

a) The Fehling’s test allows us to detect the presence of reducing sugars.

b) The Benedict’s test allows us to detect the presence of sugars with a free aldehyde or ketone group.

c) All simple, linear monosaccharides are reducing sugars.

d) All disaccharides have exposed carbonyl groups and are also reducing sugars.

e) Sucrose and other non-reducing sugars will not react with Tollens’ solution.

PRACTICE: Select the incorrect statement below:

a) Sugars that contain aldehyde groups that are oxidized to carboxylic acids are classified as reducing sugars.

b) Reducing sugars reduce the Cu2+ in Benedict's solution to Cu+ which then forms a red precipitate, copper (I) oxide.

c) Any monosaccharide that contains a free hemi-acetal will be a reducing sugar.

d) Glycosides have acetals and therefore are reducing sugars.

e) Acetals of monosaccharides can’t undergo mutarotation or oxidation, meaning that acetals are nonreducing.

f) Fructose (though a ketose) is also a reducing sugar because in the open-chain form, a rearrangement between the

hydroxyl group on C1 and the ketone group on C2 provides an aldehyde group that can be oxidized.

PRACTICE: In the table below, indicate what the result of a Fehling’s, Benedict’s, and Tollen’s test would be for each of the

two sugars and what conclusion can be made about the properties of the sugars.



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CONCEPT: GLYCOSIDIC BOND

●______________ bond: an acetal or ketal linkage between a sugar’s anomeric carbon & another chemical group.

□ Form via ________________ synthesis reactions.

□ ______________: compounds containing glycosidic bonds.

PRACTICE: The molecular formula of glucose is C6H12O6. What is the molecular formula for an oligosaccharide made by

linking 10 glucose molecules together by dehydration synthesis? (Hint: Consider how many glycosidic bonds form).

a) C60H120O60. b) (C6H12O6)10. c) C60H102O51. d) C60H100O50.

O-Glycosidic Bonds & N-Glycosidic Bonds

●Among the many types of glycosidic bonds, there are ______ primary types:

1) _____-Glycosidic Bond: a glycosidic bond between an anomeric carbon & an _____________ atom.

2) _____-Glycosidic Bond: a glycosidic bond between an anomeric carbon & a ______________ atom.



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Naming Glycosidic Bonds

●Glycosidic bonds are named based on _______ criteria:

1) ___________________ of anomeric carbon(s) involved in the glycosidic linkage (either or β).

2) __________________ of carbon atoms involved in the glycosidic linkage.

●Single-headed ( ) & double-headed arrows ( ) respectively suggest ___ & ___ anomeric carbon(s) involved in bond.

□ Commas can also be used to replace arrows.

EXAMPLE: Name the following glycosidic bonds:

PRACTICE: What is the name for the glycosidic linkage in the following glycoside?

a) 1, 1 glycosidic linkage. c) 1, 4 glycosidic linkage.

b) 1, 2 glycosidic linkage. d) 1, 6 glycosidic linkage.

PRACTICE: Determine the name of the glycosidic bond of the following disaccharide.

a) -1,2-glycosidic bond. d) β-1,4-glycosidic bond.

b) β-1,3-glycosidic bond. e) β-1,3-glycosidic bond.

c) -1,4-glycosidic bond.



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PRACTICE: Which two molecules below do NOT contain a 1,4 glycosidic linkage?

a) A & B.

b) B & C.

c) C & A.

d) D & C.

e) E & D.

PRACTICE: Label & name every glycosidic bond in the branched oligosaccharide below:

PRACTICE: Raffinose is the most abundant trisaccharide in nature. Answer the questions based on its provided structure:

A) Is Raffinose a reducing or a non-reducing sugar? ______________________.

B) Identify the 3 monosaccharides that compose raffinose:

1) ______________________. 2) ______________________. 3) ______________________.

C) Name the TWO glycosidic linkages that connect the sugars in raffinose:

1) ______________________. 2) ______________________.



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CONCEPT: DISACCHARIDES

●________________________: consists of _______ monosaccharides covalently linked by an O-glycosidic bond.

●Many disaccharides exist, but the most ________________ ones are maltose, cellobiose, lactose & sucrose.

PRACTICE: Which of the following contains galactose as one of the sugar subunits?

a) Glucose. b) Ribose. c) Maltose. d) Lactose. e) Cellobiose.

PRACTICE: Which disaccharide forms a 1,1-glycosidic linkage?

a) Lactose. c) Maltose.

b) Trehalose. d) Sucrose.

PRACTICE: What is the identity of the disaccharide below?

a) Cellulose. e) Sucrose.

b) Lactose. f) Lactose.

c) Chitin. g) Cellobiose.

d) Maltose. h) Glycogen.

Milk



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A B

CONCEPT: DISACCHARIDES

PRACTICE: The structure of a disaccharide is shown below. Which statement applies?

a) Both sugar rings A and B are in equilibrium with their linear chain forms.

b) Only sugar ring A is in equilibrium with its linear chain form.

c) Only sugar ring B is in equilibrium with its linear chain form.

d) Neither sugar ring is in equilibrium with their linear chain form.

e) None of the above statements are correct.

PRACTICE: Name each monosaccharide unit & the glycosidic linkage in the following disaccharide (gentiobiulose).

PRACTICE: Given the following information, draw a Haworth projection for the disaccharide gentibiose:

1. Gentibiose is a dimer of glucopyranoses.

2. The glycosidic linkage is β(1 → 6).

3. The anomeric carbon not involved in the glycosidic linkage is in the α configuration.



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CONCEPT: GLYCOCONJUGATES

●__________________________: oligosaccharides conjugated to another chemical species (ex. lipids or proteins).

□ Oligosaccharide portions of glycoconjugates are usually very __________________.

□ Can show ____________________ with a non-reducing-end & a reducing-end.

Glycolipids

●________________: a hybrid molecule made of a ____________ covalently linked to relatively small sugars.

Glycoproteins

●Glycoproteins: a hybrid molecule made of mostly ____________ covalently linked to relatively small _________________.

□ Found inside cells, in the extracellular matrix, & on the outer surface of plasma membranes.

□ ________________ are glycoproteins.



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CONCEPT: GLYCOCONJUGATES

O-Linked vs. N-Linked Glycoproteins

●Glycoproteins form glycosidic bonds between a sugar’s ______________ carbon & an amino acid residue’s ____-group.

1) ____-linked glycosidic linkage: forms with -OH of _______ or _______ residues.

2) ____-linked glycosidic linkage: forms with amide nitrogen of an _______ residue.

PRACTICE: In glycoproteins, the carbohydrate moiety is always attached through the amino acid residues:

a) Asparagine, Serine, or Threonine. d) Glycine, Alanine, or Aspartate.

b) Aspartate or Glutamate. e) Tryptophan, Aspartate, or Cysteine.

c) Glutamine or Arginine.

PRACTICE: The O-linked glycoproteins of eukaryotes usually have their sugar chains attached to:

a) Buried carbonyls in the protein backbone. d) The carboxyl terminal residue.

b) Surface carbonyls in the protein backbone. e) The carboxyl groups of Asp or Glu.

c) The OH of Ser or Thr residues.



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CONCEPT: POLYSACCHARIDE

●Polysaccharides can be ENORMOUS (>1 million units), but other than that, their composition is relatively __________.

□ Usually consist of just _____ or _____ monosaccharides repetitively linked together.

□ Functions include ______________ Support or _____________-Storage. .

How Do Polysaccharides Differ from Each Other?

●Polysaccharides differ from each other in at least one of the following _____ ways:

1) ____________ of their reoccurring sugar units. 3) ___________ of chain (total # of sugar units).

2) Types of _____________ bonds linking their sugar units. 4) Degree of _________________.

●Each of these 4 factors influences a polysaccharide’s _______________ & _______________ properties.

Homopolysaccharides vs. Heteropolysaccharides

●______ major categories of polysaccharides:

1) __________polysaccharides: consist of repeating units of only ______ single type of monosaccharide.

□ Usual functions: _______cellular structures & energy-______________.

2) ____________polysaccharides: consist of ______ 2 different kinds of monosaccharides.

□ Usual functions: _______cellular structures.



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CONCEPT: CELLULOSE

□ Cellulose: indigestible to most animals due to lack of ______________ enzyme that hydrolyzes (β1 4) linkages.

PRACTICE: Which statement about cellulose is true?

a) It’s a highly branched polysaccharide. d) Its D-fructose residues have configuration.

b) It’s the main storage polysaccharide in some strains of dogs. e) It’s a homopolysaccharide of D-glucoses.

c) It cannot be digested by any animal.

PRACTICE: Cellulose is composed of which of the following monosaccharides covalently bonded together in a long chain?

a) -glucose. c) β-glucose. e) Peptidoglycan.

b) Amino acids. d) Cellobiose. f) Chitin.

PRACTICE: Cellulose fibers most closely resemble _____________ in proteins.

a) -helices. b) β-sheets c) β-turns. d) Coiled-coils.

Plant

Plant Cells Plant Cell Wall

Cellulose

_____________



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https://en.wikipedia.org/wiki/Plastid

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https://creativecommons.org/licenses/by-sa/3.0/

CONCEPT: CHITIN

□ N-acetylglucosamine = _________

PRACTICE: Chitin is:

a) A branched homopolysaccharide of N-acetylglucosamine.

b) A heteropolysaccharide of N-acetylglucosamine and N-acetylmuramic acid.

c) An unbranched complex heteropolymer of many sugars.

d) An unbranched homopolysaccharide of N-acetylglucosamine.

PRACTICE: Indicate whether or not each of the following characterizations applies to the following:

(1) Chitin only, (2) Cellulose only, (3) Both Cellulose and Chitin, (4) Neither.

a) Structural polysaccharide: ____________.

b) Monomers are glucose amino sugar derivatives: ____________.

c) Glycosidic linkages are all (β-1,4): ____________.

d) Homopolysaccharide: ____________.

PRACTICE: Which of the following statements best describes the main structural difference between cellulose and chitin?

a) Chitin contains -1,4-glycosidic linkages while cellulose contains β-1,4-glycosidic linkages.

b) The C-2 carbon in the cellulose monomer contains an N-acetylamino group instead of an -OH group.

c) Cellulose is a linear, unbranched homopolysaccharide while chitin is a branched homopolysaccharide.

d) The C-2 carbon in the chitin monomer contains an N-acetylamino group instead of an -OH group.



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CONCEPT: PEPTIDOGLYCAN

□ N-acetylglucosamine (_______). □ N-acetylmuramic acid (_______).

□ Short ____________ cross-links these polysaccharides (thus the “peptido-” prefix).

Gram-Positive vs. Gram-Negative Bacteria

●Bacteria are categorized based on whether or not they absorb the _________ Stain.

□ Gram-positive bacteria __________ the stain; HOWEVER, gram-negative bacteria do _______ absorb the stain.

●Gram-___________ bacteria: cell membrane surrounded by just a ________ cell wall (~250 Å).

●Gram-___________ bacteria: cell membrane surrounded by _______ cell wall (~30 Å) & a complex ________ membrane.

□ Outer membrane makes gram-negative bacteria more ______________ to some antibiotics.



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CONCEPT: PEPTIDOGLYCAN

PRACTICE: What type of molecule provides the “cross-links” between the peptidoglycan polysaccharides?

a) Fatty acid. c) Carbohydrate. e) Salt bridge.

b) Lipid. d) Protein.

PRACTICE: Which of the following best describes the structure of the Gram-negative cell wall?

a) A thin layer of chitin with an outer membrane on top.

b) A thin peptidoglycan layer between two cell membranes.

c) A thick peptidoglycan layer with an outer membrane on top.

d) A thick peptidoglycan later under an outer membrane.



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CONCEPT: STARCH

Starch: Amylose & Amylopectin

Amylose is an Unbranched Form of Starch

Amylopectin is a Branching Form of Amylose

●Amylopectin branchpoints occur every 24-30 residues via (α1 ____) glycosidic linkages.

_________



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CONCEPT: STARCH

PRACTICE: Which of the following is a structural polysaccharide in plant cells?

a) Glycogen. c) Chitin. e) Cellulose.

b) Amylose. d) Starch.

PRACTICE: Cellulose fibers resemble ___________ in proteins; whereas amylose’s structure is similar to _____________.

a) -helices; β-sheets. d) -helices; β-turns.

b) β-sheets; -helices. e) β-turns; coiled-coils.

c) β-sheets; the hydrophobic core.

PRACTICE: Cellulose, an unbranched β(1-4)-linked homopolysaccharide of D-glucose, differs from starch in that starch is:

a) A β-1,6-linked D-mannose homopolysaccharide that is branched.

b) A β-1,6-linked D-glucose homopolysaccharide that is unbranched.

c) An -1,6-linked D-glucose homopolysaccharide that can be branched or unbranched.

d) An -1,4-linked D-glucose homopolysaccharide that can be branched or unbranched.

e) An -1,4-linked D-mannose homopolysaccharide that is branched.



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CONCEPT: GLYCOGEN

Glycogen is Amylopectin with More Branching

□ Glycogen branchpoints occur more frequently, every 8-12 residues, via (α1 ____) glycosidic linkages.

PRACTICE: The storage form of carbohydrates in animals is:

a) Glucose. b) Amylopectin. c) Lactose. d) Glycogen.

PRACTICE: In glycogen there are:

a) Alpha 1-4 glycosidic bonds only. d) Alpha 1-4 and 1-6 glycosidic bonds only.

b) Alpha 1-5 glycosidic bonds only. e) Alpha 1-4 and beta 1-4 glycosidic bonds.

c) Alpha 1-6 glycosidic bonds only.

____________ ____________



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CONCEPT: GLYCOGEN

Polysaccharide Review

●Let’s review the polysaccharides we’ve covered so far:



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CONCEPT: LECTINS

Sugar Code

●Sugar Code: cells can use carbohydrates to ___________ biological information leading to different events.

□ Sugar Code “Letters” = ________saccharides. □ Sugar Code “_________” = Oligosaccharides.

Lectins “Translate” the Sugar Code

●_____________: proteins that ________ carbohydrates (in order to perform many biological functions).

□ Lectin-carbohydrate interactions are _______-covalent & reversible (just like protein-ligand interactions).

PRACTICE: The biochemical property of lectins that is the basis for most of their biological effects is their ability to bind to:

a) Amphipathic molecules. d) Specific lipids. e) Specific peptides.

b) Hydrophobic molecules. e) Specific oligosaccharides. f) Specific monosaccharides.

PRACTICE: Lectins are _________________________ while glycoproteins are _________________________.

a) Lipids ; neurotransmitters.

b) Proteins that covalently bind to specific sugars ; proteins that are non-covalently bound to sugar residues.

c) Storage carbohydrates ; enzyme specific hydrolysis of storage carbohydrates.

d) Structural carbohydrates ; enzymes specific for hydrolysis of structural carbohydrates.

e) Proteins that noncovalently bind to specific sugars ; proteins that are covalently bound to sugar residues



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CONCEPT: LECTINS

Integrins & Selectins

●______________: plasma-membrane-lectins mediating signals between a cell & the _____________________ matrix.

□ Extracellular Matrix (ECM): network of molecules ___________ cells that provide structural/biochemical support.

●______________: plasma-membrane-lectins mediating cell-_______ recognition & adhesion.

PRACTICE: Which of the following statements regarding integrins is FALSE?

a) Integrins have quaternary protein structure.

b) Integrins are transmembrane protein but most of their functional parts are extracellular.

c) Integrins form tight junctions between cells.

d) The same integrins can have different affinities to ligands depending upon its conformation.

PRACTICE: Which of the following types of interactions is not used by lectins to recognize specific glycans?

a) Hydrogen bonds.

b) Salt bridges.

c) Van der Waals contacts.

d) Disulfide bonds.



Page 49

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