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Angelie 11/14 > Summarize Content - Upload File > Flashcards

Summarize Content - Upload File Flashcards

1
Q

What are osides?

A

Complex carbohydrates divided into two classes: holosides and heterosides

Holosides are formed by the association of sugar molecules, while heterosides (glycoconjugates) are formed by the association of sugars with non-carbohydrate molecules.

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2
Q

What are holosides?

A

Polymers formed exclusively of sugars or sugar derivatives linked by O-glycosidic bonds

Holosides consist of residues of sugars linked together, forming complex carbohydrates.

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3
Q

What are heterosides?

A

Glycoconjugates formed by the association of one or more sugars with a non-carbohydrate molecule

Heterosides include various types of molecules beyond just sugars.

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4
Q

Define glycosidic bond.

A

Covalent bond formed between the anomeric carbon of a sugar and a hydroxyl, amine, or thiol group of another molecule

Glycosidic bonds can be O-glycosidic, N-glycosidic, or S-glycosidic, depending on the type of group involved.

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5
Q

What happens to mutarotation when a glycosidic bond is formed?

A

Mutarotation ceases because the anomeric carbon’s configuration becomes fixed

The fixed configuration is used to define the type of glycosidic bond.

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6
Q

What is the difference between α and β glycosidic bonds?

A

α glycosidic bond has the anomeric carbon in the α position, while β glycosidic bond has it in the β position

This distinction affects the structure and properties of the resulting carbohydrate.

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7
Q

What are disaccharides?

A

Carbohydrates formed from 2 sugar residues linked by a glycosidic bond

Disaccharides include maltose, cellobiose, lactose, and sucrose.

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8
Q

How are oligosaccharides defined?

A

Carbohydrates composed of 3 to 20 sugar residues

Oligosaccharides can be linear or branched and are often linked to lipids or proteins.

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9
Q

What are polysaccharides?

A

Carbohydrates composed of more than 20 sugar residues

Polysaccharides can be homopolysaccharides or heteropolysaccharides.

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10
Q

What are reducing sugars?

A

Simple cyclic sugars that can reduce an oxidizing agent due to their free anomeric carbon

Examples of reducing sugars include maltose, cellobiose, and lactose.

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11
Q

What is a non-reducing sugar?

A

Sugar with no free anomeric carbon, involved in glycosidic bonds

Sucrose is an example of a non-reducing sugar.

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12
Q

What is the structure of α-amylose?

A

Linear polymer of glucose units linked by α(1→4) glycosidic bonds

α-amylose is slightly soluble in water and forms a helical structure.

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13
Q

What is glycogen?

A

Homopolymer of glucose that serves as a storage polysaccharide in animals

Glycogen has more branching than amylopectin, with branches occurring every 8 to 12 glucose residues.

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14
Q

What distinguishes cellulose?

A

Linear polymer of glucose linked by β(1→4) glycosidic bonds

Cellulose forms strong fibers due to hydrogen bonding between chains, making it insoluble in water.

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15
Q

Fill in the blank: The main component of the cell walls in plants is _______.

A

Cellulose

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16
Q

What is the function of starch in plants?

A

Storage polysaccharide composed of amylose and amylopectin

Starch is the most important carbohydrate in human nutrition.

17
Q

True or False: All polysaccharides are linear.

A

False

Polysaccharides can be either linear or branched.

18
Q

What are glycoproteins?

A

Proteins that have oligosaccharides covalently attached

Glycoproteins serve various functions, including cell recognition and signaling.

19
Q

What is raffinose?

A

A trisaccharide found in vegetables, not digested by humans

Raffinose can be fermented by bacteria in the intestine, producing gas.

20
Q

What type of linkage is found in cellulose?

A

β(1→4) glycosidic linkages

Cellulose has straight chains that can form hydrogen bonds, providing mechanical strength.

21
Q

What is the structural role of cellulose in plants?

A

It allows plants to grow up to 30 meters to seek light

Cellulose’s mechanical strength is crucial for the structural integrity of plants.

22
Q

What is chitin and where is it found?

A

The main structural component of insect and crustacean exoskeletons

Chitin is also present in the cell walls of some fungi, algae, and yeasts.

23
Q

What is the structural composition of chitin?

A

Linear polymer of N-acetyl-D-glucosamine residues linked by β(1→4) bonds

Chitin structurally resembles cellulose and exists in microfibrils.

24
Q

Define heterosides.

A

Molecules formed by the association of sugars and non-carbohydrate substances called aglycones

Aglycones can include phenolic compounds, alkaloids, steroids, lipids, and proteins.

25
Q

What are the two criteria for classifying glycoconjugates?

A
  1. Nature of aglycone
  2. Type of linkage (N-glycosidic, O-glycosidic, S-glycosidic)

Glycoconjugates can be glycolipids or glycoproteins based on the aglycone type.

26
Q

What is peptidoglycan?

A

A compound composed of heteropolysaccharides linked to peptides in bacterial cell walls

Contains repeated units of N-acetylglucosamine and N-acetylmuramic acid.

27
Q

What are glycosaminoglycans (GAGs)?

A

Polymers formed by repeating disaccharide units of an amino sugar and uronic acid

GAGs can have over 25,000 repeats and are negatively charged due to sulfate and carboxyl groups.

28
Q

What is the significance of sulfate and carboxyl groups in GAGs?

A

They confer a strong negative charge to GAGs

This charge is important for their biological functions and interactions.

29
Q

True or False: Polysaccharides have a well-defined molecular mass.

A

False

Polysaccharides exhibit microheterogeneity, meaning they can vary in size and composition within the same cell.

30
Q

What is the first step in analyzing a glycoconjugate?

A

Release the aglycone part using enzymes like glycosidases

This is essential for further purification and analysis of the polysaccharide.

31
Q

What methods can be used for the purification of polysaccharides?

A
  1. Precipitation
  2. Centrifugation
  3. Chromatography (exclusion, ion exchange, affinity)

Affinity chromatography is particularly effective for sugars using lectins as ligands.

32
Q

How can the composition of a carbohydrate be determined?

A

By hydrolyzing the glycosidic bond and identifying residues using HPLC or gas chromatography

This allows for detailed analysis of the sugar components.

33
Q

What advanced techniques are used to determine the composition and sequence of glycosidic residues?

A

Mass spectrometry (MS) and nuclear magnetic resonance (NMR)

These techniques provide detailed structural information about carbohydrates.

Angelie 11/14 (2 decks)

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