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Question 1

What are osides?

Answer 1

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.

Question 2

What are holosides?

Answer 2

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

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

Question 3

What are heterosides?

Answer 3

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

Heterosides include various types of molecules beyond just sugars.

Question 4

Define glycosidic bond.

Answer 4

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.

Question 5

What happens to mutarotation when a glycosidic bond is formed?

Answer 5

Mutarotation ceases because the anomeric carbon’s configuration becomes fixed

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

Question 6

What is the difference between α and β glycosidic bonds?

Answer 6

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.

Question 7

What are disaccharides?

Answer 7

Carbohydrates formed from 2 sugar residues linked by a glycosidic bond

Disaccharides include maltose, cellobiose, lactose, and sucrose.

Question 8

How are oligosaccharides defined?

Answer 8

Carbohydrates composed of 3 to 20 sugar residues

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

Question 9

What are polysaccharides?

Answer 9

Carbohydrates composed of more than 20 sugar residues

Polysaccharides can be homopolysaccharides or heteropolysaccharides.

Question 10

What are reducing sugars?

Answer 10

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

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

Question 11

What is a non-reducing sugar?

Answer 11

Sugar with no free anomeric carbon, involved in glycosidic bonds

Sucrose is an example of a non-reducing sugar.

Question 12

What is the structure of α-amylose?

Answer 12

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

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

Question 13

What is glycogen?

Answer 13

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.

Question 14

What distinguishes cellulose?

Answer 14

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.

Question 15

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

Answer 15

Cellulose

Question 16

What is the function of starch in plants?

Answer 16

Storage polysaccharide composed of amylose and amylopectin

Starch is the most important carbohydrate in human nutrition.

Question 17

True or False: All polysaccharides are linear.

Answer 17

False

Polysaccharides can be either linear or branched.

Question 18

What are glycoproteins?

Answer 18

Proteins that have oligosaccharides covalently attached

Glycoproteins serve various functions, including cell recognition and signaling.

Question 19

What is raffinose?

Answer 19

A trisaccharide found in vegetables, not digested by humans

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

Question 20

What type of linkage is found in cellulose?

Answer 20

β(1→4) glycosidic linkages

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

Question 21

What is the structural role of cellulose in plants?

Answer 21

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

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

Question 22

What is chitin and where is it found?

Answer 22

The main structural component of insect and crustacean exoskeletons

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

Question 23

What is the structural composition of chitin?

Answer 23

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

Chitin structurally resembles cellulose and exists in microfibrils.

Question 24

Define heterosides.

Answer 24

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

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

Question 25

What are the two criteria for classifying glycoconjugates?

Answer 25

1. Nature of aglycone 2. Type of linkage (N-glycosidic, O-glycosidic, S-glycosidic) ## Footnote Glycoconjugates can be glycolipids or glycoproteins based on the aglycone type.

Question 26

What is peptidoglycan?

Answer 26

A compound composed of heteropolysaccharides linked to peptides in bacterial cell walls ## Footnote Contains repeated units of N-acetylglucosamine and N-acetylmuramic acid.

Question 27

What are glycosaminoglycans (GAGs)?

Answer 27

Polymers formed by repeating disaccharide units of an amino sugar and uronic acid ## Footnote GAGs can have over 25,000 repeats and are negatively charged due to sulfate and carboxyl groups.

Question 28

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

Answer 28

They confer a strong negative charge to GAGs ## Footnote This charge is important for their biological functions and interactions.

Question 29

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

Answer 29

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

Question 30

What is the first step in analyzing a glycoconjugate?

Answer 30

Release the aglycone part using enzymes like glycosidases ## Footnote This is essential for further purification and analysis of the polysaccharide.

Question 31

What methods can be used for the purification of polysaccharides?

Answer 31

1. Precipitation 2. Centrifugation 3. Chromatography (exclusion, ion exchange, affinity) ## Footnote Affinity chromatography is particularly effective for sugars using lectins as ligands.

Question 32

How can the composition of a carbohydrate be determined?

Answer 32

By hydrolyzing the glycosidic bond and identifying residues using HPLC or gas chromatography ## Footnote This allows for detailed analysis of the sugar components.

Question 33

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

Answer 33

Mass spectrometry (MS) and nuclear magnetic resonance (NMR) ## Footnote These techniques provide detailed structural information about carbohydrates.