Lecture 6: Carbohydrates

Which monosaccharide is a major nutrient and central to cellular metabolism?

Glucose

Glycosidic linkage is a _______ bond that is used in joining disaccharides and polysaccharides by a ________ reaction.

Covalent, Dehydration

Which functional groups are a part of monosaccharide structure?

• Aldehyde

• Ketone

• Carbon chain

• Hydroxyl group

Define Triose.

Three carbon monosaccharide

Define Hexose.

Six carbon monosaccharide

Define Furan.

Five-member monosaccharide ring

Define Pentose.

Five carbon monosaccharide

Define Pyran.

Six-member monosaccharide ring

Define Tetrose.

Four carbon monosaccharide

Define Heptose.

Seven carbon monosaccharide

True/False: A disaccharide composed of glucose and fructose will always be sucrose.

False

Which polysaccharide characteristics can provide strength?

• Linear structure

• Bonds with Proteins

True/False: Proteoglycans contain more carbohydrate than protein.

True

Carbohydrate molecules are:

Hydrophilic

What is included in the structure of a Monosaccharide?

• Carbon chain 

• Hydroxyl groups (oxygen/hydrogen) 

• Aldehyde OR Ketone (oxygen) 

  • Monosaccharide w/ aldehyde = aldose 

  • Monosaccharide w/ ketone = ketose 

How are Monossacharides categorized?

• Categorized by their number of Carbons

• Typically have 3-7 carbons (3, 5, and 6 most common) 

  • Triose, tetrose, pentose, hexose, heptose (1-7 C) 

What are longer Monosaccharides able to form?

• Rings!!

• Longer monosaccharides are more stable as rings in solution 

  • Pentoses and hexoses are long enough to form furans and pyrans 

  • Tetroses and shorter monosaccharides are too short to form rings 

  • Hydroxyl group (3-4C away from =O) reacts with ketone/aldehyde 

    • No atoms are lost from the molecules in this process (just structural differences) 

What can Isomers in Monosaccharides impact?

Can alter both their metabolic fate and functional capacity.

How are Disaccharides formed?

• Form via diverse glycosidic linkages 

• Condensation reaction that forms a disaccharide 

  • Dehydration = water loss from one molecule 

  • Condensation = water loss from > one molecule 

• Disaccharides are name for: 

  • Monosaccharides involved 

  • Bond conformation 

What is a Glycosidic bond?

• Covalent bond formed between hydroxyl groups between to monosaccharides 

• Bond is named for the carbons connected 

  • Carbon 1 is the former ketone/aldehyde 

  • Count up from there 

How do structures of carbohydrates contribute to their functions?

• Modifications to carbohydrates alter their function 

  • Strength

  • Hydrophilicity

  • Specificity

Define Strength.

Addition of protein to carbohydrate provides structural cross-linking.

Define Hydrophilicity.

Addition of carbohydrates to protein and lipids provides higher interaction with water.

Define Specificity.

Carbohydrate monomers and polymers help molecules/cells identify each other.

How does the ration of protein to carbohydrate determine terminology?

• Protein > Carbohydrate = Glycoprotein 

• Carbohydrate > Protein = Proteoglycan 

What role do Carbohydrates play in Antibodies?

Carbohydrates on heavy chain facilitate immune cell recognition 

What role do Carbohydrates play in Peptidoglycan?

Cross-linkages between chains provide strength to bacterial cell walls

What role do Carbohydrates play in Aggrecan?

Large carbohydrate moieties become hydrated to provide cartilage with resistance 

What is a Glycolipid?

• Lipid with carbohydrate bound to an alcohol group (amphipathic) 

• Extremely structurally diverse 

  • Provide tissue, organ, and organismal specificity “markers” 

  • Allow interaction with hydrophilic molecules 

    
    

What is a Polysaccharide?

Long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. 

What function do Polysaccharides play in cell functions?

• Energy storage and liberation 

  • Polymers that can easily be broken down into monomers that enter metabolic pathways 

• Structure 

  • Keep cells, tissues, and whole organisms in shape 

How is Polysaccharide function related to its structure?

• Polysaccharide structure is linked to function 

• Branching is an indication of metabolism 

  • Structural polysaccharides are more linear 

    • Strong shape, packs together easily 

  • Energy storage polysaccharides are highly branched 

    • Many ends for enzymes to work on 

• Variability in polysaccharide structure influences digestion