Lecture 10 Carbohydrates

Q: What is the basic formula for carbohydrates?

A: (CH₂O)n

Q: What are the two main types of monosaccharides based on their functional groups?

A: Aldoses (aldehyde group) and Ketoses (ketone group)

Q: What is the primary energy source for cells in monosaccharides?

A: Glucose

Q: What type of bond forms between two monosaccharides?

A: Glycosidic bond

Q: What is the difference between α and β stereoisomers in carbohydrates?

A: In α-form, the –OH group is opposite the –CH₂OH group; in β-form, they are on the same side.

Q: What are the two types of stereoisomers in carbohydrates?

A: D-isomers and L-isomers

Q: What are the building blocks of polysaccharides?

A: Monosaccharides

Q: What is a reducing sugar?

A: A sugar that can act as a reducing agent, such as lactose, which has a free anomeric carbon.

Q: What is the main storage polysaccharide in plants?

A: Starch

Q: What is the primary storage polysaccharide in animals?

A: Glycogen

Q: What are glycosaminoglycans (GAGs)?

A: Heteropolysaccharides in the extracellular matrix that provide structure and absorb shock.

Q: What is the function of proteoglycans?

A: Macromolecules of the ECM that help with tissue structure and cellular signaling.

Q: What is the function of glycoproteins?

A: Proteins with oligosaccharides attached, involved in processes like cell signaling.

Q: What type of glycosidic bond is found in amylose?

A: α1→4 glycosidic bond

Q: What is the structural difference between amylose and amylopectin?

A: Amylose is unbranched, while amylopectin is branched with α1→6 linkages.

Q: How do animals store carbohydrates?

A: In the form of glycogen, which is highly branched.

Q: What is cellulose composed of?

A: β1→4 glycosidic linkages of glucose residues

Q: Why can humans not digest cellulose?

A: Humans lack the enzyme to hydrolyze β1→4 glycosidic bonds.

Q: What is chitin, and where is it found?

A: A structural polysaccharide found in the exoskeletons of insects and crustaceans.

Q: What is the function of glycoproteins in blood?

A: They are involved in immune responses, such as antibodies.

Q: What determines blood types (A, B, AB, O)?

A: Specific carbohydrate antigens on the surface of red blood cells.

Q: What are lectins?

A: Proteins that bind specific sugars and mediate biological processes.

Q: What role do lectins play in blood typing?

A: Lectins bind to specific carbohydrate antigens on red blood cells to identify blood types.

Q: What are selectins?

A: A family of lectins that mediate cell-cell recognition and inflammation.

Q: What is the role of the extracellular matrix (ECM)?

A: It provides structural support and pathways for nutrient and oxygen diffusion in tissues.

Q: What is a glycosidic bond?

A: A covalent bond that links carbohydrate molecules to each other or to other molecules.

Q: What is the difference between homopolysaccharides and heteropolysaccharides?

A: Homopolysaccharides contain only one type of monomer, while heteropolysaccharides contain two or more kinds.

Q: How are polysaccharides like starch and glycogen stored in the body?

A: In hydrated form, with exposed hydroxyl groups hydrogen-bonding to water.

Q: What is the function of lipopolysaccharides (LPS) in bacteria?

A: They act as dominant surface features on gram-negative bacteria and can trigger immune responses.

Q: Why is glycomics important?

A: It characterizes all carbohydrate components of cells and tissues, including those attached to proteins and lipids.