Lesson 3 Carbohydrates, Part 1 (Part 2)

Summary

This script delves into the world of carbohydrates, focusing on oligosaccharides and polysaccharides. It explains oligosaccharides as polymers of 3 to 9 sugar units, crucial for cell recognition and exemplified by blood type markers on red blood cells. Polysaccharides, made of many monosaccharides, include cellulose, chitin, starch, and glycogen, serving various functions like structural support and energy storage. The script also touches on monosaccharide reactions like oxidation, reduction, and glycoside formation, highlighting their importance in biological processes.

Takeaways

• 🔬 Oligosaccharides are polymers composed of 3 to 9 monosaccharide units linked by glycosidic bonds.
• 🌐 They are typically found attached to cellular structures, such as being bound to sphingolipids or proteins.
• 🆔 Oligosaccharides play a crucial role in cellular identity and recognition, acting as a sort of cellular barcode or ID.
• 🩸 An example of oligosaccharides' function is in determining blood types, with ABO blood markers being oligosaccharides containing three or four sugar units.
• 🚫 Type O blood is the universal donor because its oligosaccharides are a subset of those found in other blood types, whereas type AB is the universal receiver.
• 🍚 Polysaccharides are complex carbohydrate molecules made up of many monosaccharides linked together.
• 🌾 Examples of polysaccharides include cellulose, chitin, starch, and glycogen, which serve various functions like structural support and energy storage.
• 🔗 The type of glycosidic linkage (alpha or beta) in polysaccharides determines their function, with cellulose and chitin having beta linkages and starch and glycogen having alpha linkages.
• 🌱 Cellulose is a major structural component of plants, composed of beta D-glucose units, while chitin provides structural support in invertebrates like insects and crustaceans.
• 🥔 Starch, found in plants, and glycogen, found in animals, are energy storage polysaccharides with alpha glycosidic linkages.
• 🔄 Monosaccharides undergo various chemical reactions including oxidation, reduction, isomerization, esterification, and glycoside formation.

Q & A

What are oligosaccharides?

Oligosaccharides are polymers composed of 3 to 9 monosaccharide units joined by glycosidic bonds. They are typically found attached to cellular structures and play a crucial role in cellular identity and recognition.

How do oligosaccharides function in cell recognition?

Oligosaccharides act as a barcode or ID on the cell surface, particularly in the plasma membrane, allowing cells to be recognized by other cells in the body.

What is the significance of oligosaccharides in blood type determination?

The type of oligosaccharides present on the surface of red blood cells determines a person's blood type. These oligosaccharides contain either three or four sugar units.

Why is blood type O considered a universal donor?

Blood type O is considered a universal donor because the saccharide units found in type O blood are also found in other blood types, making it less likely to cause a reaction when donated.

What are polysaccharides?

Polysaccharides are polymeric carbohydrate molecules made up of many monosaccharides linked together by glycosidic linkages.

What are the two types of polysaccharides?

There are two types of polysaccharides: homopolysaccharides, which are made up of only one type of monosaccharide, and heteropolysaccharides, which are made up of different types of monosaccharides.

What is the role of cellulose in plants?

Cellulose is a major structural component of plants, particularly in wood and plant fibers. It provides mechanical strength due to hydrogen bonding between its linear chains of beta D-glucose units.

How does starch differ from cellulose?

Starch differs from cellulose in that it is a storage carbohydrate in plants, with alpha glycosidic linkages instead of beta. It is composed of amylose (linear) and amylopectin (branched) chains.

What is glycogen and where is it typically found?

Glycogen is a highly branched polymer of alpha D-glucose that serves as a stored carbohydrate in animals. It is typically found in the liver and muscle cells.

What are the five reactions that monosaccharides can undergo?

Monosaccharides can undergo oxidation, reduction, isomerization, esterification, and glycoside formation.

How does the oxidation of glucose provide energy for cells?

The oxidation of glucose is a process that generates energy in the form of ATP through cellular respiration, involving the transfer of electrons and the production of acids like gluconic acid.