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1. Introduction to Biochemistry4h 34m
2. Water3h 23m
3. Amino Acids8h 10m
4. Protein Structure10h 4m
5. Protein Techniques14h 5m
6. Enzymes and Enzyme Kinetics13h 38m
7. Enzyme Inhibition and Regulation 8h 42m
8. Protein Function 9h 41m
9. Carbohydrates7h 49m
10. Lipids5h 49m
11. Biological Membranes and Transport 6h 37m
12. Biosignaling9h 45m
Review 1: Nucleic Acids, Lipids, & Membranes2h 47m
Review 2: Biosignaling, Glycolysis, Gluconeogenesis, & PP-Pathway3h 12m
Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism2h 26m
Review 4: Amino Acid Oxidation, Oxidative Phosphorylation, & Photophosphorylation1h 48m

9. Carbohydrates

Disaccharides

9. Carbohydrates

Disaccharides: Videos & Practice Problems

Video Lessons Practice Worksheet

Topic summary

Disaccharides are sugars formed from two monosaccharides, with key examples including maltose, cellobiose, lactose, and sucrose. Maltose, linked by an alpha-1,4 glycosidic bond, is digestible and found in starch. Cellobiose, with a beta-1,4 linkage, is not digestible by most mammals. Lactose, composed of glucose and galactose with a beta-1,4 bond, is generally digestible, though some individuals are lactose intolerant. Sucrose, made of glucose and fructose with a beta-1,2 linkage, is also digestible. Understanding these configurations is crucial for grasping their digestibility and biological roles.

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Disaccharides

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Disaccharides Video Summary

Disaccharides are sugars composed of two monosaccharides linked together by a glycosidic bond. Among the numerous disaccharides found in nature, four of the most significant are maltose, cellobiose, lactose, and sucrose. Each of these disaccharides has unique structures and properties that influence their digestibility.

Maltose consists of two D-glucose units connected by an α-1,4-glycosidic linkage. It is commonly found in starch, which is present in many plant-based foods like potatoes, making maltose digestible for most mammals.

Cellobiose also comprises two D-glucose units, but they are linked by a β-1,4-glycosidic linkage. This structural difference means that, despite having the same sugar components as maltose, cellobiose is not digestible by most mammals. This highlights the importance of glycosidic bond configuration in determining digestibility.

Lactose, the sugar found in milk, is formed from one D-galactose and one D-glucose unit, linked by a β-1,4-glycosidic linkage. While lactose is generally digestible for most mammals, some individuals may be lactose intolerant, which affects their ability to digest this disaccharide.

Sucrose, commonly known as table sugar, consists of a D-glucose and a D-fructose unit. The glycosidic linkage in sucrose is more complex, involving both an α-1 and a β-2 glycosidic linkage. Sucrose is widely found in processed foods and is digestible by most mammals.

In summary, the digestibility of these disaccharides is influenced by their structural configurations. Maltose is digestible, cellobiose is not, while lactose and sucrose are generally digestible. Understanding these differences is crucial for recognizing how various sugars affect nutrition and metabolism.

Problem

Which of the following contains galactose as one of the sugar subunits?

Glucose.

Ribose.

Maltose.

Lactose.

Cellobiose.

Problem

Which disaccharide forms a 1,1-glycosidic linkage?

Lactose.

Trehalose.

Maltose.

Sucrose.

Problem

What is the identity of the disaccharide below?

Cellulose.

Lactose.

Chitin.

Maltose.

Sucrose.

Cellobiose.

Glycogen.

Problem

The structure of a disaccharide is shown below. Which statement applies?

Both sugar rings A and B are in equilibrium with their linear chain forms.

Only sugar ring A is in equilibrium with its linear chain form.

Only sugar ring B is in equilibrium with its linear chain form.

Neither sugar ring is in equilibrium with their linear chain form.

None of the above statements are correct.

Problem

Name each monosaccharide unit & the glycosidic linkage in the following disaccharide (gentiobiulose).

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Problem

Given the following information, draw a Haworth projection for the disaccharide gentibiose:
1. Gentibiose is a dimer of glucopyranoses.
2. The glycosidic linkage is β(1 → 6).
3. The anomeric carbon not involved in the glycosidic linkage is in the α configuration.

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What are the main types of disaccharides and their components?

The main types of disaccharides are maltose, cellobiose, lactose, and sucrose. Maltose consists of two D-glucose molecules linked by an alpha-1,4 glycosidic bond. Cellobiose also consists of two D-glucose molecules but is linked by a beta-1,4 glycosidic bond. Lactose is composed of one D-galactose and one D-glucose molecule, connected by a beta-1,4 glycosidic bond. Sucrose is made up of one D-glucose and one D-fructose molecule, linked by a beta-1,2 glycosidic bond. Understanding these components and linkages is crucial for grasping their digestibility and biological roles.

Why is cellobiose not digestible by most mammals?

Cellobiose is not digestible by most mammals because it has a beta-1,4 glycosidic linkage between its two D-glucose molecules. Most mammals lack the enzyme necessary to break this specific type of glycosidic bond. In contrast, maltose, which has an alpha-1,4 glycosidic linkage, is digestible because mammals possess the enzyme to hydrolyze this bond. The configuration of the glycosidic bond plays a crucial role in determining whether a disaccharide is digestible.

What is the difference between maltose and cellobiose?

Maltose and cellobiose both consist of two D-glucose molecules, but they differ in their glycosidic linkages. Maltose has an alpha-1,4 glycosidic bond, making it digestible by most mammals. Cellobiose, on the other hand, has a beta-1,4 glycosidic bond, which is not digestible by most mammals. This difference in the configuration of the glycosidic bond significantly affects their digestibility and biological roles.

What is the significance of glycosidic linkages in disaccharides?

Glycosidic linkages in disaccharides are crucial because they determine the structure, digestibility, and biological function of the sugar. For example, maltose has an alpha-1,4 glycosidic bond, making it digestible, while cellobiose has a beta-1,4 bond, making it indigestible by most mammals. Lactose has a beta-1,4 bond but is generally digestible, except for those who are lactose intolerant. Sucrose has a beta-1,2 linkage and is digestible. The type of glycosidic bond affects how enzymes interact with the disaccharide, influencing its breakdown and absorption in the body.

Why are some people lactose intolerant?

Lactose intolerance occurs when individuals lack sufficient levels of lactase, the enzyme required to break down lactose into glucose and galactose. Lactose is a disaccharide found in milk, composed of one D-galactose and one D-glucose molecule linked by a beta-1,4 glycosidic bond. Without enough lactase, lactose remains undigested in the intestine, leading to symptoms like bloating, gas, and diarrhea. This condition varies in severity and is more common in certain populations.