Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

20. Carbohydrates

Polysaccharides

GOB Chemistry

20. Carbohydrates

Polysaccharides

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2:30 minutes

Problem 57c

Textbook Question

Melezitose, a carbohydrate secreted by insects, has the following Haworth structure:

c. Is melezitose a reducing sugar?

Verified step by step guidance

Step 1: Understand the concept of a reducing sugar. A reducing sugar is a carbohydrate that can act as a reducing agent because it has a free aldehyde group (-CHO) or a free ketone group (-C=O) in its open-chain form. This property allows it to reduce other compounds, such as Benedict's reagent.

Step 2: Analyze the structure of raffinose. Raffinose is a trisaccharide composed of galactose, glucose, and fructose. In its structure, the glucose unit is linked to the galactose and fructose units through glycosidic bonds.

Step 3: Determine if the glucose unit in raffinose has a free anomeric carbon. The anomeric carbon is the carbon derived from the carbonyl group (C=O) in the open-chain form of the sugar. If this carbon is involved in a glycosidic bond, it is not free and cannot participate in redox reactions.

Step 4: Evaluate the fructose unit in raffinose. Fructose is a ketose sugar, and its anomeric carbon can also be involved in glycosidic bonding. If both the glucose and fructose units have their anomeric carbons involved in glycosidic bonds, raffinose will not have a free reducing end.

Step 5: Conclude whether raffinose is a reducing sugar. Based on the analysis, if all anomeric carbons in raffinose are involved in glycosidic bonds, it cannot act as a reducing sugar. This means raffinose is a non-reducing sugar.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Reducing Sugars

Reducing sugars are carbohydrates that can donate electrons to another chemical, typically due to the presence of a free aldehyde or ketone group. This property allows them to reduce other compounds, which is a key characteristic in various biochemical reactions. Common examples include glucose and fructose, which can participate in redox reactions.

Raffinose Structure

Raffinose is a trisaccharide composed of galactose, glucose, and fructose. Its structure includes a galactose unit linked to a sucrose molecule, which is a combination of glucose and fructose. Understanding its structure is essential to determine its reactivity and whether it can act as a reducing sugar.

Haworth Projection

The Haworth projection is a way of representing the cyclic structure of carbohydrates, showing the arrangement of atoms in a ring form. This representation helps visualize the orientation of hydroxyl groups and other substituents, which is crucial for understanding the chemical properties and reactivity of sugars, including whether they are reducing or non-reducing.