Ch 10 - Biomolecules12th Chemistry
Chemical Definition of Carbohydrates
Why is the historical general formula inadequate for defining carbohydrates, and what is the modern chemical definition?
Why is the historical general formula inadequate for defining carbohydrates, and what is the modern chemical definition?
The Formula Flaw:
- False Positives: Compounds like Acetic acid () fit the hydrate formula () but are not carbohydrates.
- False Negatives: True carbohydrates like Rhamnose () do not fit the hydrate formula.
Modern Chemical Definition:
Carbohydrates are defined strictly as optically active polyhydroxy aldehydes or ketones, or compounds that produce such units upon hydrolysis.
Prism Memory Hook
Carbs are Optically Active Polyhydroxy Aldehydes or Ketones (OAPAK).
Hydrolytic Classification of Carbohydrates
How are carbohydrates classified based on their behavior upon hydrolysis?
How are carbohydrates classified based on their behavior upon hydrolysis?
- Monosaccharides: Cannot be hydrolysed further into simpler units (e.g., Glucose, Fructose, Ribose).
- Oligosaccharides: Yield 2 to 10 monosaccharide units on hydrolysis. Subclassified into disaccharides (e.g., Sucrose, Maltose), trisaccharides, etc.
- Polysaccharides: Yield a large number of monosaccharide units on hydrolysis. They are generally not sweet (non-sugars) (e.g., Starch, Cellulose, Glycogen).
Prism Memory Hook
Mono means 1, Oligo means a few (2-10), Poly means many (greater than 10).
Reducing vs Non-Reducing Sugars
What is the defining chemical property of a reducing sugar, and which common disaccharide is a non-reducing sugar?
What is the defining chemical property of a reducing sugar, and which common disaccharide is a non-reducing sugar?
Defining Property:
Carbohydrates that can reduce Fehling's solution and Tollens' reagent are called reducing sugars. This happens when the aldehydic or ketonic (reducing) groups are free. All monosaccharides (aldoses and ketoses) are reducing sugars.
The Non-Reducing Exception:
Sucrose is a non-reducing sugar because the reducing groups of both glucose and fructose are involved in the glycosidic bond, leaving no free carbonyl group.
Prism Memory Hook
Free to React means Reducing. Sucrose is Stuck, so it is Non-reducing.
Also in this chapter
49 more cards to study in Prism
- 4Preparation of Glucose from Sucrose
- 5Commercial Preparation of Glucose (from Starch)
- 6Stereochemistry: D and L Nomenclature
- 7Structure of Glucose: Evidence for Straight Chain
- 8Structure of Glucose: Evidence for Carbonyl Group
- 9Anomalies of the Open-Chain Glucose Structure
- 10Structure of Glucose: Evidence for Aldehyde Group
- 11Structure of Glucose: Evidence for Five Hydroxyl Groups
- 12Structure of Glucose: Evidence for Primary Alcohol
- 13D and L Nomenclature System
- 14Cyclic Hemiacetal Structure & Anomers
- 15Cyclic Rings: Pyranose vs Furanose
- 16Stereochemical Structure of Fructose
- 17Glycosidic Linkage
- 18The Phenomenon of Invert Sugar
- 19Disaccharides: Composition of Sucrose
- 20Disaccharides: Composition of Maltose
- 21Disaccharides: Composition of Lactose
- 22Zwitterion & Amphoteric Nature of Amino Acids
- 23Polysaccharides: Starch Components
- 24Peptide Linkage Formation
- 25Polysaccharides: Structure of Cellulose
- 26Polysaccharides: Glycogen (Animal Starch)
- 27Amino Acids: Structure of Alpha-Amino Acids
- 28Classification: Essential vs Non-Essential Amino Acids
- 29Amino Acids: The Optically Inactive Exception
- 30Amino Acids: Isoelectric Point
- 31Proteins: The Four Levels of Structure
- 32Protein Secondary Structure: $\alpha$-Helix vs $\beta$-Pleated Sheet
- 33Protein Classification: Fibrous vs Globular
- 34Phosphodiester Linkage
- 35Proteins: Denaturation
- 36Enzymes: Biological Catalysts
- 37Vitamins: Etymology & Nomenclature
- 38Anomers vs Epimers
- 39Vitamins: Classification by Solubility
- 40Mutarotation
- 41Vitamins: Chemical Names (Water-Soluble)
- 42Fructose as a Reducing Sugar
- 43Osazone Formation
- 44Vitamins: Deficiency Diseases (A & B-Complex)
- 45Vitamins: Deficiency Diseases (C, D, E, K)
- 46Nucleic Acids: Chemical Composition (DNA vs RNA)
- 47Enzymatic Reduction of Activation Energy
- 48Nucleic Acids: Nucleoside vs Nucleotide
- 49Nucleic Acids: Secondary Structure of DNA
- 50Nucleic Acids: Biological Functions
- 51Nucleic Acids: DNA Fingerprinting
- 52Hormones: Chemical Classification
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