Carbohydrates Flashcards
What are carbohydrates made of?
Carbohydrates are biological molecules made of carbon (C), hydrogen (H), and oxygen (O).
How are carbohydrates classified?
Carbohydrates are classified into monosaccharides, disaccharides, and polysaccharides based on their structure and complexity.
What is a monosaccharide?
A monosaccharide is the simplest form of carbohydrates, consisting of single sugar units. Its general formula is (CH₂O)n.
What are examples of monosaccharides?
Examples include:
- Glucose (C₆H₁₂O₆) – main respiratory substrate
- Fructose – found in fruits, very sweet
- Galactose – found in lactose
What are isomers of glucose?
α-glucose: The -OH group is below carbon 1.
β-glucose: The -OH group is above carbon 1.
What is a disaccharide?
A disaccharide is formed by two monosaccharides joined via a condensation reaction, creating a glycosidic bond (either 1,4 or 1,6).
What is the process for breaking down disaccharides?
Disaccharides are broken down by a hydrolysis reaction (addition of water) to break the glycosidic bond, catalyzed by specific enzymes:
- Maltase → Maltose → 2 Glucose
- Sucrase → Sucrose → Glucose + Fructose
- Lactase → Lactose → Glucose + Galactose
What is a polysaccharide?
A polysaccharide is a large, complex carbohydrate made from many monosaccharides linked by glycosidic bonds.
What are the types of polysaccharides and their functions?
- Starch: Energy storage in plants (made of α-glucose, includes amylose and amylopectin).
- Glycogen: Energy storage in animals (made of α-glucose, highly branched).
- Cellulose: Provides structural support in plants (made of β-glucose).
What are the properties of starch?
- Amylose: Long, unbranched chain (1,4 glycosidic bonds), coiled.
- Amylopectin: Branched (1,4 and 1,6 glycosidic bonds), allows rapid glucose release.
- Insoluble, compact, and easily hydrolyzed to glucose.
What are the properties of glycogen?
- Highly branched (more than amylopectin).
- Insoluble and compact.
- More branching leads to faster hydrolysis by enzymes.
What are the properties of cellulose?
- Long, unbranched chains made of β-glucose.
- Hydrogen bonds form microfibrils, providing rigidity.
- Insoluble and strong.
- Cannot be digested by humans (due to lack of cellulase enzyme).
How do you test for reducing sugars?
- Add Benedict’s reagent (blue) to the sample.
- Heat in a water bath (80°C) for 5 minutes.
- Observe the color change: Blue → Green → Yellow → Orange → Brick-red precipitate (indicating high sugar concentration).
How do you test for non-reducing sugars?
- Perform Benedict’s test (no color change = negative).
- Add dilute HCl to hydrolyze the disaccharide.
- Neutralize with alkali (sodium hydrogen carbonate).
- Re-do the Benedict’s test: Positive result shows a brick-red precipitate.
Why are polysaccharides ideal for energy storage?
- Compact: Store large amounts of glucose in a small space.
- Insoluble: Prevents osmotic imbalance in cells.
- Easily hydrolyzed: Glucose can be quickly released for respiration.
- Branched (e.g., Glycogen & Amylopectin): More enzyme action, faster glucose release.
How do you test for starch?
- Add iodine solution (potassium iodide) to the sample.
- Positive result: Blue-black color (starch present).
- Negative result: Remains brown-orange (no starch).
