Understanding Carbohydrates

What are carbohydrates, and what are their primary functions in living organisms? Provide three examples of common carbohydrates and their respective roles.

• Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen, typically with a hydrogen-to-oxygen ratio of 2:1 (as in water); their primary functions include providing energy, serving as structural components, and participating in cell recognition
  • Examples: glucose (energy source), starch (energy storage in plants), and cellulose (structural component in plant cell walls)

Describe the three main types of carbohydrates: monosaccharides, disaccharides, and polysaccharides. Give an example of each, and explain how they differ in terms of structure and complexity.

• Monosaccharides are simple sugars with the general formula (CH2O)n
  • Example: glucose
• Disaccharides consist of two monosaccharides joined by a glycosidic bond
  • Example: sucrose (glucose + fructose)
• Polysaccharides are complex carbohydrates composed of many monosaccharide units linked together in long chains
  • Example: starch (polymer of glucose)
• Monosaccharides are the simplest, disaccharides are two monosaccharides joined, and polysaccharides are long chains of monosaccharides, increasing in complexity and size

Explain the difference between reducing and non-reducing sugars. Provide an example of each, and describe a simple chemical test that can be used to distinguish between them.

• Reducing sugars have a free aldehyde or ketone group that can reduce other compounds, while non-reducing sugars do not
  • Example: glucose is a reducing sugar
  • Example: sucrose is a non-reducing sugar
• Benedict's test can distinguish them
  • Reducing sugars reduce the copper(II) ions in Benedict's reagent to copper(I) oxide, forming a colored precipitate, while non-reducing sugars do not react

Describe the process of photosynthesis and its importance in carbohydrate synthesis. What are the main reactants and products of this process, and how do they contribute to the overall carbon cycle?

• Photosynthesis is the process by which plants and other organisms convert light energy into chemical energy in the form of glucose or other carbohydrates
  • Reactants: carbon dioxide and water
  • Products: glucose and oxygen
• The overall reaction is 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
• This process removes carbon dioxide from the atmosphere and produces oxygen, contributing to the carbon cycle by incorporating atmospheric carbon into organic molecules

Explain the role of carbohydrates in energy storage in both plants and animals. What are the primary storage forms of carbohydrates in each case, and how are they synthesized and broken down to meet energy demands?

• In plants, carbohydrates are primarily stored as starch, a polymer of glucose
  • Synthesized through photosynthesis and stored in structures like amyloplasts
  • Broken down via hydrolysis during cellular respiration to release glucose for energy
• In animals, carbohydrates are stored as glycogen, primarily in the liver and muscles
  • Synthesized from glucose and stored in granules
  • Broken down via glycogenolysis to release glucose when energy is needed