CHEM 113 Prelims

• Biochemistry is the study of the chemical substances found in living organisms and the chemical interactions of these substances with each other
• New discoveries are made almost daily about how cells manufacture the molecules needed for life and how the chemical reactions by which life is maintained occur
• The knowledge explosion in biochemistry during the last decades of the twentieth century and the beginning of the twenty-first is phenomenal
• Biochemical substances are divided into two groups: bioinorganic substances and bioorganic substances
• Bioinorganic substances include water and inorganic salts
• Bioorganic substances include carbohydrates, lipids, proteins, and nucleic acids
• Although the human body is usually thought of as containing mainly organic (biochemical) substances, such substances make up only about one-fourth of total body mass
• Water constitutes more than two-thirds of the mass of the human body
• Another 4%–5% of body mass comes from inorganic salts
• Bioinorganic and bioorganic substances, when gathered together in a cell, have chemical interactions that sustain life
• Carbohydrates are the most abundant class of bioorganic molecules on planet Earth
• In the human body, carbohydrates constitute about 75% by mass of dry plant materials
• Green plants produce carbohydrates via photosynthesis
• Photosynthesis involves carbon dioxide from the air, water from the soil, and sunlight absorbed by chlorophyll as the energy source
• Plants use carbohydrates in two main ways:

  • Cellulose serves as structural elements
  • Starch provides energy reserves
• Dietary intake of plant materials is the major carbohydrate source for humans and animals
• The average human diet should ideally be about two-thirds carbohydrate by mass