Biology Chapter: Chemical Basis of Life

Chemical Basis of Life

• Living organisms are composed of hydrogen, oxygen, nitrogen, and carbon.
• 99% of living matter is these four elements.
• Carbon atoms bond together with hydrogen atoms.

Organic Compounds

• Proteins, enzymes, nucleic acids (RNA and DNA), carbohydrates, and lipids are organic compounds.

Essential Elements in the Body

• 96% of the human body is composed of oxygen, carbon, hydrogen, and nitrogen.
• Other elements, such as calcium, phosphorus, potassium, and sulfur, are also present in smaller amounts.

Proteins (CHON)

• Proteins are the most abundant organic compounds in living cells.
• They are the fundamental components of cell protoplasm.
• Functions:
  • Essential for building and repairing body cells and tissues.
  • Act as enzymes to speed up the construction and repair of tissues.
  • Contribute to individual differences.
  • Function as transport molecules and provide protection as antibodies.

Amino Acids (Building Blocks of Proteins)

• Amino acids are the building blocks of proteins.
• Essential amino acids cannot be synthesized by the body and must be obtained through food.
• Nonessential amino acids can be synthesized by the body.

Enzymes

• Enzymes are special proteins that act as catalysts.
• They speed up chemical reactions without being consumed in the process.
• Example:
  • Salivary amylase breaks down starch into simple sugars in minutes.
  • Starch breaks down into simple sugars over longer time in high temperature and acidic environments.

Enzymes and the Body

• Enzymes play a crucial role in digestion, allowing the body to break down food into usable components.
• Enzymes are needed for every system in the body such as heptic, circulatory, renal, nervous, cardiac, endocrine, neurologic, lymphatic and reproductive.
• They are also essential for building and maintaining skin, bone, and muscle tissue.

Nucleic Acid (RNA and DNA)

• Nucleic acids are complex organic molecules composed of carbon, oxygen, nitrogen, and phosphorus.
• DNA serves as the genetic material of all living things.
• DNA provides instructions for making proteins and enzymes.
• RNA is synthesized from DNA and plays a critical role in protein synthesis.
• DNA and RNA control the cell's chemical activities.

Carbohydrates

• Carbohydrates are organic compounds made of carbon, hydrogen, and oxygen (in a 1:2:1 ratio).
• They are the primary energy source for organisms.
• Types:
  • Monosaccharides (single sugar units): glucose, fructose, galactose
  • Disaccharides (double sugar units): sucrose, lactose, maltose
  • Polysaccharides (multiple sugar units): starch, glycogen, cellulose

Roles of Carbohydrates

• Source for other molecules.
• Energy storage (starch, cellulose, glycogen).
• Primary energy source for the body.
• Component in structural components of cells.

Lipids

• Lipids are another major class of organic compounds in living cells.
• They include fats and fat-like molecules which are insoluble in water.
• Functions: energy storage, protection, structural components of cell membranes, and signaling.
• Types: triglycerides, phospholipids, steroids, and waxes.
• Roles:
  • High-energy food source.
  • Thermal insulation for animals.
  • Structural component of cell membranes.
  • Building blocks for various steroids.