Biology Chapter: Elements and Molecules of Life

Elements of Life

• 96% of all living things are made from six elements: carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus (CHONSP)
• Oxygen accounts for 65% of the mass of a human
• The remaining 4% of elements in living things are considered trace elements, such as calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium

Molecules of Life

• Living organisms are formed by combining the six main elements in different ways
• The four main types of molecules in living things are carbohydrates, proteins, fats (lipids), and nucleic acids
• These molecules are built by combining smaller molecules called monomers
• Each molecule is made of a chain of repeating monomers called polymers

Monomers vs. Polymers

• A monomer is a single organic molecule
• A polymer is a large molecule made of many identical monomers linked together

Building Large Organic Molecules

• Monomers bond together to form polymers.
• This process requires energy and is called dehydration synthesis or condensation reaction

Dehydration Synthesis

• A process that uses energy to join monomers, forming larger molecules (polymers)
• This reaction removes water, releasing energy in the form of ATP and heat
• This is an endergonic reaction
• Enzymes help carry out dehydration synthesis

Breaking Down Polymers: Hydrolysis

• Hydrolysis breaks down polymers into smaller molecules (monomers)
• It adds water and releases energy in the form of ATP, making it an exergonic reaction
• Enzymes also help carry out hydrolysis

Example of Digestion

• Starch is broken down into glucose by hydrolysis, releasing energy

Why We Eat

• We eat to take in more chemicals for our bodies.
• We eat to get building materials to grow, repair, and create new cells
• We eat to get energy from food (calories) to produce ATP

Matter in the Human Body

• Living things are mostly made up of organic compounds
• Organic compounds contain carbon
• Inorganic compounds do not contain carbon
• Water is an example of an inorganic compound
• Biomolecules are examples of organic compounds

Arrangement of Elements in Organic Compounds

• Carbon atoms bond to other atoms, forming chains and rings.
• This bonding allows the formation of a diverse variety of organic molecules.