The Chemistry of Life Ch. 4.1-4.3

Recall: Levels of Organization

Biology Depends on Chemistry In our biosphere, everything is made of atoms Through the interaction of chemicals we can better understand our biosphere

Atoms Basic unit of matter Protons Neutrons Electrons (+) charge In nucleus Neutrons (0) charge Electrons (-) charge Around nucleus at varying energy levels

Molecules 2 or more atoms held together by chemical bonds Importance to biology: macromolecules make up cells and cellular components

Chemical Bonds: Ionic Electrons transferred from one atom to another Ex: NaCl (salt) Importance to biology: many salts are made this way (homeostatic balance)

Chemical Bonds: Covalent Electrons are shared between atoms Ex: CO2 Importance to biology: carbon compounds, water

Chemical Bonds: Hydrogen Weak bond formed from by the attraction of two electronegative molecules Slightly positive, slightly negative ends Importance to biology: critical to water’s properties, holds DNA together

Chemical Reactions Synthesis Decomposition Make a compound Ex: Photosynthesis Decomposition Break down a compound Ex: Cellular Respiration Both reactions important to biology: metabolism