Class notes
Biology Chapter 2 -The Chemical Context of Life
- Course
- BIO 2900
- Institution
- Indiana Tech - Fort Wayne
Biology Chapter 2 -The Chemical Context of Life
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Key Concepts:- Matter consists of chemical elements in pure form and in combinations called
compounds
- An element's properties depend on the structure of its atoms
- The formation and function of molecules and ionic compounds depend on chemical
bonding between atoms
- Chemical reactions make and break chemical bonds
Elements and Compounds
- Matter - anything that takes up space and has mass
- Element - substance that cannot be broken down by chemical means
- Compound - substance of two or more elements in fixed ratio
- Compound characteristics (emergent properties) different than constituent
elements
- Properties of compounds depend on atoms and how they are bonded
Elements of Life
- Essential elements - 20-25% of the 92 natural elements are necessary for life
- Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter
- Most of the remaining 4% include calcium, phosphorus, potassium, and sulfur
- Trace elements - required by organisms in minute quantities
Atoms
- Atom - smallest unit of matter that still retains properties of an element
Atoms are composed of these subatomic particles
- Neutrons - no electrical charge
- Protons - positive charge
- Proton count determines an atom’s identity and inherent traits
- Electrons - negative charge
- Electron distribution determines ability for bond formation
- Neutrons and protons form the atomic nucleus
- Mass of both are almost identical and are measured in Daltons
- Electrons orbit around the nucleus
- Mass is so small that they are ignored when calculating the atomic mass
Atomic Number and Atomic Mass
- Atoms of various elements differ in the number of subatomic particles
- Atomic number - the number of protons in the element’s nucleus
- Atomic mass - the sum of protons and neutrons in the nucleus
- Total mass approximated by the mass number
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