BIO 202 Lecture 1

BIO 202 Lecture 1 - Atoms and Molecules in Biology The...

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Atoms and Molecules in Biology
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The hierarchy of biological order BIO 202
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Sizes of molecules, cells and organisms
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Chemical elements in living cells
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Elements • Element = a substance that cannot be broken down by chemical reactions • There are 92 naturally occurring elements (+artificial=>103) • Each element has a 1- or 2-letter symbol (e.g., O, N, Na, Ca) • Life requires ~25 elements • Trace elements = elements required in minute amounts, but their lack can cause severe disorders • Elements are made of atoms • Atom is the smallest unit of matter that retains the properties of an element
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Structure of atoms Atoms are made of subatomic particles: Protons and neutrons make up the atomic nucleus •Neutron mass = Proton mass = 1.7 x 10 -24 g = 1 Dalton •Neutron = 0 charge •Proton = +1 charge •Thus, atomic nucleus is positively charged , and its mass = mass of protons+mass of neutrons
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• The nucleus is orbited by electrons • Electron charge = -1 • The attraction between the nucleus and the electrons keeps the electrons in the vicinity of the nucleus, and thus preserves the atomic structure • Atoms overall are neutral: # protons = # electrons • Electron mass = 1/2000 (=0.05%) mass of a
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BIO 202 Lecture 1 - Atoms and Molecules in Biology The...

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