Bio 1201 Chapter 2 -

Bio 1201 Chapter 2 - - Chapter 2 Chemical Context of Life...

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Chapter 2 Chemical Context of Life Atomic Structure: SPONCH and the Atom - 2.1.1 An understanding of chemistry is important because an interaction between atoms is one of the lowest levels of biological organization. SPONCH – you are more than 99% sulfur, phosphorous, oxygen, nitrogen, carbon, hydrogen *matter – anything that takes up space and has mass Matter exists in many forms and each has its own characteristics Matter is made up of elements *mass – is the amount of matter in an object *element – substance that cannot be broken down to other substances by chemical reactions; 92 elements Approximately 25 of the elements are essential for life. Of those the most biologically important by percentage are (see table 2.1): S = sulfur-4% of weight P = phosphorous -4% of weight O = oxygen - 96% living matter N = nitrogen –96% living matter C = carbon – 96% living matter H = hydrogen-96% living matter K = potassium -4% of weight Ca = calcium-4% of weight Na = sodium-4% of weight Cl = chlorine-4% of weight Mg = magnesium-4% of weight I. Trace Elements – those required by an organism in only minute quantities A. Some trace elements (FE) are needed by all forms of life, others are required only by certain species II. Characteristics of Atoms Each element consists of a certain kind of atom that is different from the atoms of any other element A. atom – smallest unit of matter that still retains the properties of an element B. Atoms are made up of subatomic particles. The 3 most stable subatomic particles are: neutrons, protons, and electrons. (see fig 2.4)
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1. Neutrons and protons are packed tightly together to form a dense core, atomic nucleus 2. Protons – electrically charged; positive 3. Neutrons – electrically neutral 4. Electrons – move at nearly the speed of light and form a cloud around the nucleus; electrically charged; negative 5. Because the nucleus is positively charged, the electrons cloud around the nucleus b/c of the opposite attraction 6. Dalton is a mass unit for subatomic particles. 1 Dalton = 1.67 x 10-24g C. Atomic number – number of protons in the nucleus D. Atomic mass or mass number – sum of protons plus the neutrons in the nucleus Mass # 23 Na Atomic # 11 E. All atoms of a given element have the same number of protons, but some have more neutrons than other atoms of the same element making it have a greater mass; different atomic forms are called
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Bio 1201 Chapter 2 - - Chapter 2 Chemical Context of Life...

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