Biology 101 - Chapter 2 Notes

Biology 101 - Chapter 2 Notes - Biology 101 Notes Chapter 2...

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Biology 101 Notes – Chapter 2 The Chemical Context of Life I. Matter consists of chemical elements in pure form and in combinations called compounds. a. Elements and Compounds 1. Organisms are composed of matter. aa. Matter- Anything that takes up space and has mass *Ex. 2. Matter is made up of elements aa. Element- A substance that cannot be broken down to other substances by chemical reactions *92 elements occurring in nature *Ex. Cu, C, O bb. Compound- A substance consisting of two or more different elements combined in a fixed ratio. *Ex. NaCl (matter has emergent properties) *A compound has characteristic diff from those of its elements. *O 2 and H 2 are pure elements, not compounds. b. Essential Elements of Life 1. About 25 of the 92 natural elements are essential to life. aa. Carbon, oxygen, hydrogen, and nitrogen make up 96% of living matter bb. P, S, Ca, K, and others make up remaing 4%. cc. Oxygen accounts for 65% of human body weight, the most 2. Effects of essential element deficiencies aa. Nitrogen deficiency in crops, results in little growth bb. Goiter, an enlarged thyroid gland, results from deficiency of iodine, a trace element. 3. Trace Elements- Those elements required by an organism in only minute quantities. aa. Iron is needed by all forms of life. II. An element’s properties depend on the structure of its atoms 1. Each element consists of a certain kind of atom that is diff from the atoms of any other element. aa. Atom- The smallest unit of matter that still retains the properties of an element. bb. Symbolize atoms w/ same abbreviation as the element. *C stands for both element carbon and 1 carbon atom. a. Subatomic Particles
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1. Subatomic Particles- Even tinier bits of matter that make up an atom. cc. Atomic Nucleus- The center of an atom. Composed of neutrons and protons. dd. Electrons move around the nucleus in a cloud. *Negative charge ee. Protons have a positive charge. *Give the nucleus a positive charge. ff. A neutron is neutral. gg. The attraction b/w opposite charges (+ of nucleus and – of electrons) causes the electron to stay at a distance from the nucleus. 2. The Dalton- (amu) A unit of measurement used to relate to minuscule objects such as subatomic particles and molecules. aa. Neutrons and protons have masses of 1 dalton bb. Electrons are too small to measure mass b. Atomic Number and Atomic Mass 1. All atoms of an element have the same number of protons in their nuclei. aa. Atomic Number-
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Biology 101 - Chapter 2 Notes - Biology 101 Notes Chapter 2...

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