Ch 2 The Chemical Context of Life. I. Overview. All living organisms are subject to the laws of chemistry & physics. A basic knowledge of both helps us to better understand how living things work. 1. What class of levers do you find most often in the human body? 2. Why use those?
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1. What class of levers do you find most often in the human body?
2. Why use those?
3. How do moth species recognize mates of the same species?
4. Read the test case on the “Devil’s gardens” in the rain forest in Ch 2.
A. Matter- anything that has mass and takes up space
1. Matter consists of chemical elements in pure form or in combinations called compounds
2. All organisms have mass & take up space, therefore all organisms are made of matter
1. Elements are substances that can’t be broken down into other substances by chemical reactions
A compound is a substance consisting of two or more different elements chemically combined in a fixed ratio.
1. Compounds will have chemical and physical characteristics different from those of their elements.
2. ex. Salt is made of Sodium (Na) and Chlorine (Cl). Sodium explodes in water, chlorine is a poison. Salt is a harmless, edible compound.
(CHON) or (CHONS)
All atoms of an element have the same number of protons, but may have different numbers of neutrons in the nucleus.
1. dating fossils
2. diagnosing medical problems
3. tracing atoms through metabolic processes
1. Electrons’ potential energy is due to their energy level or position in an electron shell.
2. Electrons losing energy, fall to a lower shell.
Valence electrons are those in the outermost or valence shell of the atom.
1. The shared electrons each count as part of each other’s valence shell
1. Single covalent bond- made by the sharing of one pair of electrons
2. Double covalent bond- made by the sharing of two pairs of electrons
3. Triple covalent bond- made by the sharing of three pairs of electrons
ex. H H
1. -Indicates a partially positive charge on the atom
2. -Indicates a partially negative charge on the atom
3.So, the oxygen atom is slightly negative (it has the electrons most of the time) and the hydrogen atoms are partially positive.
The red electron on sodium is transferred to Chlorine. This leaves 8 electrons in the remaining outer electron shell for sodium and completes the valence shell for chlorine with the 8th electron, making an ionic bond.
1. reinforce the shapes of large molecules
2. help molecules adhere to each other
Unequally shared electrons in a molecule or atom cause “hot spots” of positive or negative charge
Biological molecules recognize & react with each other based on the specific shape of the molecules.
(see picture to the left)
Some reactions are not reversible but may be paired with an opposite reaction. An example is photosynthesis & respiration.
CO2 + H2O C6H12O6 + O2
C6H12O6 + O2 CO2 + H2O
Acknowledgements: This presentation is drawn almost entirely from the materials provided by Reese Campbell 8th ed. DVD materials & notes