BI 315 SYSTEMS PHYSIOLOGY CHAPTER 2 NOTES

BI 315 SYSTEMS - Chapter 2 Chemical Composition of the Body Notes Atoms unit of matter that form all chemical substances Chemical Element Each type

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Chapter 2 Chemical Composition of the Body: Notes Atoms: unit of matter that form all chemical substances. Chemical Element: Each type of atom. Proton-Positive charged subatomic particle. Electron-Negatively charged subatomic particle. Neutron- neutrally charged subatomic particle. Atomic Nucleus- center of an atom comprised of protons and neutrons. Electrons revolve in orbitals around nucleus. Each orbital can hold 2 electrons. Atom most stable when all orbital’s in outermost energy shell filled. Nucleus has a net positive charge. Major force that holds atoms together is the force between the positive nucleus and the negative electron orbital’s. Each chemical element has its own specific number of protons. Atomic number: Number of protons specific to a chemical element. Atomic weight- atom’s mass, relative to the mass of other atoms. This scale based on assigning carbon atom a mass of 12. Unit of atomic mass is a Dalton. One Dalton is 1/12 the mass of carbon. Isotopes-The same chemical elements that differ in the number of neutrons they contain. One gram atomic mass of a chemical element is the amount of the element, in grams, equal to the numerical value of its atomic weight. Ion-when an atom gains or loses one or more electrons, it acquires a net electrical charge. Cations- Positive charged ions. Anions- Negatively charged ions. Ions are able to conduct electricity when dissolved in water. Electrolytes- ionic forms of mineral elements. Hydrogen, Oxygen, Nitrogen and Carbon ~99% body’s atoms. 7 essential mineral elements-most abundant substances dissolved in the extracellular and intracellular fluids. (Calcium and Phosphorus Bone tissue) 13 essential trace elements- Iron plays a role in blood’s transport of oxygen. Table 2-1 Molecule- two or more atoms bonded together. A molecule made up of 2 or more different elements is a compound. O2=molecule while H2O=compound. Covalent bond- one or more electrons in the outer electron orbital’s of each atom are shared between 2 atoms. Electronegativity- Measure of an atom’s ability to attract electrons in a covalent bond. Increases as the total positive charge in the nucleus increases but decreases as the distance between shared electrons and the nucleus increases. Higher electronegative atoms create polar molecules.
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Polar covalent- bonds in which one atom acquires a slight negative charge because of high electronegativity, and another atoms acquires a slight positive charge because of partially losing an electron. -OH group polar covalent. (Hydroxy) Polar molecules are soluble in water. Polar Molecules readily dissolve in blood, interstitial fluid and intracellular fluid. Nonpolar Molecules-Bonds between molecules with similar electronegativities.
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This note was uploaded on 03/01/2011 for the course BI 315 taught by Professor Widmaier during the Spring '09 term at BU.

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BI 315 SYSTEMS - Chapter 2 Chemical Composition of the Body Notes Atoms unit of matter that form all chemical substances Chemical Element Each type

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