Basic Molecules of Life (Exam Review)
Ch.2 Essential chemistry for Biology
1. Water is precious to life because living organisms use water as the medium (solvent) for chemical reactions necessary to sustain life. Water also helps maintain temperatures. Droughts are disastrous because they can wipe out crops, which in turn cause famine.
2. MATTER: Composed of chemical elements, occupies space and has mass (ex: solid, liquid, and gas states.) CHEMICAL ELEMENTS: substance that cannot be broken down into other substances by chemical reactions (ex: carbon, oxygen, gold). COMPOUNDS: Substances that contain two or more elements in a fixed ratio (ex: table salt = equal parts sodium (NA) and chlorine (Cl)=NaCl)
3. ATOMIC NUMBER= # of protons MASS NUMBER= pro + neutrons
4. An Isotope is an element with the same number of protons and electrons but a different number of neutrons. RADIOACTIVE ISOTOPES the nucleus decays spontaneously giving off particles and energy. Useful for tracing cells in the body when they pick up this radioactive isotope.
5. The farther an electron is from the nucleus, the greater its energy. Numbers of electrons in the outermost shell determines the chemical properties of an atom. Outer shells that are not full interact with other atoms, however shells that are full (ie: helium with 2 electrons), are chemically unreactive.
6. IONIC BONDS: transfer of electrons between two oppositely charged ions causes them to be attracted to each other (x-,x+) (example: Na11,Cl17>Na->1e to Cl>Na+10,Cl-18). COVALENT BONDS: form when two atoms share one or more pairs of outer-shell electrons (ex: methane=CH4, Carbon with 4 hydrogen molecules attached to its outer shell, because carbon has 4 spots open in its outer shell).HYDROGEN BONDS: in water, H2o, the 2 hydrogens share electrons with the 1 oxygen, making oxygen slightly – and hydrogen slightly + (a polar molecule is one with an uneven distribution of charge), these opposing charges attract each other.
7. Water is structured so that the (-)part
1. Water is precious to life because living organisms use water as the medium (solvent) for chemical reactions necessary to sustain life. Water also helps maintain temperatures. Droughts are disastrous because they can wipe out crops, which in turn cause famine.
2. MATTER: Composed of chemical elements, occupies space and has mass (ex: solid, liquid, and gas states.) CHEMICAL ELEMENTS: substance that cannot be broken down into other substances by chemical reactions (ex: carbon, oxygen, gold). COMPOUNDS: Substances that contain two or more elements in a fixed ratio (ex: table salt = equal parts sodium (NA) and chlorine (Cl)=NaCl)
3. ATOMIC NUMBER= # of protons MASS NUMBER= pro + neutrons
4. An Isotope is an element with the same number of protons and electrons but a different number of neutrons. RADIOACTIVE ISOTOPES the nucleus decays spontaneously giving off particles and energy. Useful for tracing cells in the body when they pick up this radioactive isotope.
5. The farther an electron is from the nucleus, the greater its energy. Numbers of electrons in the outermost shell determines the chemical properties of an atom. Outer shells that are not full interact with other atoms, however shells that are full (ie: helium with 2 electrons), are chemically unreactive.
6. IONIC BONDS: transfer of electrons between two oppositely charged ions causes them to be attracted to each other (x-,x+) (example: Na11,Cl17>Na->1e to Cl>Na+10,Cl-18). COVALENT BONDS: form when two atoms share one or more pairs of outer-shell electrons (ex: methane=CH4, Carbon with 4 hydrogen molecules attached to its outer shell, because carbon has 4 spots open in its outer shell).HYDROGEN BONDS: in water, H2o, the 2 hydrogens share electrons with the 1 oxygen, making oxygen slightly – and hydrogen slightly + (a polar molecule is one with an uneven distribution of charge), these opposing charges attract each other.
7. Water is structured so that the (-)part