Basic Molecules of Life (Exam Review)

Topics: Cell, Protein, Bacteria Pages: 5 (1590 words) Published: March 10, 2013
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 of oxygen is always attracted to the (+)hydrogen, these hydrogen bonds help water keep its shape. (cohesion).The unequal sharing of negatively charged electrons along with the ’v’ shape water has makes it a polar molecule. 8.Cohesion- trees depend on the cohesion of water to be able to transport water up into its trunk. Temperature: water has a strong resistance to temperature change, such resistance helps stabilize ocean temperatures to help ocean dwelling organisms stay alive. Ice Floating: when cold, water molecules move farther apart and form ice, slows down the constantly changing hydrogen bonds in liquid water. Ice forms an insulating blanket over liquid water, allowing life to persist underneath. Solvent: Water is a solvent that can dissolve a variety of substances necessary for life (ie salt water). 9.An Acid releases H+ (hydrogen ions) into a solution, has a greater H+ concentration. A Base has a lower H+ concentration, base accepts H+ and removes them from the solution. A neutral solution has an equal amount of H+ and OH-. 10. Biological fluids contain buffers which minimize changes in pH by accepting H+ when in excess, and donating H+ when it is depleted.

Ch3: The Molecules of Life
1.Carbon has 4 open electron spots in its outermost shell ,allowing for it to form with a large variety of organic molecules. 2.Dehydration reactions allow monomers to link together to form polymers, when the polymer chain needs to be broken, hydrolysis occurs by adding a molecule of water into the chain. 3.MONOSACCHARIDES: smallest, simple sugar, monomers of carbs, main fuel molecule for cellular work. An example is fructose (C6H12O6).Shape=form rings when one part of the molecule forms a bond with another part of the molecule. DISACCHARIDES: double sugar, created from two monosaccharides via dehydration reaction. Ex is table sugar (sucrose), created from glucose monomer linked to a fructose monomer. Sucrose is the main carb in plant sap, nourshing the parts of...
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