BiologyFlashcards
Periodic Table
How elements (pure substances) are organized.. Protons having a positive charge, electrons having a negative charge, and neutrons having no charge at all. Created by Dmitri Mendeleev (known for his great hair :P)
Henri Becquerel
In 1896, Henri left some crystals of uranium salt in his desk drawer which produced negative images on his film. This proved the existence of radioisotopes (he called them invisible radiations)
Radioactive Decay
The process of transforming one element into another. It occurs independently of external factors and it will always decay at a constant rate.
Tracer
Any molecule with a detectable substance attached. Typically, a radioactive tracer is a molecule in which radioisotopes have been swapped for 1+ atoms.
PET
Positron-Emission Tomography: allows people to see cell activity. The tracer, such as a radioactive sugar, is injected into a patient who is then moved into a PET scanner.Cells will take up the tracer at different rates and detects radioactive decay where ever the tracer is. This produces an image on a computer monitor and can reveal cell abnormalities.
Shell Model
Used to check the cell for vacancies. (check out figure 2.6 and 2.7 on page 24 and 25)
Electronegativity
The measure of an atom’s ability to pull electrons from other atoms. Whether the pull is strong or weak depends on the atoms size and how many vacancies it has; it is not a measure of charge.
Chemical Bond
An attractive force that arises between 2 atoms when their electrons interact.
Molecule
Formed when 2+ atoms of the same or different elements join in chemical bonds.
Compounds
are molecules that consist of 2+ different elements in proportions that do not vary. (ex. water)
Mixture
2+ substances intermingle, and their proportions can vary because the substances do not bond with each other (ex. sugar in water)
Ionic Bonds
Bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other.
Covalent Bonds
bond in which one or more pairs of electrons are shared by two atoms. A line represents a single covalent bond, 2 lines represents a double covalent bond, and 3 lines represents a triple covalent bond. See table 2.1, 2.8, 2.9 on page 26 and 27
Polar Covalent Bond
forms between 2 elements with a small different in electronegativity. The atoms do not share electrons equally.
Non-polar Covalent Bonds
2 atoms of identical electronegativity share electrons equally and there is no difference of charge between the 2 ends of the bond.
Polarity
separation of charge into distinct positive and negative regions.
Hydrogen Bond
an attraction between an hydrogen atom and an electronegative atom, both of which are taking part in separate polar covalent bonds. (Table 2.10 page 27)
Hydrophilic
Molecules which will likely form bonds with water due to its polarity. Polar molecules and sugars are likely to form bonds with water.
Hydrophobic
Molecules that will not likely form bonds with water such as oil molecules.
Temperature
How the energy of molecular motion is measured.
Water Molecule
Has a bent shape with a slightly negative end (oxygen) that is balanced by its slightly positive ends (hydrogen) See table 2.11 page 28
Evaporation
When the temperature of water is below its boiling point hydrogen bonds form as fast as they break. While the water gets hotter the increase in molecular motion keeps bonds from forming so individual molecules at the surface escape into the air.
Benefits of Evaporation
cooling off when you sweat in hot, dry weather.
Solvent
Is a substance (usually a liquid) which dissolves other substances.
Solute
The substance which is dissolved.
Sphere of hydration
A cluster of water molecules around a solute. Such spheres form around any solute in cellular fluids, tree sap, blood, the fluid in your gut, and all fluids associated with life.
Cohesion
Molecules resist separating from one another which allows for surface tension. Cohesion also works inside organisms (ex. plants absorb nutrient-laden water while they grow).
pH scale
the measure of hydrogen ion concentration in solutions. The greater the H+ concentration the lower the pH (see table 2.14 page 30)
Acids
Donate hydrogen ions
Bases
Accept Hydrogen ions
Weak Acids
stingy H+ donors (carbonic acid)
Strong Acids
readily give up H+ in water (hydrochloric acid)
Buffer System
A set of chemicals (often a weak acid or base) which keeps a solution stable
Buffer System Failure
Ex Acute respiratory acidosis causes carbon dioxide to accumulate and form excess carbonic acid in the blood.
Strong Acids and Bases
Can kill organsims and cause severe chemical burns
Salt
Any compound which will dissolve easily into water other than H+ and OH-
