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LIFESCI 7A Study Guide - Spring 2018, Comprehensive Midterm Notes - Enzyme, Dna, Chromosome


Department
Life Sciences
Course Code
LIFESCI 7A
Professor
Roth- Johnson
Study Guide
Midterm

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LIFESCI 7A
MIDTERM EXAM
STUDY GUIDE
Fall 2018

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WEEK 1
2.1: Atoms and their properties
Elements: A pure substance, such as oxygen, copper, gold, or sodium, that cannot be further
broken down by the methods of chemistry.
Atom: the basic unit of matter
Atoms consist of protons, neutrons, and electrons.
nucleus (of an atom): The dense central part of an atom containing protons and neutrons.
proton: A positively charged particle in the atomic nucleus.
electron: A negatively charged particle that moves around the atomic nucleus.
atomic mass: The mass of the atom determined by the number of protons and neutrons.
isotopes: Atoms of the same element that have different numbers of neutrons.
ion: An electrically charged atom or molecule (+ or -).
Electrons occupy regions of space called orbitals
orbital: A region in space where an electron is present most of the time.
shell: An energy level in which an orbital can exist.
Note; Rutherford’s gold foil experiment: atoms are made up of mostly empty space and a
small, densely packed nucleus
Elements have recurring, or periodic, chemical properties
periodic table of the elements: The arrangement of the chemical elements in tabular form,
organized by their chemical properties.
2.2: Molecules and Chemical Bonds
molecule: A substance made up of two or more atoms.
chemical bond: Any form of attraction between atoms that holds them together.
A covalent bond results when two atoms share electrons
valence electrons: The electrons farthest from the nucleus, which are at the highest energy
level; combine with other valence electrons to form molecule
molecular orbital: A merged orbital traversed by a pair of shared electrons.
covalent bond: A chemical bond formed by a shared pair of electrons holding two different
atoms together.
double bond: A covalent bond in which covalently joined atoms share two pairs of electrons.
Note: bonding follows the octet rule!
An ionic bond forms between oppositely charged ions
ionic bond: The association of two atoms resulting from the attraction of opposite charges;
instead of sharing electrons, it’s as if one atom steals from the other (NaCl)
A chemical reaction involves breaking and forming chemical bonds
chemical reaction The process by which molecules are transformed into different molecules.
Atoms retain identity but bonds change.
reactant: Any of the starting molecules in a chemical reaction.
product: Any one of the transformed molecules that result from a chemical reaction.
2.3: Water: The Medium of Life
Water is a polar molecule
polar: A molecule that has regions of positive and negative charge; readily dissolve in water
(ex: salt)
hydrophilic: “Water loving”; describes a class of molecules with which water can undergo
hydrogen bonding.
hydrophobic: “Water fearing”; describes a class of molecules poorly able to undergo hydrogen
bonding with water.
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Solvent: A liquid capable of dissolving a substance; dissolves a solute in a solution
aqueous: Watery.
Nonpolar: Describes compounds that do not have regions of positive and negative charge
(partial charges); combine poorly with water (ex: oil)
hydrophobic effect: The exclusion of nonpolar molecules by polar molecules, which drives
biological processes such as the formation of cell membranes and the folding of proteins.
Hydrogen bonds give water many unusual properties
cohesion: Attraction between molecules; one consequence of cohesion is high surface tension;
hydrogen bonding gives water this property
Hydrogen bonds allow water to have cohesion (water sticks together, high surface
tension, water travels up plants) and high heat capacity (stronger bonds/resistant to
temp changes)
pH is a measure of the concentration of protons in a solution
pH of a solution consists of proton concentration: pH = log [H+]
pH ranges 0 to 14; being logarhitmic, [H+] changes 10x with just 1 unit of difference in
pH
Acidic: Describes a solution in which the concentration of protons is higher than that of
hydroxide ions (the pH is lower than 7).
Neutral: pH is 7; concentrations of protons (H+) and hydroxide ions (OH-) are equal
Basic: Describes a solution in which the concentration of protons is lower than that of
hydroxide ions (the pH is higher than 7).
Acid: molecule that releases a proton (H+)
Base: a molecule that accepts a proton in aqueous solution
2.4: Carbon: Life’s Chemical Backbone
organic molecule: A carbon-containing molecule.
Carbon atoms form four covalent bonds
Form tetrahedtral; single bonds can rotate freely
Contribute to structural diversity of organic molecules
Carbon-based molecules are structurally and functionally diverse
Can link together to form chains (branched or not), rings, etc.
Simplest chain, ethane (C2H6)
Can also form double bonds (double bonds cannot rotate) that appear on chains and rings
Isomers: Molecules that have the same chemical formula but different structures.
Scale and Approximation
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