Summary
Summary Biol 105 Test 1 Study Guide
- Course
- Bio 105
- Institution
- Queens College
This is a comprehensive and detailed study guide on Test 1 for Biol 105. *Essential Study Material!! *For you, at a price that's fair enough!!
[Show more]
Content preview
Test 1 Study GuideCh 2: Small Molecules and the Chemistry of Life
- neutron: particle with no electric charge that may be found inside nucleus
- electron: negatively charged particle that surrounds nucleus
o less mass than a proton; approx. 0.0005 Da and can usually be ignored
o determines how atoms will combine with other atoms to form stable
associations
- proton: positively charged particle inside of nucleus
o Dalton: standard unit of measurement for the mass of a proton; single proton or
neutron has a mass of 1 dalton (Da) = 1.7 x 10-24 grams
- atom: tiny, electrically charged particle that forms matter; has volume and mass
o nucleus: dense, positively charged center of an atom
o generally, are electrically neutral; number of electrons = number of protons
- molecule: chemical substance composed of 2 or more atoms joined by covalent or ionic
bonds
- element: fundamental substance that contains only one kind of atom; atoms of each
element have characteristics that distinguish them from the atoms of other elements
o physical / chemical properties depend on number of particles in the atom
o isotope: differing forms of the same element; same number of protons in the
nuclei but different numbers of electrons
- orbital: region of space surrounding atomic nucleus where electron is found 90% of the
time; have characteristic shapes and orientations
o a given orbital can be occupied by a maximum of 2 electrons; any atom larger
than helium must have electrons in 2 or more orbitals
o filled in specific sequences in a series of electron shells – first shell (innermost, 1
orbital), second shell (4 orbitals, 8 electrons), additional shells (elements with
more than 10 electrons have 3+ electron shells)
o s orbital: spherical orbital contained by every electron shell
o p-orbital: dumbbell shaped orbital in the 2nd and subsequent shells
- covalent bond: chemical bond that forms when 2 atoms attain stable electron numbers
in their outermost shells by sharing 1 or more pairs of electrons
o each atom contributes one member of each electron pair
o strong, stable, and length/angle of each bond, with respect to other bonds, is
always the same for a given pair of elements
o shapes can change; long chains of atoms can rotate freely to alter structures to
fit other molecules
shapes of molecules contribute to biological functions
o multiple covalent bonds can occur
bond energies are higher
- electronegativity: tendency of an atom to attract electrons when it occurs as part of a
compound; attractive force an atomic nucleus exerts on electrons
, o depends on how many positive charges it has (atoms with more protons = more
positive = more attractive to electrons)
o depends on distance between nucleus and electron in outer valence shell; closer
the electrons are, the higher the electronegative pull
o fluorine is most electronegative, followed by oxygen (3.5); many organisms
exploit the electronegativity of oxygen (moving electrons between C and O atoms
powers living systems)
- polarity: refers to a molecule with separate and opposite electric charges at 2 ends
(poles)
o molecules are termed “polar” if they contain polar covalent bonds and if one
region is more polar than others; water is most prevalent example
o nonpolar covalent bonds: covalent bond between atoms that have equal sharing
of electrons; happens 2 atoms are close to one another in electronegativity
o polar covalent bonds: electrons are drawn to 1 nucleus more than the other,
resulting in unequal distribution of charge; typically happens when 2 atoms differ
in electronegativity by more than 0.4
o partial charges that result from polar covalent bonds produce polar molecules or
polar regions of large molecules, which influence interactions that those
molecules have with other polar molecules
- ionic bonds: form as a result of electrical attraction between ions bearing opposite
charges; electrostatic attraction between positively and negatively charged ions
o ions: electrically charged particles that form when at atom gains / loses 1 or
more electrons; usually stable and no more electrons are gained / lost
o can form bonds that result in stable compounds; in solids, the attractions are
stronger because ions are close together
o less strong than covalent bonds; can interact with polar molecules
salt dissolving in water
o cation: ion with 1 or more positive charges
Na+, Ca2+, H+, Mg2+, K+
o anion: negatively charged ion
Cl-
- hydrogen bonds: weak electrostatic bond which arises from attraction between slight
positive charge on a hydrogen atom and a slight negative charge on a nearby oxygen or
nitrogen atom
o not restricted to water molecules; can form between electronegative atoms in
one molecule and hydrogen atoms involved in polar covalent bonds in another /
the same molecule
o weaker than most ionic bonds due to partial charges; have strength in numbers
and can influence structure / properties of a substance
o heat will break hydrogen bonds and 3d structure of molecule will change
- hydrophobic interactions: bring together nonpolar molecules in the presence of a polar
substance (especially water); in water, these molecules aggregate with one another
rather than the water molecules and create weak chemical interactions between
, themselves; can form weak interactions with water, but those interactions are weaker
than the hydrogen bonds between water molecules
o hydrophilic: having an affinity for water; hydrophobic / nonpolar molecules are
more likely to associate with one another than water
o polar molecules can interact with other polar molecules through weak
attractions of hydrogen bonds (or interact with water = hydrophilic)
- van der Waals forces: weak attractions between atoms in close proximity, resulting from
the interaction of the electrons of one atom with the nucleus of another; this type of
attraction is about a fourth as strong as a hydrogen bond
o result from random variations in electron distribution in 1 molecule, which can
create opposite charge distributions in the adjacent molecule & a weak,
temporary positive or negative attraction
o occur in nonpolar and polar molecules
in nonpolar molecules, they can induce cohesion between molecules that
do not form ionic bonds or hydrogen bonds
o brief, weak but collectively can create substantial attraction
- chemical reaction: change in the composition or distribution of atoms of a substance,
with consequent alterations in properties
o occurs when moving atoms collide with sufficient energy to combine or change
bonding partners
- energy: capacity to do work or move matter against an opposing force
o capacity to accomplish change in physical and chemical systems
o chemical reactions do not create or destroy energy, but create changes in the
form of energy
- acid: release H+ in solution
o contain carboxyl group –COOH
o incomplete reaction = weak acid; ionization of weak acids in water is somewhat
reversible
o acids that fully ionize in solution are strong acids (HCl, H2SO4 sulfuric acid);
ionization of strong acids in water is virtually irreversible
o lower pH; solution with pH value of less than 7 is acidic and contains more H+
ions than OH- ions
- base: accept H+
o weak bases include bicarbonate ion (HCO3-), which can accept an H+ ion and
become carbonic acid (H2CO3), and ammonia (NH3), which can accept H+ and
become an ammonium ion (NH4+); ionization of weak bases is somewhat
reversible
o NaOH is a strong base; ionization of strong bases in water is virtually irreversible
o biological compounds that contain –NH2 (the amino group) are also bases; it
accepts H+
o water is a weak acid and a weak base
o solution with a pH value above 7 is basic
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller anyiamgeorge19. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $10.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
53340 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now