Biology SAT II E/M
electrons are in the ground state when...
Electrons are in the lowest available energy level
electrons are in the excited state when...
Electrons move to higher energy levels when atoms absorb energy
Atoms of one element that vary only in the number of NEUTRONS in the nucleus
Isotopes that are radioactive (eg Carbon-14)
The nuclei of radioisotopes emit particles and decay at the rate known as a...
When two atomic nuclei attract the same electrons...
a bond is formed
Energy is released when...
bonds are formed
To break a bond, energy must be...
supplied or absorbed
Atoms bond to achieve...
There are two main types of bonds...
ionic and covalent
Atoms are stable when they have a...
completed outer shell
When electrons are transferred, what forms?
an ionic bond
An atom that gains electrons is an...
anion or negative ion
An atom that loses an electron is a...
cation or positive ion
Ions are necessary for...
normal cell, tissue, and organ function
Covalent bonds form when...
atoms share electrons
Atoms bonded together with covalent bonds are called...
Two atoms sharing one pair of electrons
a single covalent bond
Two atoms sharing two pairs of electrons
a double covalent bond
Two atoms sharing three pairs of electrons
a triple covalent bond
There are two types of covalent bonds...
nonpolar and polar
Unbalanced molecules are...
Balanced molecules are...
The negative end of one polar molecule attracts the...
positive end of another polar molecule
H20 is a ____ molecule
polar or unbalanced
What keeps the two strands of DNA bonded together, forming a double helix, and causes water molecules to stick together?
The attractions between nonpolar molecules are...
Polar substances ______ in water
Nonpolar substances _____ in water
don't dissolve in water
dissolve in water
Water has a ____ specific heat, which means it ____
high, absorbs heat and resists temperature changes
Water has a ____ vaporization heat, which means it needs ____ heat for evaporation
high, a lot
Water has ____ adhesion properties
Water dissolves all _____ and ____ substances
polar and ionic
Water exhibits ___ cohesion tension, which means...
high, the molecules of water stick together
Anything with a pH of less than 7 is
Anything with a pH value greater than 7 is
alkaline or basic
A solution of a pH 1 is ___ times more acidic than a solution of a pH 2
Organic compounds are compounds that contain...
The four classes of organic compounds are...
carbohydrates, lipids, proteins, and nucleic acids
Carbohydrates consist of 3 elements:
carbon, hydrogen, and oxygen
The 3 classes of carbohydrates are:
monosaccharides, disaccharides, and polysaccharides
All monosaccharides have a chemical formula of
Glucose, galactose, and fructose are...
Compounds with the same molecular formula with different structures, and physical and chemical properties
All disaccharides have the chemical formula:
The breakdown of a compound
The opposite of dehydration synthesis
Cellulose, starch, chitin, and glycogen are:
Fats, oils, and waxes are:
A hydrocarbon chain with a carboxyl group at one end
Fatty acids exist in two varieties:
saturated and unsaturated
saturated fats come from
Saturated fats are ___ at room temperature
Butter is a
Unsaturated fatty acids are extracted from
Unsaturated fatty acids are ___ at room temperature
Unsaturated fatty acids have at least one
double bond between carbon atoms in the hydrocarbon chain
Unsaturated fatty acids have ___ hydrogen atoms than saturated fats
Lipids are used for
energy storage, structure (cell membrane), and endocrine (hormones)
Polymers or polypeptides of repeating units called amino acids joined by peptide bonds
A carboxyl group, amine groups, and variable ("R") attatched to a central carbon atom
Proteins are complex macromolecules responsible for...
growth and repair
proteins consist of the elements
S P C O H N
there are ___ amino acids
enzymes membrane channels hormones
the sequence of amino acids that make up the protein chain