Biochemistry Flashcards
(31 cards)
Ground state
All the electrons in an atom are in the lowest available energy levels
Excited state
When an atom absorbs energy, it’s electrons move to a higher energy level
Isotopes
Atoms of one element that vary only in the number of neutrons in the nucleus; all isotopes of the same element are identical because they have the same number of electrons in the same configuration
Half life
Decay rate of radioactive isotopes
Radioisotope
Radioactive isotopes
Radioactive iodine
Can be used to diagnose and treat certain diseases of the thyroid gland
Tracer
Ex. Radioactive carbon
Can be incorporated into a molecule and used to trace the path of carbon dioxide in a metabolic pathway
Bond
Formed when two atomic nuclei attract the same electron/s
Energy is released when a bond is formed because atoms acquire a more stable configuration by bonding. They form a completed outer shell. Energy must be supplied to break a bond
Ionic bond
Result from the transfer of electrons
Anion
An atom that gains electrons (a negative ion)
Cation
An atom that loses an electron (a positive ion)
Na+, Ca++, and CI- ions are all necessary for normal nerve function
Covalent bonds
Form when atoms share electrons
Molecule
The resulting structure of a covalent bond
Nonpolar bond
When electrons are shared equally between two identical atoms; this is the type of bond found in diatomic molecules, such as H2 and O2
Polar covalent bond
When electrons are shared unequally; this is the case between any two different atoms such as between atoms of carbon and oxygen in CO2
Hydrophilic
“Water loving”; polar substances dissolve in water, known as the “universal solvent”
Hydrophobic
“Water hating”; applies to nonpolar substances, which will dissolve in lipids; since the plasma membrane is a phospholipid bilayer, only nonpolar substances can dissolve through it; large polar molecules must travel across a membrane in special hydrophilic (protein) channels
Water
Asymmetrical and highly polar; positive hydrogen, negative oxygen; the strong hydrogen attraction that water molecules have for each other is responsible for the special characteristics of water that are important for life on earth; high specific heat/heat of vaporization; strong cohesion tension
Hydrogen bonding
The positive hydrogen of one molecule is attracted to the negative oxygen of an adjacent molecule
Transpirational-pull cohesion tension
The means by which water moves up a tall tree from the roots to the leaves without the expenditure of energy; as one molecule of water is lost from the leaf by transpiration, another molecule is drawn in at the roots
Capillary action
Results from the combined forces of cohesion and adhesion
Spring overturn
When floating ice melts in the spring, becomes denser and sinks to the bottom of the lake, causing water to circulate throughout the lake
Oxygen from the surface is returned to the depths and nutrients released by the activities of bottom dwelling bacteria during winter are carried to the upper layers of the lake
pH
A measure of the acidity and alkalinity of a solution; pH less than 7 is acidic, greater than 7 is basic, 7 is neutral
The value of the lH is the negative log of the hydrogen ion concentration in moles per liter
Buffers
How biological systems regulate their pH; works by either absorbing excess hydrogen ions or donating hydrogen ions when there are too few; the most important buffer in human blood is the bicarbonate ion
