Bio Exam 2

Lipid

A molecule that does not dissolve in water

Staturated

A hydrocarbon chain that contain only single bonds

Unstaturated

A hydrocardon chain that contain one or more double bonds.

Fat

A lipid comprised of three fatty acids—these are hydrocarbon chains with a COOH group on one end—attached to glycerol (a 3-carbon compound)

Steroid

A lipid containing a specific “four-fused-rings” structure

Phospholipid

A lipid that consists of 1) a hydrophillic “head” that includes a phosphate group and another polar group, and 2) a hydrophobic hydrocarbon tail

Amphipathic

A molecule having both a hydrophobic regoin and hydrophilic region

Cell (plasma) membrane

The boundary of every cell on Earth, made of a lipid bilayer with proteins and carbohydrates.

Oligosaccharide

A chain of around 6-10 sugars long.

Peripheral membrane protein

A protein found on the inner or outer surface of a cell membrane.

Integral membrane protein

A protein embedded, or integrated, into a cell membrane.

Transmembrane protein

A type of integral membrane protein that spans the lipid bilayer of a cell membrane.

Kinetic energy

The energy of motion.

Diffusion

Movement of ions or molecules from an area of higher concentration to an area of lower concentration

Entropy

The tendency of systems to reach a state of higher disorder or randomness

Osmosis

Movement of water across a membrane, from an area of higher concentration (low solute concentration) to an area of lower concentration (higher solute concentration)

Concentration Gradient

A difference in a substance’s concentration in space—usually across a cell membrane

Potential Energy

The energy of position

Facilitated Diffusion

Diffusion of substances across cell membranes through integral membrane proteins.

Passive Transport

Movement of ions or molecules that does not require input of energy; occurs down a gradient and is spontaneous because it increases entropy

Active Transport

Movement of ions or molecules that requires an input of energy; occurs against a gradient and is nonspontaneous because it decreases entropy

Channel Protein

An integral membrane protein that facilitates diffusion of a specfic molecule across a membrane by changing shape once the molecule binds to it.

Pump

An integral membrane protein that transports specific ions or molecules against their concentration gradient across a membrane; uses energy input

Carrier Protein

An integral membrane protein that facilitates diffusion of a specific molecule across a membrane by changing shape once the molecule binds to it

Membrane Voltage

In cells, an electrical potential created by a seperation of charge across a membrane. Also called a transmembrane potential or a membrane potential.

Electric Current

In cells, a flow of charge in the form of ions.

Concentration Gradient

A difference in the concentration of an ion or molecule in one area versus another, often across a cell membrane or organelle membrane. Substances move down their concentration gradients passively and spontaneously, via diffusion.

Electric potential gradient

A difference in charge carried by ions in one area versus another, almost always across a cell membrane or organelle membrane. Substances move down their electric potential gradients passively and spontaneously, toward unlike charges and away from like charges.

Electrochemical Gradient

The overall gradient across a cell membrane or organelle membrane, produced by differences in concentration of substances combined with differences in the distribution of charge.

Electrical Energy

Energy related to interactions among charged particles.

Thermal Energy

The energy of motion in ions and molecules, measured as temperature.

Potential Energy

Energy that is related to an object’s position

Chemical Reaction

Conversion of substances (ions or molecules) into other substances via breaking and forming chemical bonds.

Free Energy

The total energy available to do work—a combination of entropy and thermal potential energy.

Energetic Coupling

A phosphorylation reaction that makes a nonspontaneous reaction spontaneous, because it raises the free energy of the reactants.

Endergonic Reaction

One that results in an increase in free energy; another way of referring to a nonspontaneous reaction.

Exergonic Reaction

One that results in a decrease in free energy; another way of referring to a spontaneous reaction.

Activation Energy

The amount of energy required to get a chemical reaction through its transition state.

Enzyme

A protein that cataluzes a chemical reaction.

Active site

The place on an enzyme (or ribozyme) where a reaction is catalyzed.