Key terms Flashcards
bacteriorhodopsin
Pigmented protein found in abundance in the plasma
membrane of the salt-loving archaeon Halobacterium
halobium; pumps protons out of the cell, fueled by light
energy.
cell cortex
Specialized layer of cytoplasm on the inner face of the
plasma membrane.
cholesterol
Short, rigid lipid molecule present in large amounts in the
plasma membranes of animal cells, where it makes the lipid
bilayer less flexible.
detergent
Soapy substance used to solubilize lipids and membrane
proteins.
fat droplet
Large cluster of hydrophobic fats or oils that forms inside
the cells.
glycocalyx
Protective layer of carbohydrates on the outside surface
of the plasma membrane formed by the sugar residues of
membrane glycoproteins, proteoglycans, and glycolipids.
lipid bilayer
Thin pair of closely juxtaposed sheets, composed mainly of phospholipid molecules, that forms the structural basis for
all cell membranes.
membrane domain
Functionally and structurally specialized region in the membrane of a cell or organelle; typically characterized by
the presence of specific proteins.
membrane protein
Voltage difference across a membrane due to a slight
excess of positive ions on one side and of negative ions on
the other.
phosphatidylcholine
phosphatidylcholine
Common phospholipid present in abundance in most cell
membranes; uses choline attached to a phosphate as its
head group.
phospholipid
A major type of lipid molecule in many cell
membranes. Generally composed of two fatty
acid tails linked to one of a variety of phosphatecontaining
polar groups.
plasma membrane
The protein-containing lipid bilayer that surrounds a living
cell.
saturated
Describes an organic molecule that contains a full
complement of hydrogen; in other words, no double or
triple carbon–carbon bonds.
unsaturated
Describes an organic molecule that contains one or more
double or triple bonds between its carbon atoms.
action potential
Traveling wave of electrical excitation caused by rapid,
transient, self-propagating depolarization of the plasma
membrane in a neuron or other excitable cell; also called
a nerve impulse.
active transport
The movement of a solute across a membrane against its
electrochemical gradient; requires an input of energy, such
as that provided by ATP hydrolysis.
antiport
Type of coupled transporter that transfers two different
ions or small molecules across a membrane in opposite
directions, either simultaneously or in sequence.
axon
Long, thin extension that conducts electrical signals away
from a nerve cell body toward remote target cells.
Ca2+ pump
Enzyme that phosphorylates target proteins in response to
an increase in Ca2+ ion concentration through its interaction
with the Ca2+-binding protein calmodulin.
channel
A protein that forms a hydrophilic pore
across a membrane, through which
selected small molecules or ions can
passively diffuse.
dendrite
Short, branching structure that extends from the surface of
a nerve cell and receives signals from other neurons.
depolarization
A shift in the membrane potential, making it less negative
on the inside of the cell.
electrochemical gradient
Driving force that determines which way an ion will move
across a membrane; consists of the combined influence
of the ion’s concentration gradient and the membrane
potential.
gradient-driven pump
A protein that uses energy stored in the electrochemical
gradient of ions to actively transport a solute across a
membrane.