3.2 The Cell Surface Flashcards
plasma membrane
defines the boundaries of the cell, governs its interactions with other cells, and controls the passage of materials into and out of the cell
intracellular face
the side of the plasma membrane that faces the cytoplasm
extracellular face
the side of the plasma membrane that faces outward from the cell
molecular structure of the plasma membrane
98% lipids (75% phospholipids, 20% cholesterol molecules, 5% glycolipids) + 2% proteins
glycocalyx
carbohydrate coating on the cell surface with multiple functions
transmembrane proteins
proteins that pass completely through the phospholipid bilayer and either drift in the phospholipid film or are anchored to the cytoskeleton
peripheral proteins
proteins that adhere to either the inner or outer face of the membrane
receptors
surface proteins to which chemical signals bind for the purpose of cell communication
enzymes
carry out the final stages of starch and protein digestion in the small intestine, help produce second messengers, and break down hormones and other signaling molecules whose job is done
channel proteins
passages that allow water and hydrophilic solutes to move through the plasma membrane
leak channels
channels that are always open and allow materials to pass through continuously
gated channels
channels that open and close under different circumstances; play a role in the timing of nerve stimulation and muscle contraction
ligand-gated channels
channels that respond to chemical messengers
voltage-gated channels
channels that respond to changes in electrical potential across the plasma membrane
mechanically gated channels
channels that respond to physical stress on a cell, such as stretch or pressure
channelopathies
diseases caused by defects in channel proteins
carriers
transmembrane proteins that bind to glucose, electrolytes, and other solutes and transfer them to the other side of the membrane
pumps
carriers that consume ATP in the process of transferring solutes across the plasma membrane
cell-adhesion molecules
membrane proteins through which cells adhere to one another and to extracellular material
calcium channel blockers
a class of drugs that show the therapeutic relevance of understanding gated membrane channels
glycocalyx
a fuzzy coat external to the plasma membrane composed of the carbohydrate moieties of membrane glycolipids and glycoproteins that is chemically unique in each individual (except identical twins) and acts like an identification tag that enables the body to distinguish its own healthy cells from transplanted tissues, invading organisms, and diseased cells
microvilli
extensions of the plasma membrane that increase a cell’s surface area; best developed in cells specialized for absorption (e.g. epithelial cells of intestines and kidneys)
brush border
a fringe of microvilli on the apical surface of an epithelial cell, serving to enhance surface area and promote absorption
terminal web
a protein mesh to which microvilli are anchored by actin filaments
cilia
hairlike processes with functions include sense, balance, and fluid flow monitoring
ciliopathies
birth defects and hereditary diseases caused by defects in the development, structure, or function of the cilia
power stroke
movement of the cilium that pushes along mucus or other matter
recovery stroke
movement of the cilium that restores it to the upright position, ready to flex again
chloride pumps
pumps that produce a saline layer at the cell surface by pumping Cl- into the extracellular fluid so that cilia can beat freely
axoneme
the structural basis for ciliary movement, consisting of an array of thin protein cylinders called microtubules
basal body
peripheral microtubules anchoring the cilium
dynein arms
a motor protein on a microtubule
flagellum
beats in an undulating, snakelike, corkscrew fashion
pseudopod
cytoplasm-filled extensions of the cell that have different shapes and change continuously
