Flashcards in Chapter 3.2 Deck (12)
What are Membrane Enzymes?
Enzymes in plasma membrane carry out final stages of starch and protein digestion in small intestine
Helps produce second messengers (cAMP)
break down chemical messengers and hormones whose job is done, stops excessive stimulation.
What are Ion Channels?*
Transmembrane proteins with pores that allow water and dissolved ions to pass through membrane.
-some constantly open
-some are grated-channels that open and close in response to stimuli
-Ligand (chemically) regulated gates
-Voltage - regulated gates
-mechanically regulated gates (stretch and pressure)
-Play an important role in the timing of nerve signals and muscle contraction
What do membrane carriers or pumps do?
Transmembrane proteins bind to glucose, electrolytes and other solutes.
-transfer them across membrane
-pumped consume ATP in the process
What are cell-Identity markers?
Glycoproteins contribute to the glycocalyx
-carbohydrate surface coating
-acts like a cell's "identification tag"
Enables our bodies to identify which cells belong to it and while are foreign invaders
What are Cell-Adhesion molecules?
Adhere cells to each other and to extracellular material
Cells do not grow or survive normally unless they are mechanically linked to the extracellular material
What is Glycocalyx?
Unique fuzzy coat external to the plasma membrane.
-carbohydrates moieties of membrane glycoproteins and glycolipids
-unique in everyone, but identical twins
What are the functions of Glycocalyx?
immunity to infection
defense against cancer
What are Microvilli?
Extension of membrane:
-serves to increase cell's surface area
-best developed in cells specialized in absorption
-gives 15-40 times more absorptive surface area
on some cells they are very dense and appear as a fringe "brush border"
-milking action of actin.
-Actin filaments shorten microvilli
-pushing absorbed contents down into cell
What are Cilia?
-Single nonmotile primary cilium found on nearly every cell
-Antenna for monitoring nearby conditions
-sensory in inner ear, retina, nasal cavity and kidney
What is Motile Cilia?
Respiratory tract, uterine tubes, ventricles of the brain, efferent ductules of testes
-beat in waves
-sweep substances across surface in same direction
-power strokes followed by recovery strokes
What is the Axoneme?
The core of the cilia that is structural basis for ciliary movement.
-Has 9+2 structure of microtubules
-9 pairs form basal body inside the cell membrane, anchors cilium
-Dynein Arms "crawls" up adjacent microtubule bending the cilia, uses energy from ATP
-chloride pumps pump Cl- into ECF
-Na+ and H2O follows
-Cilia beat freely in saline layer