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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?

cell adhesion
immunity to infection
defense against cancer
embryonic development
transplant compatibility


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?

Hairlike processes
-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

Saline Layer:
-chloride pumps pump Cl- into ECF
-Na+ and H2O follows
-Cilia beat freely in saline layer


What is Cystic Fibrosis?

Hereditary disease in which cells make chloride pumps, but fail to install them in the plasma membrane

-chloride pumps fail to create adequate saline layer on cell surface
-Thick mucus plugs pancreatic ducts and respiratory tract
-Inadequate digestion of nutrients and absorption of oxygen
-Chronic respiratory infections
-Life expectancy of 30