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EB 2240 Exam II

Membranes (Cell Potential)

QuestionAnswer
what is the approximate thickness of a cell membrane? 8 nm (between 6nm and 10nm)
What is the interface of two environments? A membrane
What are membranes mainly made up of? proteins and lipids
where do carbohydrates connect to the membrane? attach to proteins and lipids
T or F: Membrane lipids have both hydrophilic and hydrophobic characteristics true
T or F: lipids with dual nature can form bimolecular sheets in water environment true
What are other characteristics of the membrane? Insulators; barriers to the flow of polar molecules; non-covalent assemblies; fluid mosaic model
T or F: membrane faces are symmetrical False: they are asymmetric
What functions does membrane potential play a key role in? Transport; energy conversion; excitability
What mediates the distinctive functions of membranes? Membrane Proteins: serve as pumps, channels, receptors, energy transducers, and enzymes
What are closed vesicles are uniform in size? Liposomes or lipid vesicles
How are liposomes/lipid vesicles formed? Sonication (high frequency sound waves)
What are Liposomes used for? contain DNA or Drugs for delivery!
what is a specific kind of pump/channel that facilitate the movement of molecules across a membrane Transporters
What determines the Cell Characteristics? Transporters
What two factors decide if a small molecule will cross or not? concentration gradient and the molecule's solubility
what is the difference in electrical potential between the interior and exterior of a biological cell? Membrane potential
What are typical values of membrane potential range? -60mV to -80 mV (sometimes -40mV to -80mV)
T or F: Virtually all eukaryotic cells (including plants, animals, fungi) maintain a non-zero potential True
What is the general resting membrane potential of the cell interior? Negative!
What is the general resting membrane potential of the cell exterior? Positive!
What are the 2 basic functions of membrane potential? It allows a cell to function as a battery and it is used for transmitting signals
What are the two types of transmembrane proteins that let the transmitting of signals? Ion Transporter/Pump and Ion Channels
what does the Na+/K+ pump do? Uses ATP to pump 3Na+ out and 2K+ in
What allows the Na+ to get back into the cell? Leak channels (that are normally closed during resting potential of the cell)
What are the concentration gradients that the pump establishes? Na+ conc gradient (high outside) and K+ conc. gradient (high outside)
How long does the Action Potential signal take to cycle? 10 miliseconds
What is the ion that determines the so-called "resting" membrane potential of the cell? K+
T or F: Other ions do not contribute in more minor ways to establish resting potential False. They do contribute to resting potential
What causes the Na+ channels to open? A stimulus
T or F: the opening of the Na+ channels does not change the interior potential False; it is sufficient to drive the interior potential from -70mV to -55mV
What causes the membrane potential to be driven to a positive voltage on the interior; and what is this process called? Depolarization: the influx of Na+ drives the cell membrane to about +30mV
What happens after the cell is positive on the interior and the Na+ gates close? K+ channels open and K+ ions ruse out of the cell
Describe repolarization? Na+/K+ pump restores interior
What is the point of Hyperpolarization? stimulus will complete and the cell is recalibrated for a new stimulus (reaches -90mV)
T or F: at resting potential Na+ is concentrated outside the cell True
T or F: pump pushed 2K+in and 3Na+ out True
T or F: leak channels for Na+ are always open False, they are closed during the cell's resting position
Created by: savelae
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