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20 Cards in this Set
- Front
- Back
Protoplasm- the living substance of the cell is subdivided into two compartments:
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*cytoplasm-extending from the plasma membrane to the nuclear envelope
*karyoplasm-substance forming the contents of the nucleus |
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Main functions of plasmalemma (cell membrane) are:
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*maintaining the structural integrity of the cell
*selective permeability *regulating cell-cell interactions *establishing transport systems for specific molecules *transducing extracellular physical or chemical signals into intracellular events |
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Leaflet is composed of:
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single layer of phospholipids and associated proteins (1:1 proportion by weight)
! myelin sheaths the lipid component outweighs the protein component by ratio of 4:1 |
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Each phospholipid molecule of the lipid bilayer is composed of:
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POLAR HEAD: *nitrogenous compound
*phosphote brigde *glycerol NONPOLAR TAIL: * saturated fatty acid |
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Phospholipid molecule is said to be amphipathic because:
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It is composed of hydrophilic head and hydrophobic tail.
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Membrane structure referees to FLUID MOSAIC MODEL because...
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....integral membrane proteins have the ability to float like icebergs in the sea of phospholipids.
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What is the P-face and what is the E-face?
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P-face- the outer surface of the inner leaflet (closer to the protoplasm)
E-face- inner surface of the outer leaflet (closer to the extracellular space) |
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Structure composed of carbohydrate chains which serve as cells coat is:
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GLYCOCALYX
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The most important function of the glycocalyx is:
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Protection of the cell from interaction with inappropriate proteins (from chemical injury and from physical injury)
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Which structures facilitate the movement of aqueous molecules and ions across the plasmalemma?
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Membrane Transport Proteins
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What molecules can move across membrane by SIMPLE DIFFUSION down their concentration gradient?
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*nonpolar: benzene, oxygen, nitrogen
*uncharged polar: water, glycerol |
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They may be gated or ungated, the are incapable of transporting substances against a concentration gradient....
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CHANNEL PROTEINS
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Example of localization of mechanically-gated channels:
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*hair cells of the inner ear
(they possess STEREOCILIA that are embedded in a matrix known as the TECTORIAL MEMBRANE) |
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Example of the voltage-gated channels:
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*most common in nerve cells (depolarization in the transmission of the nerve impulse)
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Example of G-protein-gated ion channels:
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*muscarinic acetyloholine receptors of cardiac muscle cells
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Ligands signaling molecules may differentiate according to the place to which they bind,....
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*ligands that bind to cell-surface receptors usually are POLAR molecules
*those thet bind to intracellular receptors are HYDROPHOBIC |
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Signaling molecules which cannot penetrate the cell membrane are:
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ACETYLOCHOLINE (hydrophilic molecules)
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Steroid hormones (hydrophobic) or small nonpolar molecules nitric oxide (NO)....
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have the ability to diffuse through the lipid bilayer
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Difference in life span between most hydrophilic and hydrophobic ligands:
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Hydrophilic l. have a very short life span (milliseconds) whereas e.x steroid hormones last for extended time periods (days)
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AQUAPORINS-
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special protein channels which help water to pass hydrophobic core of the phospholipids
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