Cytoplasm /histology Gartner, Hiatt/ Page 11-20

Front 1

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

Front 2

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

Front 3

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

Front 4

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

Front 5

Phospholipid molecule is said to be amphipathic because:

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It is composed of hydrophilic head and hydrophobic tail.

Front 6

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)

Front 8

Structure composed of carbohydrate chains which serve as cells coat is:

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GLYCOCALYX

Front 9

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)

Front 10

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