how do cells make direct contact?
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cells communicate via molecules they release and the receptors that recognize the molecules.  For example, hormone is one way a distant cells or tissue communicate with other tissue down the stream.  In addition, cell that are adjacent to each other will also communicate by biological molecules, that are not hormones.  For example, Interleukin molecules are use T cells to communicate with B cells within our immune system.\n\nin term of nerve cells, the neuron will have cell potential changes and the signal travels as a form of electric signnal all the way along the long axon.  then the signal terminal wih the release of molecules, such as the epinephrine or the acetylcholine.  these molecules bind to the receptor of the post-synatic neuron and pass the signal along to the next neurons.  \n\nsometimes, a cell will conduct self signaling by release a molecules and the molecules bind to a receptor on the cell itself and generate a signal that re-transmit back to the cell.\n\nSignal transduction is another huge topic that is to difficult to discuss here.  basically, signal transduction mechanism happen in every cells, when the receptor binds to a protein/ molecule, it will change its configuration and chemical or physiological changes occur.  this changes cause many cascade events down the stream and allow the cells to do a lot of things, even turning on or off a gene expression.
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CELL MEMBRANE IS THE BOUNDARY BETWEEN IT'S CELL AND IT ENVIRONMENT
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Around the cell. It's what holds all the squishy bits in (cytoplasm etc.)
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Light pushes electrons outs of the atoms in the cell making electricity
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G'day Joanne F,\n\nThank you for your question.\n\nIt is essential if you are studying medicine to have a good understanding of how cells and tissues work. It is also useful to know how particular cells such as blood cells work.\n\nRegards
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A model of a cell is a good choice.
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Just a word of confirmation- Neurons are not the only players in transmission- There is increasing evidence that glial cells can transmit is "spreading waves" by depolarization.
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nerve cells(neurons) carry electrical signals through the body through the use of dentrites and axons, dentrites usually recieve signals and axons send signals although dentrites can send signals too, the cells relay messages between the brain and muscles and tell the muscles to move.\n\nWhen sending a message neurons send the eletrical signal through the axon into a synapse, then the signal goes into the dentrites of another neuron
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In an animal cell, cytokinesis is accomplished by a ring of protein that tightens and eventually splits the cell into two.  In plants, cytokinesis is accomplished by small packets of membrane (vesicles) that fuse in the midline and deposit new material to make a new cell plate (cell wall).
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They work through signal transduction.
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Dialysis tubing can come in various pore sizes that allow selective passage of materials. This is like a cell membrane that is also selective, but not really in terms of the size of the material. It has to do with the polarity (cell membrane is bipolar-has polar head with long, non-polar tail, but two chains of this with non-polar ends facing inward on the membrane and polar heads facing the outside of the membrane). Polar molecules (such as Na+ or K+) need to go through membrane-bound protein channels or receptors.
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some cells to take in more. Cell permiablility.\n\nhttp://www.answers.com/topic/cell-permeability
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All cells are semipermeable and depending on what passes into the cell, determines how the membrane responds to each substance. Glucose moves across the membrane, as do sodium and potassium.
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Cell membrane, or phospholipid bi-layer.
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Sure, some cells are bound to get stuck on the place once in your mouth.
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1. I guess You think about the nexuses. Its a metabolic and ionic connection of cells in form of ionic channels (built by proteins called conexones or conexone proteins).It provides rapid transport of membrane polarization changes. Its a form of electric synapses.\n2.I guess You think about the lysosomes. They're created by Golgi's Apart ('Trans" side).Lysosomic enzymes are created by Rough Endoplasmic Reticulum and GA. Lysosomical endoenvironment's pH is about 5. Function- to connect with endosomes, phagosomes and autophagosomes and to catalyze and guide analysis reaction (some kinds of digestive reactions).
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You're probably referring to the plasma membrane. The interior is hydrophobic, while the exterior is hydrophillic. The phospholipids can translocate horizontally within the bilayer, but can't cross from one layer to the other. So, the membrane behaves like a fluid.  See MIT's website for more info. the link is below