Examples of ion in the following topics:
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- Chemiosmosis is the movement of ions across a selectively permeable membrane, down their electrochemical gradient.
- The uneven distribution of H+ ions across the membrane establishes both concentration and electrical gradients (thus, an electrochemical gradient) owing to the hydrogen ions' positive charge and their aggregation on one side of the membrane.
- If the membrane were open to diffusion by the hydrogen ions, the ions would tend to spontaneously diffuse back across into the matrix, driven by their electrochemical gradient.
- However, many ions cannot diffuse through the nonpolar regions of phospholipid membranes without the aid of ion channels.
- At the end of the pathway, the electrons are used to reduce an oxygen molecule to oxygen ions.
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- It is now referred to as a sodium ion.
- It is now referred to as a chloride ion.
- Both ions now satisfy the octet rule and have complete outer shells.
- Ionic bonds are formed between ions with opposite charges.
- For instance, positively charged sodium ions and negatively charged chloride ions bond together to form sodium chloride, or table salt, a crystalline molecule with zero net charge.
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- To enter or exit the neuron, ions must pass through special proteins called ion channels that span the membrane.
- Some ion channels need to be activated in order to open and allow ions to pass into or out of the cell.
- Ion channels that change their structure in response to voltage changes are called voltage-gated ion channels.
- Voltage-gated ion channels regulate the relative concentrations of different ions inside and outside the cell.
- Recall that sodium-potassium pumps bring two K+ ions into the cell while removing three Na+ ions per ATP consumed.
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- Hydrogen ions are spontaneously generated in pure water by the dissociation (ionization) of a small percentage of water molecules into equal numbers of hydrogen (H+) ions and hydroxide (OH-) ions.
- The hydroxide ions remain in solution because of their hydrogen bonds with other water molecules; the hydrogen ions, consisting of naked protons, are immediately attracted to un-ionized water molecules and form hydronium ions (H30+).
- The concentration of hydrogen ions dissociating from pure water is 1 × 10-7 moles H+ ions per liter of water.
- A base provides either hydroxide ions (OH–) or other negatively-charged ions that react with hydrogen ions in solution, thereby reducing the concentration of H+ and raising the pH.
- When bicarbonate ions combine with free hydrogen ions and become carbonic acid, hydrogen ions are removed, moderating pH changes.
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- Ions cannot diffuse passively through membranes; instead, their concentrations are regulated by facilitated diffusion and active transport.
- Salt and other compounds that dissociate into their component ions are called electrolytes.
- In water, sodium chloride (NaCl) dissociates into the sodium ion (Na+) and the chloride ion (Cl–).
- The mechanisms that transport ions across membranes are facilitated diffusion and active transport.
- Active transport requires energy in the form of ATP conversion, carrier proteins, or pumps in order to move ions against the concentration gradient.
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- Water's polarity makes it an excellent solvent for other polar molecules and ions.
- Dissociation occurs when atoms or groups of atoms break off from molecules and form ions.
- Consider table salt (NaCl, or sodium chloride): when NaCl crystals are added to water, the molecules of NaCl dissociate into Na+ and Cl– ions, and spheres of hydration form around the ions.
- The positively-charged sodium ion is surrounded by the partially-negative charge of the water molecule's oxygen; the negatively-charged chloride ion is surrounded by the partially-positive charge of the hydrogen in the water molecule.
- When table salt (NaCl) is mixed in water, spheres of hydration form around the ions.
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- Three sodium ions bind to the protein.
- The shape change increases the carrier's affinity for potassium ions, and two such ions attach to the protein.
- The protein now has a higher affinity for sodium ions, and the process starts again.
- At this point, there are more sodium ions outside of the cell than inside and more potassium ions inside than out.
- For every three ions of sodium that move out, two ions of potassium move in.
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- A uniporter carries one specific ion or molecule.
- A symporter carries two different ions or molecules, both in the same direction.
- Some examples of pumps for active transport are Na+-K+ ATPase, which carries sodium and potassium ions, and H+-K+ ATPase, which carries hydrogen and potassium ions.
- A uniporter carries one molecule or ion.
- A symporter carries two different molecules or ions, both in the same direction.
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- The mEq/L is the ion concentration, in millimoles, multiplied by the number of electrical charges on the ion.
- The milliequivalent unit incorporates both the ion concentration and the charge on the ions.
- Thus, for ions that have a charge of one, such as sodium (Na+), one milliequivalent is equal to one millimole.
- For ions that have a charge of two, such as calcium (Ca2+), one milliequivalent is equal to 0.5 millimoles.
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- Secondary active transport brings sodium ions, and possibly other compounds, into the cell.
- As sodium ion concentrations build outside the plasma membrane because of the action of the primary active transport process, an electrochemical gradient is created.
- If a channel protein exists and is open, the sodium ions will be pulled through the membrane.
- This secondary process is also used to store high-energy hydrogen ions in the mitochondria of plant and animal cells for the production of ATP.
- The potential energy that accumulates in the stored hydrogen ions is translated into kinetic energy as the ions surge through the channel protein ATP synthase, and that energy is used to convert ADP into ATP.