electrochemical gradient

A component of every biological cell, the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. It separates a cell's interior from its surroundings and controls what moves in and out. Cell surface membranes often contain receptor proteins and cell adhesion proteins. There are also other proteins with a variety of functions. These membrane proteins are important for the regulation of cel ...

Including:

• Cell membrane - A fluid mosaic
• Cell membrane - Detailed structure
• Cell membrane - Transport across membranes
• Cell membrane - Passive transport
• Cell membrane - Active transport

Read more here: » Cell membrane: Encyclopedia - Cell membrane

Active transport is the mediated transport of biochemicals, and other atomic/molecular substances, across membranes. Unlike passive transport, this process requires chemical energy. In this form of transport, molecules move against either an electrical or concentration gradient (collectively termed an electrochemical gradient). This is achieved by either altering the affinity of the binding site or altering the rate at which the protein changes conformations. Active transport - Types. There are two main typ ...

Including:

• Active transport - Types
• Active transport - Primary
• Active transport - Secondary

Read more here: » Active transport: Encyclopedia - Active transport

Cellular respiration is the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. Oxidation of organic material—in a bonfire, for example—is an exothermic reaction that releases a large amount of energy rather quickly. The equation for the oxidation of glucose is: C6H12O6 + 6O2 → 6CO2 + 6HIncluding:

• Cellular respiration - Aerobic respiration
• Cellular respiration - Glycolysis
• Cellular respiration - Oxidative decarboxylation
• Cellular respiration - Krebs cycle/Citric Acid cycle
• Cellular respiration - Oxidative phosphorylation
• Cellular respiration - Theoretical yields
• Cellular respiration - Anaerobic respiration

Read more here: » Cellular respiration: Encyclopedia - Cellular respiration

Activation of a photoreceptor cell is actually a hyperpolarization; when they are not being stimulated, rods and cones depolarize and release a neurotransmitter spontaneously, and activation of photopigments by light sends a signal by preventing this. Depolarization occurs due to the fact that in the dark, cells have a relatively high concentration of cyclic guanosine 3'-5' monophosphate (cGMP), which opens ion channels (largely sodium channels, though Calcium can enter through these channels as well). The positive charges of the ions that e ...

See also:

Rod cell, Rod cell - Response to light, Rod cell - Table, Rod cell - Reference

Read more here: » Rod cell: Encyclopedia II - Rod cell - Response to light

Aerobic respiration requires oxygen in order to generate energy. It is the preferred method of pyruvate breakdown from glycolysis and requires that pyruvate enter the mitochondrion to be fully oxidized by the Krebs cycle. The product of this process is energy in the form of ATP (Adenosine Triphosphate), by substrate-level phosphorylation, NADH and FADH2. The reducing potential of NADH and FADH2 is converted to more ATP via an electron transport chain with oxygen as the "terminal electron acceptor". Most of the ATP produced by cellular ...

See also:

Cellular respiration, Cellular respiration - Aerobic respiration, Cellular respiration - Glycolysis, Cellular respiration - Oxidative decarboxylation, Cellular respiration - Krebs cycle/Citric Acid cycle, Cellular respiration - Oxidative phosphorylation, Cellular respiration - Theoretical yields, Cellular respiration - Anaerobic respiration

Read more here: » Cellular respiration: Encyclopedia II - Cellular respiration - Aerobic respiration

When closed, sodium channels help to maintain a neuron's resting potential, and when open, they allow sodium ions to flow rapidly down their electrochemical gradient, thus depolarizing the neuron. Voltage-gated Na+ channels are probably genetically related to potassium and calcium channels; in fact, a change of two amino acids will cause the channel to behave as a calcium channel (Kandel, 2000, p. 164). ...

See also:

Sodium ion channel, Sodium ion channel - Voltage-gated sodium channels, Sodium ion channel - Structure and gating, Sodium ion channel - Impermeability to other ions, Sodium ion channel - Role in action potential, Sodium ion channel - Reference

Read more here: » Sodium ion channel: Encyclopedia II - Sodium ion channel - Voltage-gated sodium channels

Each muscle fiber consists of T-tubules which run perpendicularly (transversely) to the long axis of the fiber. As they are invaginations of the plasma membrane, each T-tubule is composed of a phospholipid bilayer in which are embedded a large number of L-type calcium channels. The T-tubule extends from the surface of the muscle fiber into its interior, effectively bringing the extracellular environment in close proximity ...

See also:

T-tubule, T-tubule - Structure, T-tubule - Excitation-contraction coupling, T-tubule - Detubulation

Read more here: » T-tubule: Encyclopedia II - T-tubule - Structure

Aerobic respiration requires oxygen in order to generate energy. It is the preferred method of pyruvate breakdown from glycolysis and requires that pyruvate enter the mitochondrion to be fully oxidised by the Krebs cycle. The product of this process is energy in the form of ATP (Adenosine Triphosphate), by substrate-level phosphorylation, NADH and FADH2. The reducing potential of NADH and FADH2 is converted to more ATP via an electron transport chain with oxygen as the "terminal electron acceptor". Most of the ATP produced by cellular ...

See also:

Cellular respiration, Cellular respiration - Aerobic respiration, Cellular respiration - Glycolysis, Cellular respiration - Oxidative decarboxylation, Cellular respiration - Krebs cycle/Citric Acid cycle, Cellular respiration - Oxidative phosphorylation, Cellular respiration - Theoretical yields, Cellular respiration - Anaerobic respiration

Read more here: » Cellular respiration: Encyclopedia II - Cellular respiration - Aerobic respiration

Phospholipid molecules in the cell membrane are "fluid," in the sense of free to diffuse and exhibit rapid lateral diffusion. Lipid rafts and caveolae are examples of cholesterol-enriched microdomains in the cell membrane. Many proteins are not free to diffuse. The cytoskeleton undergirds the cell membrane and provides anchoring points for integral membrane proteins. Anchoring restricts them to a particular cell face or surface – for example, the "apical" surface of epithelial cells that line the vertebrate gut – and limits how far they ...

See also:

Cell membrane, Cell membrane - A fluid mosaic, Cell membrane - Detailed structure, Cell membrane - Transport across membranes, Cell membrane - Passive transport, Cell membrane - Active transport

Read more here: » Cell membrane: Encyclopedia II - Cell membrane - Detailed structure

There are two main types, primary and secondary. In primary transport energy is directly coupled to movement of desired substance across a membrane, independent of any other species. Secondary transport concerns the diffusion of one species across a membrane to drive the transport of another. Active transport - Primary. Primary active transport directly uses energy to transport molecules across a membrane. Most of the enzymes that perform this type of transport are transmembrane ATPases. A primary ATPase universal to all cellular life is the sodium-potassium pump ...

See also:

Active transport, Active transport - Types, Active transport - Primary, Active transport - Secondary

Read more here: » Active transport: Encyclopedia II - Active transport - Types

T-tubules are the major sites for the coupling of excitation and contraction, which is the process whereby the spreading depolarization is converted into force production by muscle fibers. The L-type calcium channels in T-tubules activate in response to electrical stimulation; their opening allows calcium to flow down its electrochemical gradient and into the cell. Activation of the L-type channel also causes a mechanical interaction between it and calcium-release chann ...

See also:

T-tubule, T-tubule - Structure, T-tubule - Excitation-contraction coupling, T-tubule - Detubulation

Read more here: » T-tubule: Encyclopedia II - T-tubule - Excitation-contraction coupling

It is possible to physically and functionally uncouple T-tubules from the surface membrane using the technique known as detubulation. This relies on chemicals, such as dextran, that can initiate osmotic shock in the T-tubules when applied in high concentrations and then washed out. There is some evidence that heart failure precipitates the loss of the T-tubule network, again indicating their impor ...

See also:

T-tubule, T-tubule - Structure, T-tubule - Excitation-contraction coupling, T-tubule - Detubulation

Read more here: » T-tubule: Encyclopedia II - T-tubule - Detubulation

The basic composition and structure of the plasma membrane is the same as that of the membranes that surround organelles and other subcellular compartments. The foundation is a phospholipid bilayer, and the membrane as a whole is often described as a fluid mosaic – a two-dimensional fluid of freely diffusing lipids, dotted or embedded with proteins, which may function as channels or transporters across the membrane, or as receptors. The model was first proposed by S.J. Singer (1971) as a lipid protein model and extended to include the fluid character in a pub ...

See also:

Cell membrane, Cell membrane - A fluid mosaic, Cell membrane - Detailed structure, Cell membrane - Transport across membranes, Cell membrane - Passive transport, Cell membrane - Active transport

Read more here: » Cell membrane: Encyclopedia II - Cell membrane - A fluid mosaic

The yields in the table below are for one glucose and molecule being fully oxidised to carbon dioxide. It is assumed that all the reduced coenzymes are oxidised by the electron transport chain and used for oxidative phosphorylation. Although there is a theoretical yield 36 ATP molecules per glucose during cellular respiration, such conditions are generally not realized due to losses such as the cost of moving pyruvate (from glycolysis), phosphate and ADP (substrates for ATP syhthesis) into the mitochondria. All are actively transporte ...

See also:

Cellular respiration, Cellular respiration - Aerobic respiration, Cellular respiration - Glycolysis, Cellular respiration - Oxidative decarboxylation, Cellular respiration - Krebs cycle/Citric Acid cycle, Cellular respiration - Oxidative phosphorylation, Cellular respiration - Theoretical yields, Cellular respiration - Anaerobic respiration

Read more here: » Cellular respiration: Encyclopedia II - Cellular respiration - Theoretical yields