ATP

(noun)

A nucleotide that occurs in muscle tissue, and is used as a source of energy in cellular reactions, and in the synthesis of nucleic acids. ATP is the abbreviation for adenosine triphosphate.

Related Terms

Examples of ATP in the following topics:

  • ATP: Adenosine Triphosphate

    • Cells couple the exergonic reaction of ATP hydrolysis with endergonic reactions to harness the energy within the bonds of ATP.
    • Since ATP hydrolysis releases energy, ATP synthesis must require an input of free energy.
    • ATP is a highly unstable molecule.
    • ATP is the primary energy currency of the cell.
    • Explain the role of ATP as the currency of cellular energy

  • ATP in Metabolism

    • This repulsion makes the ADP and ATP molecules inherently unstable.
    • The energy from ATP can also be used to drive chemical reactions by coupling ATP hydrolysis with another reaction process in an enzyme.
    • In reactions where ATP is involved, ATP is one of the substrates and ADP is a product.
    • A + enzyme + ATP→[ A enzyme −P ] B + enzyme + ADP + phosphate ion
    • Compare the two methods by which cells utilize ATP for energy.

  • Food Energy and ATP

    • Adenosine triphosphate, or ATP, is the primary energy currency in cells.
    • ATP stores energy in phosphate ester bonds, releasing energy when the phosphodiester bonds are broken: ATP is converted to ADP and a phosphate group.
    • ATP is required for all cellular functions.
    • When the amount of ATP available is in excess of the body's requirements, the liver uses the excess ATP and excess glucose to produce molecules called glycogen (a polymeric form of glucose) that is stored in the liver and skeletal muscle cells.
    • ATP is the energy molecule of the cell.

  • Outcomes of Glycolysis

    • One glucose molecule produces four ATP, two NADH, and two pyruvate molecules during glycolysis.
    • Glycolysis starts with one molecule of glucose and ends with two pyruvate (pyruvic acid) molecules, a total of four ATP molecules, and two molecules of NADH .
    • Two ATP molecules were used in the first half of the pathway to prepare the six-carbon ring for cleavage, so the cell has a net gain of two ATP molecules and 2 NADH molecules for its use.
    • Instead, glycolysis is their sole source of ATP.
    • In this situation, the entire glycolysis pathway will continue to proceed, but only two ATP molecules will be made in the second half (instead of the usual four ATP molecules).

  • ATP and Muscle Contraction

    • ATP is critical for muscle contractions because it breaks the myosin-actin cross-bridge, freeing the myosin for the next contraction.
    • ATP is critical to prepare myosin for binding and to "recharge" the myosin.
    • ATP first binds to myosin, moving it to a high-energy state.
    • The ATP is hydrolyzed into ADP and inorganic phosphate (Pi) by the enzyme ATPase.
    • Therefore, without ATP, muscles would remain in their contracted state, rather than their relaxed state.

  • Chemiosmosis and Oxidative Phosphorylation

    • Chemiosmosis is used to generate 90 percent of the ATP made during aerobic glucose catabolism.
    • The production of ATP using the process of chemiosmosis in mitochondria is called oxidative phosphorylation.
    • The overall result of these reactions is the production of ATP from the energy of the electrons removed from hydrogen atoms.
    • In oxidative phosphorylation, the hydrogen ion gradient formed by the electron transport chain is used by ATP synthase to form ATP.
    • ATP synthase is a complex, molecular machine that uses a proton (H+) gradient to form ATP from ADP and inorganic phosphate (Pi).

  • ATP Yield

    • In a eukaryotic cell, the process of cellular respiration can metabolize one molecule of glucose into 30 to 32 ATP.
    • The number of ATP molecules generated via the catabolism of glucose can vary substantially.
    • ATP is the main source of energy in many living organisms.
    • Glycolysis on the left portion of this illustration can be seen to yield 2 ATP molecules, while the Electron Transport Chain portion at the upper right will yield the remaining 30-32 ATP molecules under the presence of oxygen.
    • Describe the origins of variability in the amount of ATP that is produced per molecule of glucose consumed

  • The Energy-Releasing Steps of Glycolysis

    • In the second half of glycolysis, energy is released in the form of 4 ATP molecules and 2 NADH molecules.
    • So far, glycolysis has cost the cell two ATP molecules and produced two small, three-carbon sugar molecules.
    • Both of these molecules will proceed through the second half of the pathway where sufficient energy will be extracted to pay back the two ATP molecules used as an initial investment while also producing a profit for the cell of two additional ATP molecules and two even higher-energy NADH molecules .
    • Note that the second phosphate group does not require another ATP molecule.
    • The second half of glycolysis involves phosphorylation without ATP investment (step 6) and produces two NADH and four ATP molecules per glucose.

  • Citric Acid Cycle

    • If ATP levels increase, the rate of this reaction decreases.
    • If ATP is in short supply, the rate increases.
    • This form produces ATP.
    • GTP is energetically equivalent to ATP; however, its use is more restricted.
    • One GTP or ATP is also made in each cycle.

  • Processes of the Light-Dependent Reactions

    • Protein complexes and pigment molecules work together to produce NADPH and ATP.
    • Cytochrome b6f complex and ATP synthase are also major protein complexes in the thylakoid membrane that work with the photosystems to create ATP and NADPH.
    • Cytochrome b6f and ATP synthase work together to create ATP.
    • The energy released by the hydrogen ion stream allows ATP synthase to attach a third phosphate group to ADP, which forms ATP .
    • ATP synthase uses this electrochemical gradient to make ATP.