phosphate

Examples of phosphate in the following topics:

• The Pentose Phosphate Shunt

  • The pentose phosphate pathway (PPP) converts glucose-6-phosphate into NADPH and pentoses (5-carbon sugars).
  • The first is the oxidative phase in which glucose-6-phosphate is converted to ribulose-5-phosphate.
  • Glucose 6-phosphate + 2 NADP+ + H2O → ribulose-5-phosphate + 2 NADPH + 2 H+ + CO2
  • Depending on the body's state, ribulose-5-phosphate can reversibly isomerize to ribose-5-phosphate.
  • Ribulose-5-phosphate can alternatively undergo a series of isomerizations as well as transaldolations and transketolations that result in the production of other pentose phosphates including fructose-6-phosphate, erythrose-4-phosphate, and glyceraldehyde-3-phosphate (both intermediates in glycolysis).

• The Phosphorus Cycle

  • Phosphorus occurs in nature as the phosphate ion (PO43−).
  • In addition to phosphate runoff as a result of human activity, natural surface runoff occurs when it is leached from phosphate-containing rock by weathering, thus sending phosphates into rivers, lakes, and the ocean.
  • The movement of phosphate from the ocean to the land and through the soil is extremely slow, with the average phosphate ion having an oceanic residence time between 20,000 and 100,000 years.
  • In nature, phosphorus exists as the phosphate ion (PO43−).
  • Phosphate dissolved in ocean water cycles into marine food webs.

• The Energy-Requiring Steps of Glycolysis

  • Hexokinase phosphorylates glucose using ATP as the source of the phosphate, producing glucose-6-phosphate, a more reactive form of glucose.
  • In the second step of glycolysis, an isomerase converts glucose-6-phosphate into one of its isomers, fructose-6-phosphate.
  • A second ATP molecule donates a high-energy phosphate to fructose-6-phosphate, producing fructose-1,6-bisphosphate.
  • The fourth step in glycolysis employs an enzyme, aldolase, to cleave 1,6-bisphosphate into two three-carbon isomers: dihydroxyacetone-phosphate and glyceraldehyde-3-phosphate.
  • In the fifth step, an isomerase transforms the dihydroxyacetone-phosphate into its isomer, glyceraldehyde-3-phosphate.

• ATP in Metabolism

  • The addition of a second phosphate group to this core molecule results in the formation of adenosine diphosphate (ADP); the addition of a third phosphate group forms adenosine triphosphate (ATP).
  • The addition of a phosphate group to a molecule requires energy.
  • Phosphorylation refers to the addition of the phosphate (~P).
  • A + enzyme + ATP→[ A enzyme −P ] B + enzyme + ADP + phosphate ion
  • In phosphorylation reactions, the gamma phosphate of ATP is attached to a protein.

• Phosphorus Compounds

  • For this purpose, phosphate-containing minerals are converted to phosphoric acid.
  • Inorganic phosphorus in the form of the phosphate PO43− is required for all known forms of life.
  • As such, phosphate salts are used as fertilizers to aid plant growth.
  • Calcium phosphate salts help to harden bones.
  • DNA strands have a phosphate-deoxyribose backbone.

• Anion Regulation

  • Phosphate is present in the body in three ionic forms: H2PO4−, HPO42−, and PO43−.
  • Phosphate is useful in animal cells as a buffering agent, and the most common form is HPO2−4.
  • Bone and teeth bind up 85 percent of the body's phosphate as part of calcium-phosphate salts.
  • In the face of phosphate depletion, the kidneys usually conserve phosphate, but during starvation, this conservation is impaired greatly.
  • Additionally, because phosphate is a major constituent of the ICF, any significant destruction of cells can result in dumping of phosphate into the ECF.

• The DNA Double Helix

  • The DNA double helix looks like a twisted staircase, with the sugar and phosphate backbone surrounding complementary nitrogen bases.
  • DNA has a double-helix structure, with sugar and phosphate on the outside of the helix, forming the sugar-phosphate backbone of the DNA.
  • The phosphate backbone (indicated by the curvy lines) is on the outside, and the bases are on the inside.
  • The phosphate backbone is located on the outside, and the bases are in the middle.

• Regulation of the Calvin Cycle

  • The 3-PG molecules synthesized in phase 1 are reduced to glyceraldehyde-3-phosphate (G3P).
  • The fructose-1,6-bisphosphate formed in phase 2 is then converted into fructose-6-phosphate.
  • 2) Aldolase and fructose-1,6-bisphosphatase: converts G3P and DHAP into fructose 6-phosphate
  • 3) Transketolase: removes two carbon molecules in fructose 6-phosphate to produce erythrose 4-phosphate (E4P); the two removed carbons are added to G3P to produce xylulose-5-phosphate (Xu5P)
  • 6) Transketolase: removes two carbons from S7P and two carbons are transferred to one of the G3P molecules producing ribose-5-phosphate (R5P)and another Xu5P

• The Structure and Sequence of DNA

  • The components of the nucleotide used in DNA synthesis are a nitrogenous base, a deoxyribose, and a phosphate group .
  • Each nucleotide is made up of a sugar, a phosphate group, and a nitrogenous base.
  • In their mononucleotide form, nucleotides can have one, two , or three phosphates attached to them.
  • When linked together in polynucleotide chains, the nucleotides always have just one phosphate.
  • Once at least one phosphate is covalently attached, it is known as a nucleotide.

• Phospholipids

  • The third carbon of the glycerol backbone is also occupied by a modified phosphate group.
  • To qualify as a phospholipid, the phosphate group should be modified by an alcohol.
  • The phosphate heads are thus attracted to the water molecules in their environment.
  • The phosphate may be modified by the addition of charged or polar chemical groups.
  • Two chemical groups that may modify the phosphate, choline and serine, are shown here.