what is it about the structure of atp that allows it to power biological reactions?
ATP AND BIOLOGICAL Energy
Tabular array of Contents
The Nature of ATP | How to Make ATP | Learning Objectives | Terms | Links
The Nature of ATP | Back to Top
Adenosine triphosphate (ATP) , the energy currency or money of the cell pictured in Figfures 1 and 2, transfers free energy from chemical bonds to endergonic (energy absorbing) reactions within the cell. Structurally, ATP consists of the adenine nucleotide ( ribose carbohydrate, adenine base, and phosphate grouping, PO4 -2) plus two other phosphate groups.
Figure 2. A cartoon and space-filling view of ATP. Image from Purves et al., Life: The Science of Biology, quaternary Edition, by Sinauer Assembly ( world wide web.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.
Energy is stored in the covalent bonds between phosphates, with the greatest amount of free energy (approximately 7 kcal/mole) in the bail betwixt the second and third phosphate groups. This covalent bond is known every bit a pyrophosphate bail.
We tin can write the chemical reaction for the germination of ATP as:
a) in chemicalese: ADP + Pi + energy ----> ATP
b) in English language: Adenosine diphosphate + inorganic Phosphate + energy produces Adenosine Triphosphate
The chemical formula for the expenditure/release of ATP energy can be written every bit:
a) in chemicalese: ATP ----> ADP + energy + Pi
b) in English Adenosine Triphosphate produces Adenosine diphosphate + free energy + inorganic Phosphate
An analogy between ATP and rechargeable batteries is appropriate. The batteries are used, giving upward their potential energy until it has all been converted into kinetic free energy and oestrus/unusable energy. Recharged batteries (into which energy has been put) can exist used but after the input of additional energy. Thus, ATP is the higher energy form (the recharged battery) while ADP is the lower energy class (the used bombardment). When the terminal (third) phosphate is cut loose, ATP becomes ADP ( Adenosine diphosphate ; di= two), and the stored free energy is released for some biological process to utilize. The input of additional energy (plus a phosphate group) "recharges" ADP into ATP (as in my analogy the spent batteries are recharged by the input of additional free energy).
How to Make ATP | Back to Tiptop
Ii processes convert ADP into ATP: one) substrate-level phosphorylation; and 2) chemiosmosis . Substrate-level phosphorylation occurs in the cytoplasm when an enzyme attaches a third phosphate to the ADP (both ADP and the phosphates are the substrates on which the enzyme acts). This is illustrated in Figure 3.
Figure 3. Enzymes and the formation of NADH and ATP. Images from Purves et al., Life: The Science of Biology, 4th Edition, past Sinauer Associates ( www.sinauer.com ) and WH Freeman ( world wide web.whfreeman.com ), used with permission.
Chemiosmosis, shown in Figure 4, involves more than than the unmarried enzyme of substrate-level phosphorylation. Enzymes in chemiosmotic synthesis are arranged in an electron transport chain that is embedded in a membrane. In eukaryotes this membrane is in either the chloroplast or mitochondrion . According to the chemiosmosis hypothesis proposed past Peter Mitchell in 1961, a special ATP-synthesizing enzyme is besides located in the membranes. Mitchell would afterwards win the Nobel Prize for his work.
Effigy 4. A typical representation of an electron transport chain. Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.
During chemiosmosis in eukaryotes, H+ ions are pumped beyond an organelle membrane by membrane "pump proteins" into a confined infinite (bounded by membranes) that contains numerous hydrogen ions. This is shown in Figure 4 and 5. The energy for the pumping comes from the coupled oxidation - reduction reactions in the electron transport concatenation . Electrons are passed from i membrane-leap enzyme to another, losing some energy with each tansfer (every bit per the 2nd police force of thermodynamics ). This "lost" energy allows for the pumping of hydrogen ions against the concentration gradient (there are fewer hydrogen ions exterior the confined space than there are inside the confined space). The confined hydrogens cannot pass dorsum through the membrane. Their just exit is through the ATP synthesizing enzyme that is located in the circumscribed membrane. Every bit the hydrogen passes through the ATP synthesizing enzyme, free energy from the enzyme is used to adhere a third phosphate to ADP, converting it to ATP.
Effigy 5. A generalized view of an electron transport system. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Assembly ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.
Usually the concluding phosphate is not but removed, but instead is attached to another molecule. This process is known as phosphorylation .
West + ATP -----> W~P + ADP where Westward is whatever chemical compound, for example:
glucose + ATP -----> glucose~P + ADP
Glucose tin exist converted into Glucose-half-dozen-phosphate past the addition of the phosphate grouping from ATP.
ATP serves as the biological energy company, releasing energy for both anabolic and catabolic processes and being recharged by free energy generated from other catabolic reactions.
Learning Objectives | Back to Meridian
- Describe the components, organization, and functions of an electron ship system .
- ATP is composed of ribose, a five-carbon carbohydrate, 3 phosphate groups, and adenine , a nitrogen-containing compound (also known every bit a nitrogenous base). What class of organic macromolecules is composed of monomers similar to ATP?
- ATP directly or indirectly delivers energy to almost all metabolic pathways. Explain the performance of the ATP/ADP bike.
- Calculation a phosphate to a molecule is chosen phosphorylation . What two methods do cells utilize to phosphorylate ADP into ATP?
Terms | Back to Top
| adenine nucleotide | Adenosine diphosphate | Adenosine triphosphate (ATP) | anabolic | catabolic | chemiosmosis |
| chloroplast | covalent bonds | cytoplasm | electron transport concatenation | endergonic | enzyme |
| mitochondrion | oxidation - reduction | phosphorylation | ribose | second law of thermodynamics |
Links | Back to Top
- Energy View an online slideshow (102 slides) by Susan Blanchard that covers thermodynamics, ATP and all that stuff.
- The Nobel Prize in Chemistry 1997 Three scientists were awarded the Nobel Prize in 1997 for their work studying enzymes involved with the formation and use of ATP. The press release is of particular notation.
- The Nobel Prize in Chemical science 1978 Printing Release Peter D. Mitchell proposed a wild thought well-nigh how ATP was made...and he was subsequently validated by other researchers. Read the Nobel Foundation Press release announcing the prize.
- Small Molecules for Modern Biology This site requires the Chinkle Plugin (available from that site) for your browser. You can view images of a variety of small molecules, including ATP.
- Mitochondrial Mysteries Demystified This site uses the Shockwave Plugin to provide a multimedia tour of the mitochondrion and its role in cellular metabolism.
Text ©1992, 1994, 1997, 1998, 1999, 2000, 2001, 2002, 2007 by M.J. Farabee, all rights reserved.
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