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What three types of work does a cell do?
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What is chemical work? Example?
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| Question | Answer |
|---|---|
| What three types of work does a cell do? | Chemical work, transport work, mechanical work. |
| What is chemical work? Example? | The pushing of endergonic reactions that would not occur spontaneously. Examples: Synthesis of polymers to monomers. (Building monomers to make polymers) |
| What is transport work? Example? | The pumping of substances across membranes against the direction of spontaneous movement. Example: Transport of molecules across membrane |
| What is mechanical work? Example? | The physical movement of organelles. Example: Beating of cilia, contraction of muscle cells, movement of chromosomes during cellular reproduction |
| What is energy coupling? | Use of an exergonic process to drive an endergonic one. Atp is responsible for mediating most energy coupling in cells. |
| What is the role of Atp in energy coupling? | Responsible for mediating most energy coupling in cells. Acts as the immediate source of energy that powers cellular work. |
| What is Atp composed of? | Atp contains sugar ribose, with nitrogenous base Adenine, and chain of three phosphate groups bonded to it. (Atp is one of nucleoside triphosphates used to make RNA) |
| What happens when hydrolysis reacts with phosphate groups? | Molecule of inorganic phosphate leaves Atp, which becomes adenosine diphosphate, or Adp. |
| What is the change of free energy regarding converting Atp to Adp? (measured under standard conditions) | Exergonic reaction, releases 7.3 kcal of energy per mole of Atp hydrolyzed. DeltaG = -7.3 kcal/mol (-30.5 kJ/mol) |
| Equation of conversion of Atp to Adp? | Atp + H2O -> Adp + inorganic phosphate |
| What is the change of free energy regarding converting Atp to Adp under cellular conditions? (which is not standard conditions due to reactant and product concentrations differing from 1 M) | DeltaG is about -13 kcal/mol, 78% greater than energy released by Atp hydrolysis under standard conditions |
| Why is Atp so useful to the cell? | Energy it releases is somewhat greater than the energy most other molecules could deliver. |
| In regards to heat, what happens when Atp is hydrolyzed? It is beneficial in SOME cases in cell. How is beneficial? | Heat is released to surroundings. Beneficial because when shivering, Atp is hydrolyzed during muscle contraction to generate heat and warm body. |
| *Note* Overall, in most cases of cell, generation of heat alone would be inefficient and likely dangerous use of valuable energy resource. | :) |
| How does cell control heat generation of Atp? | Cell's proteins harness energy released during Atp hydrolysis directly to drive chemical reactions that, by themselves, are endergonic. |
| *Note* If DeltaG of an endergonic reaction is less than the amount of energy released by Atp hydrolysis, then the two reactions can be coupled so that overall, coupled reactions are exergonic. | :) |
| What happens to phosphate group when coupled reactions occur? | Transfer of phosphate group from Atp to some molecule, such as reactant. Recipient with phosphate group covalently bonded to it is called phosphorylated intermediate, more reactive (less stable) than original unphosphor. molecule |
| *Note* Transport and mechanical work in cell are also nearly always powered by hydrolysis of Atp | :) |
| What happens to protein during transport and mechanical work when hydrolysis of Atp occurs? | protein changes shape and changes its ability to bind another molecule. |
| Example of phosphorylation of transport protein? | Atp phosphorylates transport protein that controls flow of solute, causing protein to change shape. Opens downward when phosphor, releases solute by opening upward when unphosphor. (original shape). |
| Example of phosphorylation with mechanical work? | Motor proteins "walking" along cytoskeleton elements. Atp is first noncovalently to the motor protein. Atp is then hydrolyzed, releasing Adp and inorg. phosphate. Another Atp molecule can then bind. Motor prot. changes its shape + ability to bind |
| How can Atp be regenerated? | It is renewable resource, regenerated by addition of phosphate of Adp |
| Where does free energy required to phosphorylate Adp come from? | Comes from the exergonic breakdown reactions (catabolism) in cell |
| *Note* Know Atp cycle | :) |
| Atp cycle rate in working muscle cell | Working muscle cell recycles its entire pool of Atp in less than minute. Represents 10 million molecules of Atp consumed and regenerated per second per cell. |
| What provides energy for formation of Atp by adding phosphate group to Adp? | Catabolic, or exergonic reactions |
Created by:
chelseawillia