Concept 8.3: ATP powers cellular work by coupling exergonic reactions to endergonic reactions

Question 1

A cell does three main kinds of work

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Chemical work, Transport work, Mechanical work

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the pushing of endergonic reactions that would not occur spontaneously, such as the synthesis of polymers from monomers

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Chemical work

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the pumping of substances across membranes against the direction of spontaneous movement

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Transport work

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such as the beating of cilia (see Concept 6.6), the contraction of muscle cells, and the movement of chromosomes during cellular reproduction

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Mechanical work

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A key feature in the way cells manage their energy resources to do this work is

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energy coupling, the use of an exergonic process to drive an endergonic one.

Question 6

ATP is responsible for mediating most energy coupling in cells, and in most cases it acts as the immediate source of

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energy that powers cellular work.

Question 7

watch animation energy coupling and learn it

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an adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.

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ATP (adenosine triphosphate)

Question 9

ATP contains the sugar ribose, with the nitrogenous base adenine and a chain of

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three phosphate groups (the triphosphate group) bonded to it

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ATP is also one of the nucleoside triphosphates used to make

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RNA

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the structure of ATP. ATP powers nearly all forms of

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cellular work by providing energy stored in its chemical bonds

Question 12

ATP is composed of three main components

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a 5 carbon ribose sugar molecule, adenine- a nitrogenous base, and a string of phosphate groups

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to construct ATP the sugar ribose attaches to a nitrogenous base adenine which is also bonded to a chain of

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three phosphate groups (the triphosphates group)

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during cellular respiration, glucose release

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energy

Question 15

this energy is stored when a phosphate group is added to __________________ forming ATP or adenosine triphosphate.

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ADP ( adenosine diphosphate)

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ATP releases energy when the covalent bond between phosphate groups break during

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hydrolysis

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this energy is used to

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drive other biochemical reactions

Question 18

watch animation space-filling model of ATP and learn it

Question 19

space-filling model of an ATP molecule shows its three components; in one end, the 3 phosphate groups with their

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purple phosphorus atoms and red oxygen atoms

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on the other end is the nitrogenous base adenine with its

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blue nitrogen atoms, green carbons, and gray hydrogens

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both attached in the middle to a

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ribose sugar with its green carbon atoms, gray hydrogens, and red oxygens

Question 22

watch animation stick model of ATP and learn it

Question 23

The bonds between the phosphate groups of ATP can be broken by

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hydrolysis

Question 24

When the terminal phosphate bond is broken by addition of a water molecule, a molecule of inorganic phosphate, leaves the ATP, which becomes

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adenosine diphosphate, or ADP

Question 25

learn the math of ATP+ H20. I can not make some of the symbols

Question 26

Because their hydrolysis releases energy, the phosphate bonds of ATP are sometimes referred to as

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high-energy phosphate bonds

Question 27

The phosphate bonds of ATP are not unusually strong bonds, as “high-energy” may imply; rather, the reactants (ATP and water) themselves have

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high energy relative to the energy of the products (ADP and ℗ᵢ ).

Question 28

The release of energy during the hydrolysis of ATP comes from the chemical change of the system to a state of lower free energy, not from the.

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phosphate bonds themselves

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the cell’s proteins harness the energy released during ATP hydrolysis in several ways to perform the three types of cellular work—

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chemical, transport, and mechanical.

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with the help of specific enzymes, the cell is able to use the energy released by ATP hydrolysis directly to drive chemical reactions that, by themselves, are

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endergonic

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If the ∆G 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, the coupled reactions are

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exergonic.

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This usually involves phosphorylation, the transfer of a phosphate group from ATP to some other molecule, such as the

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reactant

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The recipient molecule with the phosphate group covalently bonded to it is then called a

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phosphorylated intermediate

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Transport and mechanical work in the cell are also nearly always powered by the

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hydrolysis of ATP

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ATP hydrolysis leads to a change in a protein’s

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shape and often its ability to bind another molecule

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In most instances of mechanical work involving motor proteins “walking” along cytoskeletal elements (Figure 8.11b), a cycle occurs in which ATP is first bound noncovalently to the

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motor protein.

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Next, ATP is hydrolyzed, releasing

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ADP and ℗ᵢ

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At each stage, the motor protein changes its shape and ability to bind the cytoskeleton, resulting in movement of the protein along the

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cytoskeletal track.

Question 39

ATP is a renewable resource that can be regenerated by the addition of

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phosphate to ADP

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The free energy required to phosphorylate ADP comes from exergonic breakdown reactions (catabolism) in the

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cell

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This shuttling of inorganic phosphate and energy is called the

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ATP cycle

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it couples the cell’s energy-yielding (exergonic) processes to the

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energy-consuming (endergonic) ones.

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As organisms live and grow, they are constantly in the process of making and breaking bonds in

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molecules

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metabolism is the sum of all the

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chemical reactions that take place in an organism

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metabolism includes

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catabolism and anabolism

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catabolism includes the processes that

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break down complex molecules into simpler molecules while harvesting their energy and storing it, usually in the form of ATP

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anabolism includes the process that build more complex

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molecules from simpler molecules

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the energy acquired through catabolic processes is used to

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drive anabolic processes

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neither catabolism nor anabolism is completely efficient, so, at each step some of the available energy is lost into the

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environment as heat

Question 50

Because both directions of a reversible process cannot be downhill, the regeneration of ATP is necessarily

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endergonic