ATP and Coupled Reactions



ATP and Coupled Reactions

Many reactions in cells are endothermic (require energy), such as protein synthesis.

The energy comes from the breakdown of ATP (adenosine triphosphate); this process provides energy and so is exothermic.

When the energy released by an exothermic reaction drives an endothermic reaction these two reactions are said to be a coupled reaction.

What is ATP (Adenosine triphosphate)?

The ATP Cycle

How do we get energy from ATP?

How much energy do we get from one ATP molecule?

Every time ATP is broken down into ADP, 31 kJ/mol of energy is released.

What is ATP used for?

There are three distinct uses for ATP:

1. Chemical Work - ATP supplies the energy needed to synthesize

macromolecules

2. Mechanical Work - ATP supplies the energy needed to permit

muscles to contract, cilia and flagella to beat,

chromosomes to move and other functions

3. Transport Work - ATP supplies the energy cells need to pump

substances across the cell membrane

An Example of ATP at Work - The Sodium/Potassium Pump

Some substances can move across the cell membrane very easily, such as water. (Usually with the concentration gradient.)

Other substances require energy to move substances against the concentration gradient. This is also accomplished with the help of special proteins.

A common example is the sodium/potassium pump. This pump maintains an imbalance of sodium and potassium in cells. Especially in nerve and muscle cells.

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