Chapter 7.3 Summary

ATP provides energy for cellular work

• ATP: adenosine triphosphate
• adenosine: nitrogen-containing compound adenine + five carbon sugar called ribose
• triphosphate: a "tail" with three phosphate groups
• triphosphate is the source of energy used for most work
• Each phosphate group is negatively charged and repel each other
• ATP tail is like a spring that releases its potential energy when relaxed
• In a chemical reaction one or both phosphate bonds are broken
• Usually only one is resulting in adenosine diphosphate (ADP)
• Three main types of work: chemical work, mechanical work, and transport work
• Chemical work: building large molecules such as proteins
• Mechanical work: contraction of a muscle
• Transport work: pumping solutes across a cellular membrane
• ATP continuously turned into ADP
• ATP can be restored by adding a phosophate group to ADP
• Energy comes from organic molecules in food

Concept Check 7.3

1. In what way is ATP like a compressed spring?

ATP is like a compressed spring because the phosphate groups are negatively charged so the crowding of the negative charges contributes to potential energy stored in the ATP. Storing this energy is like compressing a spring. When the spring relaxes, the potential energy is released.

2. List three main types of cellular work.

The three main types of cellular work are chemical work, mechanical work, and transport work.

3. What is the source of energy for regenerating ATP from ADP?

The source of energy for regenerating ATP from ADP are the organic molecules from food.