Biology Chapter on ATP

Questions and Answers

What is the primary reason adenosine triphosphate (ATP) is considered the universal energy currency of cells?

It is only used in photosynthetic organisms.

It is easily hydrolysed to release energy. (correct)

It can be stored in large quantities within cells.

It remains unchanged during metabolic reactions.

Which feature of ATP allows it to be efficiently recycled from ADP?

It can only be formed in the mitochondria.

It is easily phosphorylated. (correct)

It is a highly stable molecule.

It is a large molecule with multiple branches.

How much energy is released when the terminal phosphate group is removed from ATP?

30.5 kJ mol^-1

45.0 kJ mol^-1

14.2 kJ mol^-1 (correct)

20.0 kJ mol^-1

What role does ATP synthase play in cellular metabolism?

It catalyzes the phosphorylation of ADP to form ATP. Signup and view all the answers

Which of the following processes does NOT involve the synthesis of ATP?

Hydrolysis of ATP Signup and view all the answers

What is a significant characteristic of the covalent bonds linking the phosphate groups in ATP?

They are unstable and have low activation energy. Signup and view all the answers

Approximately how much ATP does a single human use in a 24-hour period?

65 kg Signup and view all the answers

What type of reaction is the conversion of ADP back to ATP?

Phosphorylation Signup and view all the answers

Study Notes

Adenosine Triphosphate (ATP)

ATP is the universal energy currency for all cells, playing a crucial role in energy-requiring processes.
It is a small, water-soluble molecule, allowing easy transport within the cell.

Properties of ATP

Immediate energy source: ATP can release energy in a one-step reaction.
Easily hydrolyzed: Hydrolysis of ATP releases energy due to unstable bonds between phosphate groups.
Recyclable: ATP is continually recycled from ADP (adenosine diphosphate) through phosphorylation.
Efficient and sufficient: The energy quantity released satisfies cellular needs, with minimal waste.

Energy Release and Phosphate Bonds

ATP contains three negatively charged phosphate groups that repel each other, creating unstable covalent bonds.
Each bond breaks easily, releasing significant energy:
- 30.5 kJ mol⁻¹ for the first two phosphates,
- 14.2 kJ mol⁻¹ for the final phosphate.

ATP-ADP Cycle

The conversion of ATP to ADP is reversible; an inorganic phosphate can be added back to reform ATP.
Despite only around 50 g of ATP present in a human body at any time, approximately 65 kg of ATP are utilized over 24 hours.
Each ATP molecule can undergo roughly 1300 cycles of synthesis and hydrolysis daily.

Phosphorylation and ATP Synthesis

ATP synthesis from ADP involves phosphorylation, facilitated by ATP synthase.
Three methods of phosphorylation:
- Photophosphorylation: Occurs in the grana of chloroplasts during photosynthesis.
- Oxidative phosphorylation: Takes place on the inner mitochondrial membrane in both plant and animal cells during electron transport.
- Substrate-level phosphorylation: Transfers phosphate from donor molecules to ADP in cellular processes, such as glycolysis bordering on pyruvate formation.

Description

This quiz explores the significance of adenosine triphosphate (ATP) as the universal energy currency in cells. It covers its properties, how it provides immediate energy, and its recycling process. Test your understanding of how ATP functions in cellular processes.