Phosphate compounds and thermodynamics

Question 1

Examples of high energy compounds

Answer 1

-phosphate anhydride
- phosphate esters (ATP)
- Acetyl-CoA’s carbon-sulfur bond

Question 2

How do high energy compounds provide energy?

Answer 2

• by coupling with unfavorable reactions.

Question 3

What does it mean for a molecule to be high energy?

Answer 3

• high ΔG (change in free energy) between the solvated hydrolysis products (ADP + Pi) and solvated reactants (ATP)

Question 4

Approximate Δ G°’ (ATP hydrolysis) value

Answer 4

• -30 kJ/mol

Question 5

Approximate cellular conditions

Answer 5

• -50 kJ/mol

Question 6

Need about 65 kg/day, but only 50g of ATP is present, so what do we have?

Answer 6

• a great recycling system that can reuse ATP (ETC)

Question 7

What are the reasons that ATP is a high energy compound?

Answer 7

• resonance competition
• removal of electrostatic repulsion
• Greater ΔG released when ADP + Pi are solvated vs ATP solvated
  LOOK UP WHY

Question 8

What is resonance competition?

Answer 8

• after hydrolysis theres a greater number of more stable resonance contributors

Question 9

Why is ATP a good choice?

Answer 9

• partial resonance character means there are stronger (double bonds) and substantial ΔG activation
• still hydrolysable and entropic gain upon hydrolysis