Chemical Energy and Biological Processes

This page delves into the role of chemical energy in biological systems and introduces ATP as a key energy carrier.

The text explains that chemical energy drives changes in biological systems by making and breaking chemical bonds. It distinguishes between heterotrophic organisms, which derive energy from food, and autotrophic organisms, which convert light energy to chemical energy through photosynthesis.

The page then focuses on ATP (adenosine triphosphate) as the primary energy carrier in organisms. Key points include:

• ATP is not an energy store but makes energy available when needed
• The human body contains only about 5g of ATP but makes and breaks down about 50kg daily
• ATP is synthesized when energy is available (e.g., in mitochondria) and broken down when energy is needed (e.g., for muscle contraction)

The structure of ATP is also detailed, showing its components:

• Adenine (a purine base)
• Ribose sugar
• Three phosphate groups

Highlight: ATP plays a crucial role in energy transfer within cells, making it a central topic in A Level Biology Eduqas notes.

Example: Green plants are autotrophic organisms that convert light energy to chemical energy through photosynthesis.

ATP and Energy

This page explores the energy dynamics of ATP, focusing on its hydrolysis and synthesis.

The text explains that when energy is needed in living organisms, the enzyme ATPase hydrolyzes ATP. This process breaks the bond between the second and third phosphate groups, converting ATP to ADP (adenosine diphosphate) and releasing an inorganic phosphate ion along with chemical energy.

Key points include:

• The hydrolysis of ATP releases 30.6 kJ per mole
• ATP hydrolysis is an exergonic reaction (releases energy)
• The reverse process, ATP synthesis, is an endergonic reaction (requires energy input)
• Phosphorylation is the addition of a phosphate group to ADP to form ATP

The page also discusses the advantages of using ATP as an energy intermediate compared to using glucose directly:

• ATP hydrolysis is a single, quick reaction
• Only one enzyme is needed for ATP hydrolysis
• ATP releases energy in small, controlled amounts

Definition: Exergonic reaction - a reaction that releases energy (e.g., ATP hydrolysis)

Definition: Endergonic reaction - a reaction that requires an input of energy (e.g., ATP synthesis)

Highlight: Understanding ATP's role in energy transfer is crucial for grasping cellular energetics in Eduqas A Level Biology.