biological molecules - atp

What is ATP?

A nucleotide derivative that transfers energy in cells

What are the components of ATP?

Adenine (nitrogenous base), ribose (pentose sugar), and three phosphate groups

Why is ATP described as a nucleotide derivative?

It has similar structure to nucleotides (base, sugar, phosphate groups) but is modified with extra phosphates

How is ATP synthesised?

By condensation of ADP + Pi, catalysed by ATP synthase

Where does ATP synthesis occur?

In chloroplasts (photosynthesis), mitochondria (aerobic respiration), and cytoplasm (anaerobic respiration)

What type of reaction forms ATP?

Condensation reaction (water removed)

What is the equation for ATP synthesis?

ADP + Pi → ATP + H₂O

How is ATP hydrolysed?

Hydrolysis of ATP into ADP + Pi, catalysed by ATP hydrolase

What type of reaction breaks down ATP?

Hydrolysis reaction (water added)

What is the equation for ATP hydrolysis?

ATP + H₂O → ADP + Pi

What happens when ATP is hydrolysed?

Energy is released for biological processes

What is phosphorylation?

The addition of a phosphate group to another molecule

How does phosphorylation affect molecules?

Makes them more reactive by lowering activation energy

Why is ATP an immediate energy source?

Hydrolysis is a single-step reaction, releasing energy quickly

Why is ATP energy-efficient?

Releases energy in small, manageable amounts, avoiding waste

Why is ATP easily regenerated?

ATP can be resynthesised rapidly from ADP + Pi

Why is ATP a universal energy currency?

It is used by all cells for energy transfer, regardless of organism

What are the advantages of ATP?

Immediate energy source, small manageable amounts, easily regenerated, phosphorylates molecules, universal energy carrier

What are the disadvantages of ATP?

Cannot be stored in large amounts, unstable, cannot move between cells, must be continuously resynthesised

In what processes is ATP used?

Active transport, muscle contraction, biosynthesis (e.g. protein synthesis), DNA replication, cell signalling, phosphorylation

Why is ATP needed for active transport?

Provides energy to change the shape of carrier proteins in membranes

Why is ATP needed for muscle contraction?

Provides energy for actin and myosin cross-bridge movement

Why is ATP needed in biosynthesis?

Supplies energy for condensation reactions such as protein or DNA synthesis

Compare ATP with an RNA nucleotide

ATP has ribose, adenine, and three phosphate groups

Why can ATP not be used for long-term storage?

It is unstable and breaks down quickly, unlike glycogen or lipids

How is ATP linked to mitochondria?

Cells with high energy demand (e.g. muscle, neurons) have many mitochondria to continually resynthesise ATP

Exam-style Q: Why is ATP suited to its role as an energy source?

Provides immediate energy in small amounts, hydrolysis is a one-step reaction, can be regenerated, and phosphorylates other molecules