Energy and ATP
Energy and ATP
- Cells need a steady supply of energy, which they get from respiration.
- Energy powers active transport, movement, and anabolic reactions (building big molecules).
- The molecule that delivers it is ATP.
Practice
Which is a use of energy in a cell?
Energy from respiration drives active transport, movement (e.g. muscle), and anabolic (building) reactions.
The energy currency
- ATP is made from ADP + a phosphate; breaking that phosphate off again releases a small, usable burst of energy.
- It is the universal energy currency because it:
- releases energy quickly, in small amounts that match a cell's needs,
- is easily re-made over and over,
- is small and soluble, so it moves easily around the cell.
Practice
Why is ATP a good energy currency?
ATP gives small, quick bursts of energy, is re-made repeatedly, and is small and soluble so it moves easily.
Practice
ATP is made from:
Adding a phosphate to ADP makes ATP; removing it again releases energy.
How ATP is made
- by phosphorylation — direct transfer of a phosphate group.
- by chemiosmosis — across the membranes of mitochondria and chloroplasts.
Practice
Chemiosmosis makes ATP using:
Chemiosmosis uses a proton gradient across the inner membrane to drive ATP synthase.
You've got it
Key idea
- energy (from respiration) powers active transport, movement, anabolic reactions
- ATP = ADP + phosphate; the universal energy currency (quick, small bursts; re-made; small + soluble)
- ATP is made by phosphorylation and chemiosmosis (across mitochondrial/chloroplast membranes)