Before storage molecules can be used for energy, they must be broken down so that their chemical bonds can be accessed and their energy transferred into usable ATP for the cell.

Quick Scoop

Think of storage molecules (like fats, starch, or glycogen) as tightly packed “energy boxes.” To turn those boxes into usable power, cells have to unpack them first.

1. They must be broken down (catabolism)

Storage molecules are usually big molecules (polysaccharides, fats, sometimes proteins), made of many smaller subunits linked together.

  • Carbohydrate stores (starch in plants, glycogen in animals) are broken into simple sugars such as glucose.
  • Fat stores (triglycerides) are broken into glycerol and fatty acids.
  • In extreme cases, proteins can be broken into amino acids for energy.

This breakdown is done by enzymes, step by step, so energy is released in small, controllable amounts instead of all at once.

2. Their bonds must be oxidized (energy release)

The real energy is in the covalent bonds, especially all those C–H bonds in sugars and fats.

  • As the molecules are broken down, they are oxidized (they lose electrons and hydrogen atoms).
  • This controlled oxidation happens through pathways like glycolysis and further steps in cellular respiration for glucose.

This doesn’t “burn” them like fire, but uses many tiny chemical steps to release the energy safely.

3. Energy must be captured in ATP (usable form)

Cells can’t directly use the raw bond energy; they need it packed into a handy “battery” molecule, ATP.

  • Enzymes couple the breakdown steps to the production of ATP and high‑energy carriers such as NADH.
  • The end result is that the energy from storage molecules ends up trapped in ATP’s high‑energy phosphate bonds.

Once ATP is made, the cell can spend it on muscle contraction, active transport, building new molecules, and more.

4. A simple story version

Imagine a cell as a city with warehouses full of energy bars.

  1. The warehouse shelves (storage molecules) are full of big boxes (polysaccharides or fats).
  1. Workers (enzymes) open the boxes and unwrap the bars into smaller pieces (glucose, fatty acids).
  1. Machines in a power plant (cellular respiration pathways) “digest” those pieces and convert the released energy into batteries (ATP).
  1. The city uses those batteries to power lights, factories, and transport (all cell processes).

So, in one line:

Storage molecules must be enzymatically broken down and oxidized so that their bond energy can be captured in ATP, which the cell can then use for work.

TL;DR:
What needs to happen to storage molecules before they can be used for energy?
They must be broken down into smaller molecules and oxidized so the energy in their bonds can be transferred into ATP, the cell’s usable energy currency.

Information gathered from public forums or data available on the internet and portrayed here.