Oxygen meets food

The idea

Respiration is the process of acquiring oxygen from outside the body and using it to break down food sources, through oxidising-reducing reactions, for cellular needs.

Why keep breathing?

You breathe in all day and all night, without ever thinking about it.

What does your body do with the oxygen it takes in?

• Its cells use it to break food down and release energy
• Oxygen itself is the energy we use
• Oxygen is stored as food

Breathe in, break down

The food is waiting inside a cell. The oxygen is outside the body. Do the two steps in order.

Oxygen in, food broken

Respiration is the process of acquiring oxygen from outside the body and using it to break down food sources, through oxidising-reducing reactions, for cellular needs.

Oxygen is not the energy. The energy comes out of the food that is broken down.

• Part of respiration | What happens
• Acquire | Oxygen is taken in from outside the body
• Use | The oxygen breaks the food down in the cells
• Result | Energy for the cell's needs

Notes

Respiration is the process of acquiring oxygen from outside the body and using it to break down food sources, through oxidising-reducing reactions, for cellular needs.

Check yourself

In respiration, where does the energy come from?

Which statement about respiration is correct?

When oxygen breaks food down, the food gains oxygen. In Chapter 1, gaining oxygen was called …

Which part of respiration does breathing do?

• From the oxygen itself. Oxygen is not energy. It breaks the food down, and the energy comes from the food.
• From the food that is broken down — correct. Yes! The energy is locked in the food. Oxygen helps to break it down.
• From the air we breathe out. The air we breathe out carries wastes away. It is not an energy source.
• It means breathing air in and out, and nothing more. Breathing brings the oxygen in, but respiration also uses it to break food down.
• It is how plants make food from sunlight. That is photosynthesis. Respiration breaks food down.
• It takes oxygen from outside and uses it to break food down for the cell's needs — correct. Yes! Both parts together make respiration.
• oxidation, so the food is oxidised — correct. Yes! Respiration is an oxidising-reducing reaction.
• reduction, so the food is reduced. Reduction is the loss of oxygen. Here the food gains oxygen.
• rancidity, so the food turns rancid. Rancidity is oils and fats going bad. Gaining oxygen in a reaction is called oxidation.
• Breaking food down in the cells. That part happens in the cells, using the oxygen that breathing brought in.
• Acquiring oxygen from outside the body — correct. Yes! Breathing brings the oxygen in.
• Making food from sunlight. That is photosynthesis in green plants.