Food from outside

The idea

Maintenance needs energy from outside the body; transferring this energy source, food, from outside to inside is nutrition, which also supplies raw material for growth; most food sources are carbon-based.

Sitting still in class

You sit still in class for a whole hour. You do not run, jump or lift anything.

Does your body use energy in that hour?

• Yes. Keeping its order costs energy even at rest
• No. Energy is only used when we move
• Only the brain does

Keep the tank filled

This body sits still. Every hour its energy tank drops by one. Tap a food to move it from outside to inside. Keep the body going for six hours.

Energy from outside

Maintenance needs energy from outside the body. The process of taking this energy source, food, from outside to inside is nutrition. It also gives the raw material for growth. Most food sources are carbon-based.

Carbon-based means the molecules have carbon atoms in them, like the sugars and starch in roti.

• What we saw | What it shows
• The tank dropped even at rest | Maintenance needs energy all the time
• Food moved from the shelf into the body | Nutrition: food goes from outside to inside
• Roti, banana, dal and milk had carbon chains | Most food sources are carbon-based
• Sand did not work | Not every thing outside is a food

Notes

Maintenance needs energy from outside the body; transferring this energy source, food, from outside to inside is nutrition, which also supplies raw material for growth; most food sources are carbon-based.

Check yourself

A patient lies in bed all week and does nothing. A doctor still says he needs food. Why?

What do we call the process of taking food from outside the body to the inside?

A young child eats food to grow taller. Besides energy, what does the food give her?

Rice, bread and bananas have something in common as food sources. What?

• Food is needed only for moving about. A still body still repairs itself. That needs energy.
• The body stores enough energy to run for ever. The tank ran down every hour. Energy has to be supplied from outside.
• Even a resting body spends energy on upkeep, and food brings that energy in — correct. Yes! Maintenance goes on even at rest, and its energy comes from outside.
• Nutrition — correct. Yes! Nutrition moves the energy source, food, from outside to inside.
• Respiration. Respiration uses oxygen to break food down. It does not bring food in.
• Excretion. Excretion removes wastes from the body.
• Nothing. Growth needs no food. Growth needs additional raw material from outside.
• Raw material for growth — correct. Yes! A growing body needs extra material from outside.
• Oxygen. Oxygen comes from the air, not from food.
• They are made of metals. Food is not made of metals. Its molecules are built on carbon atoms.
• They contain no energy. They carry the energy our body needs.
• They are mostly carbon-based — correct. Yes! Life on earth depends on carbon-based molecules, so most food sources are carbon-based.