Health and disease, Year 8: more practice

Oranges

HintLook for the food rich in vitamin C.

The whyCitrus fruits are rich in vitamin C. Without it the body cannot make and repair the tissue that holds the gums and skin together.

The skin makes vitamin D when it is exposed to sunlight

HintYour body can manufacture this nutrient itself, not just eat it.

The whyVitamin D helps the body absorb calcium for bones. Without it the bones can stay soft and bend.

Iron is needed for haemoglobin, so the blood carries less oxygen

HintThink about what red cells carry around the body.

The whyHaemoglobin in red blood cells carries oxygen. Without enough iron the body cannot make it, so less oxygen reaches the cells.

A disease caused by a lack of a nutrient in the diet

HintIt is about something missing.

The whyScurvy, rickets and anaemia are examples. They are cured by eating enough of the missing nutrient.

Carbon monoxide

HintIt also comes out of car exhausts.

The whyCarbon monoxide joins on to haemoglobin instead of oxygen. The heart must work harder to supply the body.

It slows down the nervous system and brain activity

HintThink of the opposite of speeding up.

The whyMessages travel more slowly, so judgement, balance and reactions are affected.

The single cell carries out all the life processes itself

HintThink about how many cells it has.

The whyA bacterium or amoeba feeds, respires, excretes, grows and reproduces inside one cell.

By splitting in two (binary fission)

HintThe cell makes a copy of itself.

The whyA bacterium copies its genetic material and divides in two. In good conditions this can happen every 20 minutes or so.

Carbon dioxide

HintIt forms bubbles in the dough.

The whyYeast respires the sugars in dough and releases carbon dioxide. The gas bubbles stretch the dough and it rises.

The athlete uses more energy

HintThink about how much each person burns.

The whyEnergy needs depend on how active you are. Taking in more than you use is stored as fat, and less than you use makes you lose mass.