Which food component can gut bacteria help break down because human digestive enzymes cannot digest it?

• Dietary fibre from the skin of pears
• Starch from a slice of brown bread
• Protein from a serving of cooked beans

Which statement describes bacteria living in a healthy gut?

• Many cause illness because fibre fermentation damages the gut lining.
• Many help digestion, though some can cause illness.
• Many help digestion by making plant fibre ready for human enzymes to digest.

Gut bacteria ferment every bit of dietary fibre, so none leaves the body in faeces.

In a made-up lab experiment, equal-sized samples contain 90 bacterial cells before a treatment and 10 afterwards. How many fewer cells were counted afterwards?

Layla eats leafy vegetables. Bacteria ferment some of their fibre in her large intestine. How can this help her body?

• It lets gut-lining cells absorb fibre and use it for energy.
• It helps human enzymes digest fibre into small molecules that feed cells in the gut lining.
• It makes small molecules the body can absorb and gut-lining cells can use for energy.

A doctor prescribes an antibiotic for a bacterial throat infection. Why might the patient also develop an upset stomach?

• It can affect helpful gut bacteria and their digestive work.
• It can slow digestion by killing the enzymes that break down food.
• It can block fibre fermentation by making the body absorb fibre before it reaches the gut bacteria.

One child's gut sample has fewer bacterial types than another's. The first child recently took antibiotics. What can the scientist conclude from these two samples alone?

• The samples link the difference to antibiotic use, so the scientist can set diet aside.
• The samples show how well each child digests dietary fibre, so the scientist can compare their digestive health.
• Bacterial types differ, but the cause needs more evidence.

Ben says, "Bacteria digest fibre, so human digestive enzymes are not needed." Which reply best checks his idea?

• Bacteria ferment fibre, which allows human enzymes to stop digesting starch and protein.
• Bacteria ferment some fibre; human enzymes digest food molecules such as starch and protein.
• Bacteria ferment starch and protein; human digestive enzymes digest the plant fibre that bacteria leave behind.