Extras B

Question 1

Bacteriophage

Answer 1

A virus that attacks bacteria.
Most bacteriophages consist of a protein head
surrounding a molecule of DNA. Protein tail and
tail fibres attach the bacteriophage to a bacterial
cell and inject the DNA into it. New
bacteriophages then develop inside the
bacterium. They are released and infect other
cells.

Question 2

Barr body, Barr bodies

Answer 2

Each body cell in a
female mammal contains two X chromosomes.
Only one of these functions; the other is
inactive. The inactive chromosome is coiled up
tightly and forms a structure called a Barr body.
If you look through a microscope at
appropriately stained cheek cells from a human
female you can see the Barr body as a small,
densely stained spot just inside the nuclear
envelope.

Question 3

Bile salts

Answer 3

One of the components of bile, which is
formed in the liver. Bile is secreted into the
small intestine. Here, the bile salts make the
digestion of lipids in the diet more efficient by
breaking them down into tiny droplets. This
increases the surface area on which lipiddigesting
enzymes act.

Question 4

Biodegradable

Answer 4

The molecules of substances
which are biodegradable can be broken down
into smaller molecules and ions by
microorganisms such as bacteria and fungi.
Most paper and wood products are
biodegradable but many plastics are not.

Question 5

Biofuels, Biofuel Fuels

Answer 5

that are produced directly
from living material or from the action of living
organisms. Vegetable oil from sunflower seeds,
ethanol formed by the fermentation of sugar
cane waste, and methane produced from sewage
are all examples of biofuels. Biofuels provide a
renewable energy source and do not have a longterm
effect on atmospheric carbon dioxide
concentration.

Question 6

Biological control

Answer 6

The use of the natural
parasites or predators of a pest to limit its
numbers and reduce the amount of harm it does.
An example of biological control is spraying
maize plants with the bacterium Bacillus
thuringiensis to kill caterpillars of the corn borer
moth.

Question 7

Bronchiole

Answer 7

One of the small airways in the lung

that goes from the larger bronchi to the alveoli.

Question 8

Bronchus, Bronchi

Answer 8

One of the large airways that
take air into and out of the lungs. When a person
breathes in, air enters through the nose and
mouth and is then drawn down the trachea. The
trachea splits into two main bronchi, one going
to the right lung and one to the left. The main
bronchi divide into smaller ones, and then into
bronchioles.