Extras H

Question 1

Haemoglobin

Answer 1

A protein found in the blood of
many animals. Its main function is the transport
of oxygen.

Question 2

Hermaphrodite

Answer 2

An organism which produces
both male and female sex cells or gametes.
Many flowering plants have both male and
female sex organs and are hermaphrodites. The
condition is not so common in animals but a
familiar example of a hermaphrodite animal is
the earthworm.

Question 3

Helicobacter

Answer 3

Spiral-shaped bacteria found in the
stomach lining of many middle-aged people.
The presence of Helicobacter can cause stomach
ulcers.

Question 4

Herbicide

Answer 4

A chemical that is used to kill plants.
Glyphosate is an example of a broad-spectrum
herbicide. This means that it kills not only weeds
but also crop plants.

Question 5

Homeobox gene

Answer 5

A gene that determines how an
animal develops. Homeobox genes code for
proteins that bind to DNA and activate
particular genes.

Question 6

Hybrid, Hybridise, Hybridising

Answer 6

The offspring
of a cross between two different varieties or
between two closely related species. Triticale is
a cereal which is particularly important in
Eastern Europe. It was produced by hybridising
wheat and rye.

Question 7

Hybrid vigour

Answer 7

Hybrids may be produced by
crossing plants which have been inbred for
many generations. These inbred lines are usually
not very productive because they are
homozygous for a number of unfavourable
recessive alleles. When plants from these inbred
lines are crossed, the F1 hybrids produced will
be heterozygous for most of these alleles. These
F1 plants will produce much higher yields than
either of the parent strains. This higher yield is
described as hybrid vigour.

Question 8

Hydrocarbon

Answer 8

A substance whose molecules
contain only the elements hydrogen and carbon.
Methane (CH4) is a hydrocarbon. It is an
important greenhouse gas. Biologically
important fatty acids have a COOH group at
one end of the molecule and a long hydrocarbon
tail at the other.

Question 9

Hyphae

Answer 9

Fungi are made up of a mass of
branched thread-like structures called hyphae. In
the soil, fungi play a very important part in
digesting dead plant material. The hyphae
secrete enzymes which digest large molecules,
such as cellulose and lignin. They break them
down into small soluble molecules, which are
then absorbed over the large surface produced
by the branching hyphae.

Question 10

Hypercholesterolaemia

Answer 10

A condition in which
there is a high concentration of cholesterol in
the blood. Familial hypercholesterolaemia is an
inherited condition in which cells do not have
the receptors necessary to absorb cholesterol
from the blood.