Extras D

Question 1

Deamination

Answer 1

If more protein is eaten than is
required, the excess amino acids which result
cannot be stored. They are broken down in the
liver where the amino group is removed and, in
mammals, converted to urea, the main nitrogencontaining
waste substance produced in a
mammal. The first part of this reaction is
deamination.

Question 2

Dermis

Answer 2

The layer of living cells that lies under
the dead cells of the epidermis in the skin. It
consists of connective tissue in which are blood
vessels, sensory nerve endings, sweat glands and
hair follicles.

Question 3

Dehydrogenation

Answer 3

A chemical reaction in which a
molecule loses hydrogen. When a molecule
loses hydrogen it is also oxidised; the molecule
that gains the hydrogen is reduced.

Question 4

Diaphragm

Answer 4

A thin sheet of muscle situated
between the lungs and the abdominal organs of a mammal. Contraction of this muscle causes the
diaphragm to flatten and air to be drawn into the
lungs.

Question 5

Digestion, Digest

Answer 5

The process in which the large
insoluble molecules which make up an
organism’s food are broken down by enzymes to smaller soluble molecules. Mammals such as
humans have specialised guts. Saprobionts such
as bacteria and fungi secrete enzymes over the
surface of their food. They then absorb the
soluble molecules of digested food through their
outer surface.

Question 6

Dihybrid inheritance

Answer 6

A genetic cross involving
genes at two different loci. The inheritance of
one pair of alleles does not affect the inheritance
of the other pair because chromosomes act
independently of one another during gamete
formation.

Question 7

Disinfectant

Answer 7

A substance that kills
microorganisms when they are outside the
body. Because they kill bacteria they may be
described as bactericidal. Some disinfectants,
when used at low concentrations, can be used on
the human body as antiseptics.

Question 8

Dispersal, Disperse

Answer 8

The way offspring of an
organism are spread and reach new areas. The
seeds and fruits of flowering plants, for
example, have different adaptations which result
in the plant being able to disperse and colonise
new areas. This helps to reduce competition
between the parent plant and its offspring.

Question 9

Dorsal

Answer 9

The back or upper surface of an animal or
a structure associated with it. The dorsal fin of a
shark, for example, is the fin on its back, which
is visible when the shark is swimming at the
surface.

Question 10

Dormant, Dormancy

Answer 10

A dormant seed is one that
does not germinate and grow immediately, even
if the environmental conditions are favourable.