Extras C

Question 1

Callus

Answer 1

In the micropropagation of plants, a
single cell develops into a mass of cells called a
callus. The callus cells are treated with plant
growth substances; stems, leaves and roots then
form. In this way new plants are produced.

Question 2

Campylobacter

Answer 2

Spiral-shaped bacteria that are
one of the commonest causes of food poisoning.
Symptoms of Campylobacter food poisoning
generally last from three to five days and include
headache, vomiting and diarrhoea.

Question 3

Cancer

Answer 3

A tumour or swelling resulting from the
uncontrolled division of cells. These abnormal
cells rapidly increase in number, invading and
destroying the surrounding tissues. Individual
tumour cells eventually break away from the
original tumour. They are carried by the blood or
the lymphatic system to other areas of the body
where they form new tumours.

Question 4

Carbon sink

Answer 4

A stage in the carbon cycle in
which carbon remains locked. Coal was formed
from plants that grew in swampy conditions.
When these plants died, they did not decay and
the carbon they contained was not released as
carbon dioxide. It remained locked up in the
coal.

Question 5

Carcinogen

Answer 5

A substance which will cause
cancer. Many organic substances, such as those
found in the tar in cigarette smoke, are
carcinogens. They damage DNA. Cells in which
the DNA is damaged may become cancerous.
This is more likely when there is an inherited
tendency to develop cancer.

Question 6

Cardiopulmonary

Answer 6

A word meaning ‘to do with

the heart and lungs’.

Question 7

Cataract

Answer 7

The clouding of the lens of the eye
resulting in blurred vision. The commonest type of cataract is associated with old age but
cataracts also occur in younger people. They
may be treated surgically and vision restored
with the aid of glasses, contact lenses or an
artificial lens inserted into the eye.

Question 8

Catheter

Answer 8

A flexible tube which may be inserted
into a narrow opening. Catheters are used in
balloon angioplasty, a form of treatment that
may be used in patients with severe coronary
heart disease. A catheter is inserted into an
artery in the groin and threaded into a blocked
coronary artery. A tiny balloon at the tip of the
catheter is then inflated, to help improve blood
flow.

Question 9

CD4 receptor

Answer 9

A receptor molecule found in the
cell surface membrane of a particular type of
lymphocyte called a T cell. These receptors are
involved in the immune response. A T helper
cell with a complementary-shaped CD4 receptor
on its surface, binds to the antigen fragment
displayed by the antigen-presenting cell.

Question 10

Cellulase

Answer 10

An enzyme that digests cellulose into
soluble sugar; this reaction involves the addition
of water molecules so it is an example of
hydrolysis. Cellulase is produced by many
different microorganisms but it is not produced
by animals. An animal such as a cow can digest
cellulose because it has large numbers of
bacteria and other microorganisms in its gut. It
is these microorganisms that produce the
necessary cellulase enzymes.

Question 11

Chemosynthetic autotroph

Answer 11

Chemosynthetic
autotrophs or chemoautotrophs are organisms
which use the energy from another chemical
reaction to build up the organic molecules they
require from small inorganic molecules, such as
carbon dioxide and water. For example,
chemosynthetic bacteria are chemoautrophs.

Question 12

Chitin

Answer 12

A nitrogen-containing polysaccharide.
Chitin is found in the tough outer skeleton of
insects and in the cell walls of fungi.

Question 13

Chlorophyll

Answer 13

The green pigment found in plants
and other organisms that photosynthesise. It is
responsible for the capture of energy from
sunlight.

Question 14

Chorionic, Chorion

Answer 14

The chorion is one of the
membranes that surround a developing fetus in
the uterus of its mother. The chorion helps to
form the placenta. It is folded and forms small
finger-like projections. Each of these projections
is called a chorionic villus.

Question 15

Chromosome, Chromosomes

Answer 15

One of the threadlike
structures in the nucleus into which DNA is
organised. Only during cell division, when
chromosomes become shorter and thicker, can
they clearly be identified as distinct structures. A
chromosome consists of DNA, a small amount
of RNA, and various proteins, some of which
are involved in packaging the DNA. In bacteria,
the DNA forms a loop which is sometimes
called a bacterial chromosome. It is not a true
chromosome because it does not contain
packaging proteins.

Question 16

Chromosome puff

Answer 16

Some insect cells have very
large chromosomes called giant chromosomes.
These giant chromosomes are visible at all
stages of the cell cycle. When a gene on these
giant chromosomes is active, the part of the
chromosome on which this gene is situated
unravels and spreads out to form a chromosome
puff.

Question 17

Classical conditioning

Answer 17

In this form of learning
an unrelated stimulus, referred to as a neutral
stimulus, produces the same response as was
produced by the original unconditioned
stimulus. The Russian scientist, Pavlov, taught
dogs to salivate at the sound of a bell. The
neutral stimulus, the sound of a bell, became
associated with the original unconditioned
stimulus, receiving food, and eventually caused
the dog to salivate even when no food was
present. This is the conditioned response.

Question 18

Cleavage

Answer 18

The process of mitosis results in the
formation of two nuclei which are genetically
identical. After mitosis has taken place, the
cytoplasm divides and two new cells are
formed. We call the division of the cytoplasm
cell cleavage.

Question 19

Climate

Answer 19

All the weather-related conditions such
as rainfall, wind exposure, and extremes of
temperature make up the climate that affects an
ecosystem.

Question 20

Cnidaria

Answer 20

The group of animals that contains
jellyfish, sea anemones and corals. Many
cnidaria have specialised stinging cells with
which they catch their prey.

Question 21

Codominant, Codominance

Answer 21

A pair of alleles are
said to be codominant if both are expressed in
the phenotype of the heterozygote. In plants
such as antirrhinums, flower colour is
determined by a single gene with two alleles,
CR and CW. The homozygote CRCR has red
flowers. CWCW has white flowers. The
heterozygote CRCW has pink flowers. As both
alleles are expressed in the pink flowers, these
alleles are referred to as being codominant.

Question 22

Collenchyma

Answer 22

A type of supporting tissue found
in plants. Collenchyma cells are slightly
elongated and have their cell walls strengthened
with extra cellulose at the corners.

Question 23

Columnar epithelium

Answer 23

Epithelial cells are cells
that form the outer surface of many animals.
They also line cavities inside organs. Epithelial
cells differ in shape. Columnar epithelial cells are, as their name suggests, tall and thin, and line
the small intestine and the airways of the lungs

Question 24

Congenital disease

Answer 24

A disease or condition that is
present at birth. Congenital conditions may be
inherited, like sickle cell anaemia or cystic
fibrosis. They may also result from an
environmental factor such as the effect of drugs
or the consumption of too much alcohol by the
mother during pregnancy, or the acquisition of a
disease such as HIV.

Question 25

Connective tissue

Answer 25

Tissue that is found in animals
and supports or binds together other tissues in
the body. Connective tissue forms tendons,
ligaments and bones. Blood is a specialised
connective tissue.

Question 26

Consumer

Answer 26

Consumers are heterotrophs as they
obtain their organic matter by feeding on other
organisms. In the food chain: nettle plant 
nettle aphid  two-spot ladybird, the aphid and
ladybird are both consumers. Primary
consumers eat plant material. Secondary
consumers feed on primary consumers.

Question 27

Counselling

Answer 27

Technique to help someone make a
decision for themselves by talking the
possibilities through with someone else.

Question 28

Cyclin

Answer 28

A protein that helps to regulate and
control the events of the cell cycle. The levels of
different cyclins in the cell rise and fall. It is
these changes in concentration that control the
cell’s progression from one stage in the cell
cycle to the next.

Question 29

Cyclin-dependent kinase, CDK

Answer 29

An enzyme that
plays an important part in regulating and
controlling the events of the cell cycle. The
enzyme combines with proteins called cyclins.
This leads to the activation of other proteins
involved with such processes as the breakdown
of the nuclear envelope and the formation of the
spindle.

Question 30

Cytoplasm

Answer 30

The cytoplasm is a jelly-like fluid
surrounded by the cell surface membrane. Ions,
sugars and amino acids are dissolved in
cytoplasm, and large molecules are suspended. It
also contains a network of proteins, which help to give the cell its shape. Organelles such as
mitochondria are suspended in the cytoplasm.