Extra p

Question 1

Pentose

Answer 1

A simple sugar with five carbon atoms in
each of its molecules. Pentoses are
monosaccharides, each molecule consisting of a
single sugar unit. A pentose sugar, ribose, is an
important component of RNA. Deoxyribose is
also a pentose found in DNA

Question 2

Phosphorylation, Phosphorylate

Answer 2

The addition
of a phosphate group to a molecule. Cyclindependent
kinases are enzymes that help to
control the cell cycle. When phosphate is added
to cyclin-dependent kinases, they change shape
and become active. ADP is phosphorylated to
make ATP.

Question 3

Pesticide

Answer 3

A substance used to kill pests.
Pesticides which are targeted at insects are
known as insecticides; those which kill weeds
are herbicides

Question 4

Phosphorylation, Phosphorylate

Answer 4

The addition
of a phosphate group to a molecule. Cyclindependent
kinases are enzymes that help to
control the cell cycle. When phosphate is added
to cyclin-dependent kinases, they change shape
and become active. ADP is phosphorylated to
make ATP.

Question 5

Plasma

Answer 5

The liquid part of the blood. It consists
mainly of water, but about 10% is made up of
dissolved molecules such as glucose, mineral
ions and protein. Plasma leaks out of capillaries
to form tissue fluid which bathes the body cells

Question 6

Plasma proteins

Answer 6

The proteins that are normally
present in the liquid part of the blood, the blood
plasma. These proteins have a number of functions. They play an important part in the
formation of tissue fluid and its return to the
blood; they are involved in the formation of a
blood clot when an injury occurs; they may be
antibodies; and they help to keep the pH of the
blood constant.

Question 7

Pollen tube

Answer 7

When a pollen grain lands on the
stigma of a flower, it starts to grow. It sends out
a long, thin cytoplasm-filled tube called a pollen
tube. This pollen tube grows down through the
style towards the ovary. Eventually the male
gametes will pass down this tube into the
embryo sac and fertilisation will take place

Question 8

Polymers

Answer 8

Large molecules formed from the
linking together of identical or similar subunits
(monomers).

Question 9

Polar nuclei

Answer 9

Two of the nuclei in a plant embryo
sac or ovule. The polar nuclei fuse with one of
the male nuclei in the pollen tube to form a
nucleus with three sets of chromosomes. This
eventually develops into the endosperm, which
provides food for the developing embryo.

Question 10

Pollen

Answer 10

The organ of a seed plant that carries the

male gametes.

Question 11

Posterior

Answer 11

The rear or tail end of an animal

Question 12

Precursor

Answer 12

A molecule from which another
molecule is produced. Alliin is a molecule found
in garlic plants. When the plant is cut or
damaged, an enzyme converts alliin to allicin, a
molecule known to destroy bacteria. In this
reaction, alliin is the precursor.

Question 13

Primate

Answer 13

A member of the group of animals that
includes monkeys and apes. Humans are also
primates. Most primates live in trees, and many
of the characteristics associated with the group,
such as binocular vision and grasping hands, are
adaptations to living in trees.

Question 14

Producer, Primary producer

Answer 14

Producers are
autotrophs and they obtain their organic matter
either by photosynthesis or by using the energy
released from chemical reactions. They are at the
base of all food chains. In the example:
microscopic algae  brine shrimp  flamingo
 eagle, microscopic algae are the producers

Question 15

Progesterone

Answer 15

A female sex hormone produced
during the second half of the reproductive cycle
and during pregnancy. It has a number of effects
on the reproductive system. In particular, it
maintains the lining of the uterus and prevents
the contraction of muscle in the uterus.

Question 16

Protoplast

Answer 16

A plant cell which has had its cell
wall digested away by enzymes. Protoplasts are
often used in genetic engineering. Because they
do not have a cell wall, it is much easier to get a
new gene into a protoplast than into a whole
plant cell.

Question 17

Protozoa

Answer 17

Single-celled eukaryotic organisms,
which belong to the kingdom Protoctista.
Protozoa may be either autotrophic or
heterotrophic. They include free-living forms
such as amoebae and parasites such as the
malarial parasite.

Question 18

Pulmonary

Answer 18

A word meaning ‘to do with the
lungs’. The pulmonary artery, for example,
takes blood to the lungs while the pulmonary
vein returns it from the lungs to the heart.

Question 19

Pupa

Answer 19

The stage between larva and adult in
insects that undergo complete metamorphosis.
At the start of metamorphosis, the larva moults
into a pupa, with a tough, leathery case. Inside
this pupa, many changes occur both externally
and internally as the larva undergoes
metamorphosis. Finally the outer case of the
pupa splits and a new adult emerges.

Question 20

Protease

Answer 20

An enzyme that digests protein. This
reaction involves the addition of water
molecules, so it is an example of hydrolysis.
Proteases are important digestive enzymes in
animals, but they are also found in many
microorganisms and in seeds. When a seed
germinates, proteases break down proteins in
the food store to give amino acids. These amino
acids can be used to make new proteins in the
developing seedling.