7.6 Improving on nature

Question 1

Hormone

Answer 1

A substance that acts as a chemical
messenger. Hormones are secreted into the
blood by endocrine glands. The blood transports
them to particular organs where they help to
regulate body processes. The hormone insulin,
for example, is secreted by the pancreas. It
travels in the blood to various organs including
the liver. It is important in helping the cells of
the liver to control the concentration of glucose
in the blood.

Question 2

Pituitary gland

Answer 2

An endocrine gland situated at
the base of brain. It releases a number of
hormones. These include growth hormone,
follicle stimulating hormone and antidiuretic
hormone.

Question 3

Endocrine

Answer 3

A gland that secretes hormones
directly into the blood is called an endocrine gland. Glands are organs which secrete
particular substances. The pancreas is an
endocrine gland because it secretes the hormone
insulin into the blood. It is also an exocrine
gland because it secretes digestive enzymes into
a duct which takes them into the intestine.

Question 4

Follicle stimulating hormone, FSH

Answer 4

A hormone
produced by the pituitary gland. In female
mammals it is produced during the first half of
the reproductive cycle and stimulates one or
more immature follicles in the ovary to develop.
Follicle stimulating hormone is also produced in
males where it is essential for sperm formation.

Question 5

Thyroxine

Answer 5

A hormone secreted by the thyroid
gland in the neck. It plays an important part in
controlling metabolic rate. It is also involved in
the control of body temperature. If the body
temperature falls, more thyroxine is released.
Thyroxine causes some of the energy released in
the electron transport chain to raise the
temperature of the surroundings rather than
going to form ATP.

Question 6

Testosterone

Answer 6

A male sex hormone. Testosterone
is a steroid secreted by cells in the testis. It has
several effects on the body, including turning the
developing organs of an embryo into those of a
male. It also brings about changes to the
skeleton and muscles. Athletes may use
testosterone and synthetic anabolic steroids
such as nandrolone to increase the size and
strength of muscles.

Question 7

Transcription factor

Answer 7

A protein that binds with
DNA to initiate transcription. The transcription
factors, along with RNA polymerase, have the
effect of ‘switching on’ a gene.

Question 8

Transcription initiation complex

Answer 8

Transcription
factors and RNA polymerase bind with DNA
when a gene is switched on, just before
transcription. The combination of transcription
factors and RNA polymerase is called a
transcription initiation complex because it
triggers transcription.

Question 9

Erythropoietin, EPO

Answer 9

A hormone, produced by
the kidney, which increases the rate of
production of red blood cells. Because this
results in an increase in the oxygen-carrying
capacity of the blood, erythropoietin is
sometimes used as a performance-enhancing
drug.

Question 10

Anabolic, Anabolic steroid

Answer 10

An anabolic reaction
is a chemical reaction in which smaller
molecules combine together to produce larger
ones. Examples of anabolic reactions include
photosynthesis and protein synthesis.
Testosterone is described as an anabolic steroid
because it is a steroid hormone that builds up
substances such as muscle proteins, leading to
an increase in the size and strength of muscle.

Question 11

Steroid

Answer 11

Steroids are lipids that do not contain
fatty acids. Lipids are a group of substances
which do not dissolve in water but are soluble in
organic solvents such as ethanol. Cholesterol is
a very important steroid. It is found in cell
membranes and can be converted into other
biologically important steroids such as the sex
hormones oestrogen and testosterone.