Signalling Molecules

Question 1

Nervous communication;

Answer 1

• transmission fast
• response more rapid
• impulse travels electronically along axons and chemically across synapses and transmitter substances.
• response is specific in certain muscle or gland.
• response is short lived.

Question 2

Endocrine communication;

Answer 2

• transmission is slow
• hormonal response is slower
• chemical communication as they travel in blood.
• response is widespread over the body, but only at target organs or cells.
• response is long-lasting/prolonged.

Question 3

How are messages passed on by neurone?

Answer 3

• nerve impulse; wave of electrical charge that travels the length of the neurone membrane.
• stimulated by a change to sensory cell, or by another neurone on nerve pathway.
• when action potential reaches synapse, neurotransmitters diffuse across the gap to stimulate the next nerve.

Question 4

Neurotransmitters?

Answer 4

Produced by neutrons and comprise the synapse. Serotonin

Question 5

Receptor

Answer 5

A specialised cell that detects a stimulus. As a result a nerve impulse may be generated or a hormone produced.

Question 6

Signal transduction

Answer 6

A process by which a cell converts one kind of signal or stumble into another.
Usually involves ordered sequences of biochemical reactions inside the cell, carried out by enzymes, activated by second messengers, resulting in signal transduction pathway.

Question 7

Plant hormones;

Answer 7

• auxin
• gibberellins
• Ethylene
• cytokinin
• abscisic acid

Question 8

Auxin;

Answer 8

Hormones involved in plant- cell elongation, apical dominance and rooting. Eg, indoleacetic acid (IAA)

Question 9

Gibberellins;

Answer 9

Stimulates elongation growth. Spraying a plant with such will usually cause the plant to grow to a larger than expected height.

Question 10

Ethylene.

Answer 10

Responsible for ripening fruits. A gas at room temp. Diffuses easily through the air from one plant to another.

Question 11

Cytokinins;

Answer 11

Promote cell division in plants. Produced in developing shoots, roots, fruits and seeds of plants. Important in culturing of plant tissues in the laboratory.

Question 12

Abscisic acid.

Answer 12

Abscisic acid or ABA generally inhibits other hormones.
Thought to promote abscission.
Causes closure of a plants stomata in response to drought.

Question 13

Tropism

Answer 13

Phototropism, movement of plant in response to light coming from one particular direction. Away- negative, towards- positive.

Gravitropism, plant growth response to gravity.