KA5 - Communication within Multicellular Organisms

Question 1

How do multicellular organisms achieve coordination?

Answer 1

Through extracellular signalling molecules, receptors and responses

Question 2

What are receptor molecules of target cells?

Answer 2

Proteins with a binding site for a specific signal molecule

Question 3

What does binding change?

Answer 3

The conformation of the receptor and this can alter the response of the cell

Question 4

Different cell types produce specific signals which can…

Answer 4

Only be detected and responded to by cells with the specific receptor

Question 5

In a multicellular organism, different cell types may show… ?

Answer 5

A tissue specific response to the same signal

Question 6

What do hydrophobic signalling molecules include?

Answer 6

The thyroid hormone thyroxine and steroid hormones

Question 7

What can hydrophobic signalling molecules influence?

Answer 7

Directly influence transcription of genes

Question 8

Hydrophobic signalling molecules can diffuse through…?

Answer 8

Membranes so their receptor molecules can be within the nucleus

Question 9

What are the receptor proteins for steroid hormones known as?

Answer 9

Transcription factors

Question 10

Only once the hormone signal has bound to the receptor can… happen?

Answer 10

The transcription factor bind to gene regulatory sequences of DNA for transcription to occur

Question 11

What do hydrophilic signalling molecules include?

Answer 11

Peptide hormones and neurotransmitters

Question 12

What do hydrophilic signals require?

Answer 12

Receptor molecules to be at the membrane of the cell

Question 13

When do transmembrane receptors change conformation? What happens?

Answer 13

When the ligand binds on the cell surface;

The signal molecule does not enter the cell but the signal is transduced across the membrane of the cell

Question 14

What do transduced hydrophilic signals often involve?

Answer 14

Cascades of G-proteins or phosphorylation by kinase enzymes

Question 15

How can the type 1 diabetes be caused?

Answer 15

By failure to produce insulin

Question 16

How can type 2 diabetes be caused?

Answer 16

Loss of receptor function

Question 17

What is type 2 diabetes generally associated with? How can this be helped?

Answer 17

Generally associated with obesity

Exercise also triggers recruitment of GLUT4 so can improve uptake if glucose to fat and muscle cells in subject with type 2

Question 18

Binding of peptide hormone ADH to its receptor in collecting duct of kidney triggers…?

Answer 18

Recruitment of channel protein aquaporin 2 (AQP2)

Question 19

What do aquaporins provide?

Answer 19

A highly efficient route for water to move across membranes

Question 20

What does recruitment of AQP2 allow for?

Answer 20

Control of water balance in terrestrial vertebrates

Question 21

What does failure to produce ADH or insensitivity of its receptor result it?

Answer 21

Diabetes insipidus

Question 22

What does binding of the peptide hormone insulin to its receptor trigger?

Answer 22

Recruitment of GLUT4 glucose transporter to the cell membrane of fat and muscle cells

Question 23

When do thyroid hormone receptor protein bind to DNA? What does it do?

Answer 23

In the absence of thyroxine and inhibits transcription of the gene for Na/KATPASE

Question 24

When thyroxine binds to the receptor protein what happens?

Answer 24

Conformational change prevents protein binding to the DNA and transcription of the gene for Na/KATPase can begin raising metabolic rate