1.5 COMMUNICATION WITHIN MULTICELLULAR ORGANISMS

Question 1

How do multicelluar organisms achieve coordination?

Answer 1

Through extracellular signalling molecules, receptors and responses

Question 2

What are receptor molecules?

Answer 2

Proteins in target cells with a binding site for a specific molecule

Question 3

What effect does binding have on receptor molecules?

Answer 3

Conformational change

Question 4

What is the result of a conformational change of a receptor molecule?

Answer 4

It alters the response of the cell

Question 5

How is extracellular signalling specific?

Answer 5

Different cells produce specific signal molecules which can only be detected and responded to by cells with the specific receptors

Question 6

In which type of organism is a tissue-specific response to the same signal possible?

Answer 6

Multicellular organisms

Question 7

Where can receptors for hydrophobic signalling molecules be found?

Answer 7

In the cytoplasm or nucleus of their target cell

Question 8

How is it possible that hydrophobic signalling molecules have receptors inside of the target cell?

Answer 8

They are lipid soluble

Question 9

What does lipid soluble mean?

Answer 9

The substance can move through the plasma membrane

Question 10

What can hydrophobic signalling molecules directly influence?

Answer 10

Transcription of genes

Question 11

Give two examples of types of hydrophobic signalling molecules.

Answer 11

Thyroxine, steroid hormones

Question 12

What is thyroxine?

Answer 12

A thyroid hormone

Question 13

What does thyroxine hormone receptor bind to in the absence of thyroxine?

Answer 13

DNA

Question 14

What is the result of thyroxine hormone receptor binding to DNA?

Answer 14

Inhibition of transcription of Na/KATPase gene

Question 15

What is the result of thyroxine binding to its receptor?

Answer 15

Conformational change of thyroxine hormone receptor

Question 16

What is the result of the conformational change to thyroxine hormone receptor?

Answer 16

Thyroxine hormone receptor can no longer bind to DNA

Question 17

What happens when thyroxine hormone receptor cannot bind to DNA?

Answer 17

Transcription of Na/KATPase gene, increasing metabolic rate

Question 18

What is the receptor protein for steroid hormones?

Answer 18

Transcription factor

Question 19

What is the result of a steroid hormone binding to a transcription factor?

Answer 19

Transcription factor can bind to gene regulatory sequence of DNA

Question 20

What happens when a transcription factor binds to a gene regulatory sequence?

Answer 20

Transcription occurs

Question 21

Where are receptors for hydrophilic signalling molecules found?

Answer 21

At the surface of the cell

Question 22

Give two examples of hydrophilic signalling molecules.

Answer 22

Peptide hormones, neurotransmitters

Question 23

What happens to transmembrane receptors when a ligand binds outside of the cell?

Answer 23

Transmembrane receptors undergo conformational change

Question 24

How is a hydrophilic signal transmitted across the membrane?

Answer 24

Signal transduction

Question 25

What does signal transduction often involve?

Answer 25

Cascades of G proteins or phosphorylation by kinase enzymes

Question 26

Name the two types of diabetes.

Answer 26

Diabetes mellitus and diabetes insipidus

Question 27

Name the two types of peptide hormone.

Answer 27

Insulin and ADH

Question 28

Where are receptors for insulin located?

Answer 28

Fat and muscle cells

Question 29

What is the result of insulin binding to its receptor?

Answer 29

Recruitment of GLUT 4 glucose transporters triggered

Question 30

Where are GLUT 4 glucose transporters recruited to?

Answer 30

Cell membrane of fat and muscle cells

Question 31

What do GLUT 4 glucose transporters facilitate?

Answer 31

Uptake of glucose into fat and muscle cells

Question 32

What causes type 1 diabetes?

Answer 32

Failure to produce insulin

Question 33

What causes type 2 diabetes?

Answer 33

Loss of receptor function

Question 34

Which type of diabetes (mellitus) is obesity usually associated?

Answer 34

Type 2

Question 35

Other than insulin binding, what also triggers recruitment of GLUT 4 glucose transporters?

Answer 35

Exercise

Question 36

Why is exercise recommended to sufferers of type 2 diabetes?

Answer 36

It triggers recruitment of GLUT 4 glucose transporter therefore increasing uptake of glucose to fat and muscle cells

Question 37

Where are receptors for ADH located?

Answer 37

Collecting duct of kidney

Question 38

What is the result of ADH binding to its receptor?

Answer 38

Recruitment of aquaporin 2 (AQP2)

Question 39

What does aquaporin 2 do?

Answer 39

Provides efficient route for water to move across membranes

Question 40

What does aquaporin 2 enable?

Answer 40

Control of water balance in terrestrial vertebrates

Question 41

What causes diabetes insipidus?

Answer 41

Failure to produce ADH / Insensitivity of ADH receptors