Unit 1 - section 5

Question 1

What are 3 things that allow coordination to be achieved in multicellular organisms?

Answer 1

Signalling molecules
Receptors
Responses

Question 2

What is the basic role of signalling molecules, receptors and responses in coordination?

Answer 2

Signalling molecules - molecules that bind to specific receptors
Receptors - protein with binding site for specific signal molecule
Responses - occur due to an alteration of receptor conformation

Question 3

What is the effect of a signal molecule binding to a receptor?

Answer 3

Changes the conformation of the receptor. This can alter the response of the cell

Question 4

What is the significance of multicellular organisms containing many different cell types in the production, receipt and response to signals?

Answer 4

Different cell types produce specific signals which can only be detected and responded to by cells with the specific receptor. In a multicellular organism different cell types may show a tissue specific response to the same signal (two cells can respond differently to same signal)

Question 5

Where are the receptors of hydrophobic signals found?

Answer 5

Within the cells or even within the nucleus of a cell

Question 6

How do hydrophobic signals cross the membrane?

Answer 6

Can easily pass through the phospholipid membrane due to their hydrophobic nature

Question 7

What are 2 example of hydrophobic signalling molecules?

Answer 7

Thyroxine

Steroid hormones

Question 8

What is a transcription factor?

Answer 8

A protein which binds to DNA and controls rate of transcription. Can enhance or block the binding of RNA polymerase to specific genes which controls whether the gene is transcribed or not

Question 9

How are thyroid hormones used to control the transcription of the sodium potassium pump?

Answer 9

Thyroid hormone receptor protein binds to DNA in the absence of thyroxine and inhibits transcription of the gene for the sodium potassium pump. When thyroxine binds to the receptor protein, conformational change prevents the protein binding to the DNA and transcription of the gene for the sodium potassium pump can begin, raising metabolic rate

Question 10

What is the type of receptor protein that steroid hormones bind to?

Answer 10

Transcription factor proteins

Question 11

How do steroid hormones regulate transcription?

Answer 11

Only once the steroid hormone has bound to the receptor can the transcription factor bind to gene regulatory sequences of DNA for transcription to occur

Question 12

Where are receptors for hydrophilic signals located?

Answer 12

On the cell surface

Question 13

Give 2 examples of hydrophilic signalling molecules

Answer 13

Peptide hormones

Neurotransmitters

Question 14

What are the 3 stages in communication?

Answer 14

Reception - signal molecule binds to the receptor protein
Transduction - conformational change of a protein followed by the activation of other molecules and amplification of the signal
Response - activation of some other cellular response eg transcription, movement of cytoskeleton

Question 15

What is the effect of the binding of a signal molecule to a receptor?

Answer 15

A conformational change

Question 16

Do hydrophilic signal molecules enter the cell?

Answer 16

Does not enter the cell, instead it is transduced across the membrane

Question 17

What are 2 possible outcomes of hydrophilic signals being transduced?

Answer 17

Cascades of G-proteins

Phosphorylation by kinase

Question 18

How is a signal transduced using G-protein linked receptors?

Answer 18

Signal molecule binds to a receptor and the receptor changes conformation
Causes GDP to be replaced with GTP which activates the G-protein
This activates another enzyme which generates a cellular response

Question 19

How is a signal transduced using phosphorylation?

Answer 19

Ligand binds to receptor tyrosine kinases (RTKs)
Causes amino acids on the receptor to become phosphorylated resulting in conformational change in receptor
Activating the kinase domains in the receptor and phosphorylating downstream cytoplasmic molecules resulting in various cellular responses

Question 20

What type of signalling molecule is insulin

Answer 20

Hydrophilic signal molecule

Question 21

Where are insulin receptors found?

Answer 21

Surface of the cell

Question 22

What triggers the recruitment of GLUT4 glucose transporter to the cell membrane?

Answer 22

The binding of insulin to its receptor

Question 23

What is the name of the glucose transporter?

Answer 23

GLUT4

Question 24

Name 2 cell types that contain GLUT4?

Answer 24

Fat cells

Muscle cells

Question 25

What is the function of glucose transporter?

Answer 25

Allow glucose to pass across the plasma and enter the cell

Question 26

What condition is caused when insulin is not produced?

Answer 26

Type 1 diabetes

Question 27

What condition is caused by receptors of insulin failing to respond?

Answer 27

Type 2 diabetes

Question 28

What is the main cause of type 2 diabetes?

Answer 28

Obesity

Question 29

Why is exercise used to treat type 2 diabetes?

Answer 29

Exercise triggers recruitment of GLUT4 so can improve uptake of glucose to fat and muscle cells in subjects with type 2 diabetes

Question 30

What does the up take of glucose depend on?

Answer 30

Insulin being present

Question 31

What type of signal molecule is ADH?

Answer 31

Hydrophilic signalling molecule

Question 32

Where are ADH receptors located?

Answer 32

Collecting duct of the kidney

Question 33

How does ADH recruit water transporter?

Answer 33

ADH binds to its receptors on the cells collecting ducts causing a cell transduction process which results results in the recruitment of channel protein aquaporin 2 to the membrane of cells

Question 34

Name the water transporter

Answer 34

Aquaporin 2

Question 35

What is the function of aquaporin 2?

Answer 35

Provides a highly efficient route for water to move across membranes.
Recruitment of aquaporin 2 allows control of water balance in terrestrial vertebrates

Question 36

What condition results from failure to produce ADH/ insensitivity of receptor?

Answer 36

Diabetes insipidus