Hydrophobic And Hydrophilic Signals

Question 1

How do multicellular organisms signal between cells

Answer 1

By using extracellular signalling molecules

Question 2

What are examples of extracellular signalling molecules

Answer 2

• Steroid hormones (oestrogen + testosterone)
• Peptide hormones
• neurotransmitters

Question 3

What are receptor molecules of target cells - what are receptors

Answer 3

Proteins with binding site for specific signal molecule

Question 4

What initiates a response within a cell

Answer 4

Binding which changes the conformation of the receptor

Question 5

What type of response would show in a multicellular organism

Answer 5

Tissue-specific response to same signal

Question 6

What can hydrophobic signals do

Answer 6

Diffuse directly through phospholipid bilayer of membrane and bind to intracellular receptors

Question 7

What are the receptors for hydrophobic signalling molecules

Answer 7

Transcription factors

Question 8

What are transcription factors

Answer 8

Proteins which when bound to DNA can either inhibit or initiate transcription

Question 9

Examples of hydrophobic signalling molecules

Answer 9

• oestrogen

- testosterone

Question 10

What do steroid hormones bind to

Answer 10

Specific receptors in the cytosol or nucleus

Question 11

What are hormone response elements (HREs)

Answer 11

HREs are what hormone-receptor complexes binds to on specific DNA sequences

Question 12

What does binding at hormone response elements (HREs) cause

Answer 12

• It can influence rate of transcription

- affects gene expression

Question 13

Hydrophilic signalling

Answer 13

Hydrophobic signalling molecules bind to transmembrane receptors and do not enter cytosol

Question 14

What are examples of hydrophilic signalling molecules

Answer 14

• peptide hormones

- neurotransmitters

Question 15

When do transmembrane receptors change conformation

Answer 15

When ligand binds to the extracellular face and the signal is transduced across the plasma membrane

Question 16

How do transmembrane receptors act as signal transducers

Answer 16

By converting the extracellular ligand-binding event into intracellular signals —> alters behaviour of cell

Question 17

Function of G-proteins

Answer 17

G-proteins relay signals from activated receptors to target proteins like enzymes and ion Channels

Question 18

What do transduced hydrophilic signals involve

Answer 18

Often involve G-proteins or cascades of phosphorylation by kinase enzymes

Question 19

What do phosphorylation cascades allow

Answer 19

Allow for more than one intracellular signalling pathway to be activated

Question 20

What is a phosphorylation cascade

Answer 20

Involves a series of events with one kinase activating the next in sequence

Question 21

What is the result of the peptide hormone insulin binding to receptor

Answer 21

Results in intracellular cascade -> triggers recruitment of GLUT4 glucose transporter proteins to cell membrane of fat and muscle cells

Question 22

Causes of diabetes Mellitus

Answer 22

• Type 1 - failure to produce insulin

- type 2 - loss of receptor function and sensitivity (linked with obesity)

Question 23

What triggers the recruitment of GLUT4

Answer 23

Exercise which improves uptake of glucose to fat and muscle cells (type 2)