4a + 4b + 4c: Communication and Signalling

Question 1

Multicellular organisms signal between cells using…

Answer 1

extracellular signaling molecules and complementary receptor proteins.

Question 2

Examples of extracellular signaling molecules

Answer 2

• steroid hormones (eg testosterone, estrogen, progesterone)
• peptide hormones (eg insulin, glucagon)
• neurotransmitters (eg serotonin, dopamine)

Question 3

Receptor molecules of target cells are proteins with…

Answer 3

a binding site for a specific signal molecule.

Binding causes a conformational change which leads to a response within the cell

Question 4

Why do different types of cells produce specific signal sequences

Answer 4

As they can only be detected and responded to by cells with the specific receptors.

Question 5

Why do different types of cells produce specific signal sequences

Answer 5

As they can only be detected and responded to by cells with the specific receptors.

Question 6

How do hydrophobic signals work

Answer 6

They can diffuse directly through the phospholipid bilayer of the membranes.

They can therefore bind to intracellular receptors.

(this is because the tails of the phospholipids in the membranes are also hydrophobic and allow the molecules to pass through.)

Question 7

Example of hydrophobic signaling hormone

Answer 7

Steroid hormones eg estrogen or testosterone.

Question 8

where do steroid hormones bind

Answer 8

receptors in the cytosol or nucleus.

Question 9

Receptors for hydrophobic signaling are _______

Answer 9

transcription factors.

Question 10

What are transcription factors

Answer 10

proteins that when bound to DNA can either stimulate or inhibit inhibition of transcription.

Question 11

What is the hormone receptor complex

Answer 11

when the steroid hormone binds to the specific receptors in the cytosol or nucleus

Question 12

the hormone receptor complex moves to…

Answer 12

the nucleus where it binds to specific sites on DNA and affects gene expression

Question 13

The DNA sequences that the hormone receptor complex binds to is called…

Answer 13

hormone response elements.

Question 14

What does binding of the hormone receptor complex to the hormone response element in the DNA do?

Answer 14

influences the rate of transcription

(each steroid hormone affects the gene expression of many different genes.)

Question 15

How to hydrophilic signals work?

Answer 15

Hydrophilic signalling molecules (ligand) bind to transmembrane receptors and do not enter the cytosol.

Eg peptide hormones and neurotransmitters.

Question 16

Steps in Hydrophilic signaling

Answer 16

1. Signalling molecules bind to transmembrane receptor
2. Transmembrane receptor changes conformation. The signal molecule does not enter the cell.
3. Signal is then transduced across the membrane.
4. response

Transmembrane receptors act as signal transducers by converting the extracellular ligand-binding event into intracellular signals, which altars the behaviour of the cell.

Question 17

Transduced hydrophilic signals often involve…

Answer 17

• G proteins
• cascades of phosphorylation by kinase enzymes

Question 18

How to G- proteins work

Answer 18

they relay signals from activated receptors (receptors that have bounds a signalling molecule) to target proteins such as enzymes and ion channels.

(can cause the opening and closing of ion channels)

Question 19

Cascades of phosphorylation involves…

Answer 19

a series of events with one kinase activating the next in the sequence and so on.

Question 20

Cascades of phosphorylation cans result in…

Answer 20

the phosphorylation of many proteins as a result of the original signalling event.

Question 21

Cascades of phosphorylation allows…

Answer 21

more than one signaling pathway to be activated.

Question 22

Process of insulin binding

Answer 22

1. Insulin binds to its receptor.
2. Receptor undergoes a conformational change that triggers phosphorylation of the receptor.
3. A phosphorylation cascade is started inside the cell.
4. Vesicles containing GLUT4 are transported to the cell membrane.
5. Glucose passes through the GLUT4 transporters.

Question 23

What is Type 1 diabetes

Answer 23

failure to produce (enough) insulin

Question 24

What is Type 2 diabetes

Answer 24

loss of receptor function to insulin

(generally associated with obesity. Exercise also triggers recruitment of GLUT 4 so it can greatly improve the uptake of glucose to fat and muscle cells in subjects with Type 2 diabetes)