Communication and signalling

Question 1

Identify extracellular signalling molecules (3).

Answer 1

1. Neurotransmitter
2. Steroid hormones
3. Peptide hormone

Question 2

Describe the process of hydrophobic signalling (7).

Answer 2

1. Hydrophobic signalling molecules can diffuse through the hydrophobic phospholipid bilayer.
2. Hydrophobic signalling molecules then bind to a specific receptor in the cytoplasm.
3. This creates a steroid-hormone complex.
4. This acts as a transcription factor.
5. The transcription factor will then target a specific section of DNA, known as the Hormone Response Element (HRE).
6. This then effects the rate of transcription.
7. Examples include testosterone, oestrogen, thyroxine and cortisol.

Question 3

Describe the process of hydrophilic signalling (5).

Answer 3

1. Signal molecule binds to a specific receptor on the surface of the cell.
2. This causes conformational changes in the receptor
3. Conformational changes trigger kinase activity
4. A single transduction pathway can have multiple effects.
5. Kinase activity causes a phosphylation cascade, in which one kinase actives another in the sequence.

Question 4

Discuss insulin receptor transduction (4).

Answer 4

1. Binding of insulin causes conformational changes in the receptor.
2. Conformational changes causes kinase activity.
3. Kinase activity triggers a phosphylation cascade.
4. The phosphylation cascade triggers the recruitment of GLUT4 molecules to fat and muscle cells.
5. Cells can then take glucose from the blood stream.

Question 5

Discuss the differences between Type 1 and Type 2 diabetes.

Answer 5

Type 1 diabetes is a desensitisation to insulin, where as type 2 is a failure to produce insulin.

Question 6

What can improve Type 2 diabetes?

Answer 6

Excercise.

Question 7

Describe G-Proteins (3).

Answer 7

1. A signal molecule binds to a G-protein linked receptor.
2. A G-protein is recruited where it will then become active
3. The G-protein will then trigger a response, including enzymes or ion channels in the membrane.

Question 8

What is resting potential.

Answer 8

A cellular state where there is no net flow of ions across a membrane.

Question 9

When at resting potential, discuss where there sodium and potassium ions primary lie.

Answer 9

When at resting potential there are more sodium ions in the extracellular space, and more potassium ions in the intracellular space.

Question 10

What is an action potential.

Answer 10

An action potential is a wave of electrical excitation along a neurons plasma.

Question 11

What are the two types of photoreceptors?

Answer 11

Rods - Black and White
Cones - Colour

Question 12

Discuss the composition of photoreceptor cells.

Answer 12

Photoreceptor cells are composed of opsin, which contain retinal

Question 13

Identify the location of photo receptor cells in the retina.

Answer 13

Disc area.

Question 14

Discuss the advantages of rod cells.

Answer 14

Multiple rod cells are connected by a single neuron, allowing high degrees of amplification in the presence of low light.

Question 15

How to cones function?

Answer 15

A single cone is connected to a single neuron. Cones combine different kinds of obsin to produce different photoreceptor proteins.

Question 16

Discuss light transduction

Answer 16

1. Photons stimulate rhodopsin, which is composed of 7 transmembrane rods.
2. Photo excited rhodopsin then recruits the G protein called transducin.
3. The G-protein transducin, once activated, will trigger the enzyme PDE.
4. The PDE enzyme then will then cause the hydrolisis of cGMP into GMP
5. This will trigger the cGMP gated channel to open
6. This means the action potential is no longer inhibited and is then sent to the visual centre of the brain.