1.4 Communication And Signalling

Question 1

Describe how hydrophobic signal molecules can enter cells

Answer 1

Pass directly through phospholipid bilayer

Question 2

Describe how hydrophobic signal molecules can effect gene expression

Answer 2

Enter cell and bind with receptor in cytosol/ nucleus
Hormone-receptor complex binds to DNA in nucleus
At hormone response elements (HRE)
Affect transcription of genes

Question 3

Describe how hydrophilic molecules act specifically

Answer 3

Signal molecule/hormone acts as ligand

Binds to complementary/specific receptor in cell membrane

Question 4

Hormones are a type of what?

Answer 4

Signal molecule

Question 5

Describe the process of signal transduction

Answer 5

When signal bound, receptor causes G-protein/kinase

Activates cellular response

Question 6

Explain how insulin can cause a decrease in blood glucose concentration

Answer 6

Insulin binds to receptor
Phosphorylation cascade
GLU4 vesicles recruited into membrane
GLUT4s allow glucose into cell

Question 7

Membrane polarity refers to what?

Answer 7

The degree of difference in charge on one side of the membrane compared to the other.

Question 8

What does the restoration of the resting potential allow?

Answer 8

The system to be sensitive again and respond to new signals.

Question 9

Describe how action potential is achieved in neurons

Answer 9

Neurotransmitter binds to receptor
Sodium channels open
Change in potential opens voltage-gated sodium channels
Further sodium entry takes membrane to threshold

Question 10

Describe how the resting potential is restored following the passage of an action potential

Answer 10

Sodium channels close
Potassium channels open and potassium ions leave
Sodium-potassium pump is activated
Pump causes net loss of sodium ions

Question 11

Describe the structure of rhodopsin

Answer 11

Opsin that is bound to retinal

Question 12

Describe how a photon of light has its effect amplified in a rod cell to produce a nervous impulse

Answer 12

Photon affects conformation of rhodopsin to excited state
Cascade of hundreds of transducins
Activate PDE
PDE breaks down cyclic GMP/cGMP
Reduction in cGMP closes ion channels and impulse fires

Question 13

Name the components of a rhodopsin molecule from a vertebrate eye

Answer 13

Retinal and opsin

Question 14

When a photon of light strikes a rhodopsin molecule, transducin proteins are activated. Describe your effects of activated transducins.

Answer 14

They activate a cascade of phosphodieterase (PDE) molecules

Which breakdown cyclic GMP/cGMP molecules

Question 15

Describe the effects of reduced levels of cyclic GMP on sodium ion channels in the rod cell

Answer 15

Sodium ion channels close

Question 16

Rod cells amplify the effects of light.

State why this is an advantage to vertebrates.

Answer 16

It allows vision in dim light/allows nocturnal/crepuscular activities/hunting/foraging

Question 17

State how the photoreceptor molecules of cone cells differ from those in rod cells.

Answer 17

Different opsins

Question 18

What are is opsin?

Answer 18

A light sensitive protein molecule found in the animal kingdom.

Question 19

Describe how voltage-gated channels are activated and their effects on the resting potential.

Answer 19

Increased positive change inside membrane opens voltage-gated channels,
Allows more sodium ions to enter.

Question 20

Explain why it is important that the neuron is restored to resting potential following the transmission of a nervous impulse.

Answer 20

Allows the system/neuron to remain sensitive to further stimulation.

Question 21

Give account of the role of insulin in the decrease in glucose concentration in blood.

Answer 21

Insulin binds with receptor
Triggers a cascade of phosphorylation
GLUT containing vesicles are recruited into membrane
Glucose enters through the GLUT from bloodstream

Question 22

Give an account of hydrophobic cell signalling

Answer 22

Hydrophobic signal/steroid hormone
Enters cell through phospholipid layer
Combines with receptor in cytosol/nucleus
Hormone receptor binds with hormone response elements (HRE) on DNA
Gene expression affected