Cell signalling

Question 1

explain Hydrophobic signals Movement through cell membrane

Answer 1

Diffuse directly through phospholipid bilayer

Binds to intracellular receptors in cytoplasm on target tissue

Question 2

Give some examples of Hydrophobic Signals

Answer 2

Usually hormones (oestrogen, testosterone , steroids)

Question 3

What is a transcription factor

Answer 3

Hydrophobic Signals bind to intracellular receptors it forms a hormone receptor complex

–> binds to DNA to either inhibit or stimulate transcription

Question 4

What is the hormone response element?

Answer 4

The site that the hormone receptor (transcription factor) binds to.

Question 5

Does Na/K Pump use energy?

Answer 5

yes
From the hydrolysis of ALP
- phosphate from ATP breaks off and is used to cause the conformational change!

Question 6

What is an active transport?

Answer 6

because ions are being transported against a steep concentration (from low to high – uphill!)
Example: NA/K pump

Question 7

Explain the process of NA/K pump

Answer 7

The pump (protein!) has a high affinity for Na+ ions inside the cell therefore binding occurs.
Phosphate attaches to pump (protein!). Phosphorylation (adding a phosphate) by ATP causes the conformation of the protein to change.
The affinity for Na+ ions decreases resulting in 3 Na+ being released outside of the cell
The pump (protein) now has high affinity for K+ ions outside the cell and binding occurs
Dephosphorylation (removal of phosphate) occurs which causes the conformation of the protein to change
2 K+ ions are taken into the cell and the affinity returns to the start

Question 8

What is an action potential?

Answer 8

when the neuron is firing – it is a wave of electrical excitation. When an action potential reaches the end of a neuron it causes vesicles containing neurotransmitters to be released. This then stimulates a response.

Question 9

Explain the process of Action potential of a neurone

Answer 9

A neurotransmitter binds to a receptor. If there is enough it will open a voltage-gated Na+ channel, allowing Na+ ions to flood in. A large and rapid change in membrane potential has happened . This is depolarisation –less negative value inside the neuron.
After opening, the Na+ channel becomes inactivated.
Voltage-gated K+ channels open, allowing K+ to move out of the neuron to restore the resting membrane potential. This is repolarisation.
This removes positive charges from the inside of the cell and starts to bring about the resting potential

Question 10

how is the Membrane gradient re-stabilised?

Answer 10

By the Na/K pump because they transport excess ions in and out of the cell

Question 11

What is resting membrane potential?

Answer 11

Depolarised state of a membrane, ready to undergo another Action potential wave

Question 12

Glucose transport and Na/K pump

Answer 12

The gradient created by the Na+ / K+ pump helps drive the active transport of glucose through glucose symport protein(move the glucose!)

Question 13

Where does the glucose transport take place?

Answer 13

Happens in the intestinal epithelial cells (small intestine) moving glucose into the blood stream

Question 14

Explain Na and Glucose movement

Answer 14

Na+ moves into the cell down its concentration gradient and glucose is pumped into the cell against its concentration gradient

So by continually pumping Na+ out of the cell allows glucose symport protein to move glucose into the blood stream