cell signal and membrane

Question 1

What does the K+/Na+ pump across the membrane?

Answer 1

K+ out of the cell (2K)

Na+ out of the cell (3Na)

Question 2

What determines the intracellular and extracellular osmolarity?

Answer 2

IC= inorganic ions and impermeable ions
EC= inorganic ions

Question 3

Intracellular pH and why?

Answer 3

7.0-7.2 because cells produce acidic by-products resulting in a slightly more acidic ICF

Question 4

What do the Na+/H+ and Cl-/HCO3- antiports transport?

Answer 4

Na+/H+= regulates ICF pH so pumps H+ out and Na+ in
Cl-/HCO3-= regulates ICF pH so pumps HCO3- out and Cl- in

Question 5

What dos the Na+/HCO3- symport transport?

Answer 5

They’re both transported into the cell

Question 6

How is intracellular Ca2+ concentration regulated (2 pumps) ?

Answer 6

Na+/Ca2+ antiports transport Ca2+ out of the cell to maintain a low ICF concentration. This reduces background noise so a signal can be heard.
Ca2+ ATPase pumps also perform the same action but pump the calcium into ER/Mitochondria

Question 7

Resting membrane potential equation

Answer 7

Nernst equation (look to lecture 2 for diagram)

Question 8

Types of chemical cell signals

Answer 8

Paracrine: affects cells in the immediate vicinity of the cell that secreted it
Autocrine: the messenger also affects the cell that secreted it
Endocrine: Chemical messengers enter the blood and travel around the entire body

Question 9

What are ligand agonists and antagonists?

Answer 9

Agonist are chemical that binds to the receptor, activating it naturally
Antagonists are chemicals that bind to the receptors, preventing the agonist from initiating a response.

Question 10

What’s the difference between a ligand and agonist?

Answer 10

Ligand= occurs naturally
Agonist= natural or unnatural

Question 11

How are Receptor-Ion channels activated?

Answer 11

Agonist binds to receptor causing a conformational change, opening the channel

Question 12

What happens when a receptor ion channel is activated?

Answer 12

Ions diffuse across the membrane initiating depolarisation, which in turn activates voltage-gated channels.

Question 13

What do the majority of enzyme receptors initiate?

Answer 13

Protein Kinases to phosphorylate other proteins (autophosphorylation)
Exception: cyclase GMP has an intermediary

Question 14

What is the largest class of cellular receptor?

Answer 14

G-protein linked receptors (a.k.a 7 transmembrane receptors)

Question 15

Describe G-linked protein receptor structure.

Answer 15

3 subunits (alpha, beta and gamma) linked to a 7 alpha helix transmembrane receptor.

Question 16

Describe the G-protein mechanism when activated by the receptor

Answer 16

1) Alpha subunit exchanges GDP for GTP.
2) The alpha subunit dissociates from beta and gamma; they both target other proteins.
3) GTP hydrolysed to GDP and the alpha subunit reforms with the beta and gamma subunits, ready to be activated again

Question 17

How is adenyl cyclase activated (from cyclic AMP)?

Answer 17

G-protein alpha subunit activates it

Question 18

What does adenyl cyclase convert and what does the product activate?

Answer 18

Converts ATP to cyclic AMP.

Cyclic AMP activates Protein Kinase A (PKA).

Question 19

What breaks down cAMP and what is the product?

Answer 19

Phosphodiesterase and AMP

Question 20

What process do G-protein linked receptors initiate?

Answer 20

Amplifying signalling cascade

Question 21

Which type of G-protein is involved in the inositol triphosphate (IP3) signalling cascade?

Answer 21

Gq

Question 22

What does Gq activate, and what action does this product perform?

Answer 22

Gq activates phospholipase C.

Phospholipase C converts PIP2 into inositol triphosphate and DAG.

Question 23

What do IP3 and Diacylglycerol activate, respectively?

Answer 23

IP3: Endoplasmic reticulum calcium channels.
DAG: Protein kinase C (PKC).

Question 24

What does PKC activate?

Answer 24

Protein Kinase C activates cellular Ca2+ receptors and channels, causing calcium ions to enter the cell

Question 25

Explain the mechanism by which intracellular messengers effectuate a response.

Answer 25

1) Lipid soluble so diffuse into the cell.
2) Bind to a receptor to form a complex.
3) The complex is transported into the nucleus.
4) Complex binds to release a DNA response factor.
5) The element alters DNA transcription.