Regulating Flow, Biological Signalling + Calcium

Question 1

What 2 factors does Passive Diffusion depend on?

Rank the Permeability levels of

• Hydrophobic
• Small uncharged
• Large uncharged
• Ions

Answer 1

Ionic gradient + Permeability

Most permeable - Hydrophobic
Highly Permeable - Small Uncharged
Low Permeability- Large Uncharged
Impermeable- Ions

Question 2

3 roles of transport processes

Answer 2

• Maintain pH and ion concentrations
• Regulate Cell volume
• Excretion of waste and toxic products

Question 3

What are the Intra AND Extracellular concentrations for

1. Ca
2. K
3. Cl
4. Na

Answer 3

Ca: 1.5 mM outside, 0.1 microMolar inside
K: 4mM outside, 155mM Inside
Cl: 123mM outside, 4.2 mM Inside
Na: 145mM outside, 12nM Inside

Question 4

How does PMCA work?

Answer 4

Hydrolyses ATP to transport Ca2+ out of the cell

Question 5

How does the Na-K Pump work?

Answer 5

ATP Hydrolysed
3Na+ are transported out
2K+ are taken into cell

Question 6

How does the Na-Ca-Exchanger (NCX) work?

What effect does depolarisation have on this process?

Answer 6

• Uses Na gradient from Na-K Pump
• 3Na into cell, 1Ca out of cell

Activity reversed, as NCX depends on membrane potential

Question 7

How does Ischaemia affect the NCX exchanger?

Answer 7

• ATP is depleted, so Na-K Pump stops and Na gathers in cell

- Activity is reversed, so Na is moved out of cell and Ca is moved into cell, which is toxic

Question 8

How does the Na-H-Exchanger (NHE) work?

Answer 8

• Uses Na gradient from Na-K Pump

- One Na moves into cell, One H moved out of cell

Question 9

How is Na used to move Glucose into the cell?

Answer 9

Na gradient
Causes Na to move into cell, along with Glucose
Through a Symport

Question 10

Which 3 co-transporters are involved in regulating intracellular pH
How do they work?

Answer 10

• NHE ( Na in, H out)
• NBC ( Na, HCO3- in. H, Cl- out) Alkanises the cell
• Anion Excanger (HCO3- out, Cl- in) acidifies the cell

Question 11

At the Set Point pH, which two transporters have equal activity?
Which transporter has a higher activity, what is the effect on pH of cell?

Answer 11

NHE and AE

NBC works more, Alkanises the cell

Question 12

What are 4 process involved in increasing [Ca] inside the cell?

Answer 12

• Ligand Gated Calcium Channels
• Voltage Operated Calcium Channels
• IP3R open when binded to IP3, allowing Ca to leave SR/ER to enter cytoplasm
• CICR/ Ryanodine receptors detect high cytoplasmic Ca, allowing more Ca to enter cytoplasm, from SR/ER

Question 13

How does SERCA work?

Answer 13

Uses ATP to release Ca into cytoplasm

Question 14

What is the [Ca] inside the SR/ ER?

Answer 14

0.2 mMolar

Question 15

Which 3 factors oppose an increase in Cytoplasmic Calcium?

Answer 15

• Impermeability of Membrane to Ca2+
• Ca transporters, proteins move Ca out of cytoplasm
• Ca buffer proteins (Decrease Free Ca Level)

Question 16

How do Nuclear/ Intracellular Receptors work?

Answer 16

Hydrophobic ligand binds to receptor
Ligand-receptor complex binds to gene transcription factor
Activates/ inactivates a gene/ set of genes

Question 17

Explain how a Kinase-linked receptor works

Answer 17

1. Agonist binds to a receptor, activating Tyrose Kinase
2. Autophosphorylation: TK Phosphorylates the adjacent chain of same molecule
3. Enzymes bind to phosphorylated TK and gets phosphorylated itself

Question 18

Compare Paracrine, Autocrine, Endocrine Signalling

Answer 18

Para: Signalling molecule affects adjacent cells
Auto: Signalling molecule affects cell that it was released from
Endo: Signalling molecule released directly into blood to distant target cells