Lecture 1 - Introduction to cell regulation

Question 1

Four ways cellular activity is regulated (4)

Answer 1

Receptors
Ion channels
Transporters
Enzymes

Question 2

Ways in which a cell can cause a response in another (4)

Answer 2

Electrical

• Spread electrical activity through low resistant gap junctions.
• Endothelial cells, cardiac myocytes, epithelial cells.

Chemical synapses

• Release of chemical which influences another cell.
• Neurotransmitters

Question 3

Different types of signalling (4)

Answer 3

Paracrine: Chemical released by one cell. Localised effect.
Endocrine: Chemical from one cell into bloodstream carried to another cell where it influences cellular activity.
Synaptic: Localised synaptic signalling where chemicals is released over gap (synaptic gap)
Autocrine: Influences its own activity.

Question 4

Types of receptors (4)

Answer 4

Ligand gated - superfast (1/1000th of a second).
G Protein coupled - slower than ligand faster than tyrosine.
Tyrosine kinase linked - slower than G
Nuclear/Steroidal - found in cytosol.

Question 5

Types of ion channels (3)

Answer 5

Ligand gates
Voltage gated
Proteinaceous pores
Create an aqueous pathway through fatty lipid membrane bilayer.

Question 7

Ion channels - Voltage gated - Ca2+ channel (3)

Answer 7

Dihydropyridines
e.g. nifedipine
Anti hypertensives
Block these = less Ca2+ influx

Question 8

Ion channels - Voltage gated - Na+ channel (2)

Answer 8

Local anaesthetics
e.g. lignocaine or procainamide
Less negative - depolarised Na+ channels open.
Block these = pain relief.

Question 8

Ion channels - Voltage gated - K+/Cl- channel (2)

Answer 8

Anti-arrhythmic agents

e.g. vernakalant

Question 9

Ion channels - Real life examples (2)

Answer 9

Cystic fibrosis ion channel CFTR –> Cl- channel found in epithelia and digestive tracts = increased by cAMP dependent kinases.
Cardiac myocytes in atria have different complement of ion channels to cardiac myocytes in ventricles. Drug companies can then use this difference to create drugs that only target arrythmias in atria (not affecting ventricles).

Question 11

Transporters - Type 1 (5)

Answer 11

Exchangers

• One molecule is exchnaged for another.
• NA+/K+ ATPase.
• Ouabain and Digoxin inhibit above.
• Drugs prescribed for heart failure, cardiac glycosides.
• Digoxin increases cardiac contraction.

Question 12

Transporters - Type 2 (2)

Answer 12

Symporters - Come in together (2 at a time)

Na+/glucose transporter.

Question 13

Transporters - Type 3 (4)

Answer 13

Antiporters

• Move in opposite directions (2 at a time).
• Carrying a solute into or out of the cell, using the electrochemical gradient of the second solute, which is travelling in the opposite direction. In other words, solute A will travel down a concentration gradient into the cell, releasing energy which is harvested by solute B and used as a driving force to be pumped out of the cell in the opposite direction, but within the same transporter.
• Na+/Ca+ antiporter, driven by the electrochemical gradient of Na+ across the membrane. Cardiac myocyte.
• Sodium/Potassium isn’t one as they both travel against concentration gradient.

Question 13

Roles of calcium (3) (1)

Answer 13

Produces contraction.
Stimulated some enzymes.
Causes cellular apoptosis.

If levels are too high, various enzymes are activated, get DNA damage and cell membrane starts to deform.

Question 14

Same molecule can have different effects on the body/Signalling molecules are versatile and induce differential responses (5)

Answer 14

Acetylcholine
Main transmitter in PNS.
Increases saliva production, salivary gland.
Decreased rate and force of attraction of the heart.
Contraction of skeletal muscle.