Cell structures

Question 1

Give the function and an example of: A microfilament

Answer 1

Muscle contraction - Actin

Cytokinesis

Question 2

Intermediate filaments

Answer 2

Matintain cell structure -

Vimenttin, desmin, neurofilaments, cytokeratin

Question 3

Microtubules

Answer 3

Movement and cell division

Cilia, flagella, mitotic spindles, centrioles,

Question 4

Name some immunohistochemical stains for intermediate filaments

Answer 4

Vimentin - Connective tissue stain

Desmin - Muscle stain

GFAP - Neuroglial stain

Question 5

Describe the Microtubule structure.

Answer 5

Made up of heterodimers of alpha and beta tubulin. each dimer has 2 GTP.

Involved in axoplasmic transport in neurons.

Dynein moves cargo from +–> - ends of the tubule (Retrograde)

Kinesin moves cargo in - –> + end. (Antegrade)

Question 6

Name 5 drugs that act on Microtubules.

Answer 6

Mebendazole - (antihelminthic) 
Griseofulvin - (antifungal) 
Colchicine (antigout) 
Vincristin/Vinblastine (anticancer) 
Paclitaxel (anticancer)

Question 7

Describe the structure of Cilia

Answer 7

9 microtubule doublets in the peripheral + 2 centrally.

Axonemal dynein is an ATPase that links peripheral doublets causing bending of cilium.

Question 8

What is Kartagener Syndrome.

Answer 8

Primary ciliary dyskinesia.

Immotile cilia due to defect in the dynein arm.
leads to male and female infertility due to imotile sperm and dysfunctional fallopian tubes.

Increased risk of ectopic pregnancy, Bronchiectasis, recurrent sinusitis, Situs inversus (Dextrocardia)

Question 9

Plasma membrane composition

Answer 9

Asymmetrical phospholipid bilayer.

Contains cholesterol, phospholipids, sphingolipids, glycolipids and proteins.

Fungal cell walls contain ergosterol (this is disrupted by Amphotericin B, itraconazole and miconazole etc)

Question 10

Describe the Sodium potassium ATPase pump.

Answer 10

transmembrane transporter of 3 Na out of the cell and 2 K into the cell.
When NA enters the pump, ATP binds on the cytosolic side which phosphorylates the complex causing a conformational change this opens the receptor to the outside of the cell, binds 2 K. the phosphate is removed and the 2 K are released to the inside of the cell.

3 Na enter –> ATP binds –> Na exit cell –> 2K bind –> dephosphorylation of pump –> 2 K released inside cell.

Question 11

Describe some inhibitors of the Na/K ATPase pump

Answer 11

Digoxin/Digitoxin bind to Na/K pump leading to increased intracellular calcium (prevents calcium leaving cell with Na) This leads to prolonged cardiac cycle and an increase in cardiac contractility.