Biochem - Cellular (Cytoskeleton, Plasma membrane, & their elements)

Question 1

What is the structure of a microtubule, and what are its components?

Answer 1

Cylindrical structure composed of a helical array of polymerized heterodimers of alpha- and beta-tubulin. Each dimer has 2 GTP bound

Question 2

What are 3 cellular structures into which microtubules are incorporated?

Answer 2

Incorporated into flagella, cilia, mitotic spindles.

Question 3

Briefly describe the growth and collapse of microtubules.

Answer 3

Grows slowly, collapses quickly

Question 4

What function do microtubules serve in neurons?

Answer 4

Also involved in slow axoplasmic transport in neurons

Question 5

Draw a microtuble, including and labeling the following: (1) Positive end (2) Protofilament (3) Negative end (4) Heterodimer.

Answer 5

See p. 78 in First Aid 2014 for visual at top left corner

Question 6

What is the function of Molecular motor proteins?

Answer 6

Molecular motor proteins - transport cellular cargo toward opposite ends of microtubule tracks

Question 7

What are 2 examples of Molecular motor proteins? What is the function of each?

Answer 7

(1) Dynein = retrograde to microtubule (+ => -) (2) Kinesin = anterograde to microtuble (- => +)

Question 8

Name 5 drugs that act on microtubules. Give the major clinical use or class of each.

Answer 8

Drugs that act on microtubules: (1) Mebendazole (anti-helminthic) (2) Griseofulvin (anti-fungal) (3) Colchicine (anti-gout) (4) Vincristine/Vinblastine (anti-cancer) (5) Paclitaxel (anti-cancer); Think: “Microtubules Get Constructed Very Poorly”

Question 9

What is the structure of cilia?

Answer 9

9 + 2 arrangement of microtubules

Question 10

What is Axonemal dynein, and what function does it serve?

Answer 10

Axonemal dynein - ATPase that links peripheral 9 doublets and causes bending of cilium by differential sliding of doublets

Question 11

What is another name for Kartagener syndrome? What is the defect, and what immediate effect does it have?

Answer 11

Kartagener syndrome (primary ciliary dyskniesia) - immotile cilia due to a dynein arm defect

Question 12

What symptoms are associated with Kartagener syndrome in males versus females, and why?

Answer 12

Results in male and female infertility due to immotile sperm and dysfunctional fallopian tube cilia, respectively

Question 13

For what condition does Kartagener syndrome increase the risk in women?

Answer 13

Increased risk of ectopic pregnancy

Question 14

What are 3 conditions that can be caused by Kartagener syndrome?

Answer 14

Can cause bronchiectasis, recurrent sinusitis, and situs inversus (e.g., dextrocardia on CXR)

Question 15

Name 3 different kinds/categories of cytoskeletal elements.

Answer 15

(1) Actin and myosin (2) Microtubule (3) Intermediate filament

Question 16

What are 4 processes/structures in which actin and myosin function?

Answer 16

Muscle contraction, Microvilli, Cytokinesis, Adherens junction

Question 17

Compare/Contrast actin and myosin, particularly in terms of their structure.

Answer 17

Actins are long, structural polymers. Myosins are dimeric, ATP-driven motor proteins that move along actins

Question 18

In one word, what is the major purpose of the microtubule?

Answer 18

Movement

Question 19

What are 5 structures/processes in which microtubules function?

Answer 19

Cilia, Flagella, Mitotic spindle, Axonal trafficking, Centrioles

Question 20

In one word, what is the major purpose of intermediate filaments?

Answer 20

Structure

Question 21

What are 6 examples of intermediate filaments?

Answer 21

(1) Vimentin (2) Desmin (3) Cytokeratin (4) Lamins (5) Glial fibrillary protein (GFAP) (6) Neurofilaments

Question 22

Describe the structure of the plasma membrane.

Answer 22

Asymmetric lipid bilayer

Question 23

What are 5 substances contained in the plasma membrane?

Answer 23

Contains cholesterol, phospholipids, sphingolipids, glycolipids, and proteins

Question 24

What substance do fungal membranes contain?

Answer 24

Fungal membranes contain ergosterol

Question 25

What cell type is identified using an immunohistochemical stain for Vimentin?

Answer 25

Connective tissue

Question 26

What cell type is identified using an immunohistochemical stain for Desmin?

Answer 26

Muscle; Think: “desMin = Muscle”

Question 27

What cell type is identified using an immunohistochemical stain for Cytokeratin?

Answer 27

Epithelial cells

Question 28

What cell type is identified using an immunohistochemical stain for GFAP?

Answer 28

Neuroglia; Think: “Gfap = neuroGlia”

Question 29

What cell type is identified using an immunohistochemical stain for Neurofilaments?

Answer 29

Neurons

Question 30

Where is the Na+-K+ ATPase located, and on which side is its ATP?

Answer 30

Na+-K+ ATPase is located in the plasma membrane with ATP site on the cytosolic side.

Question 31

What happens to Na+ and K+ for each ATP consumed by the Na+-K+ ATPase?

Answer 31

For each ATP consumed, 3 Na+ go out and 2 K+ come in

Question 32

What is the function of Ouabain?

Answer 32

Ouabain inhibits (sodium-potassium pump) by binding to K+ site

Question 33

Give 2 examples of cardiac glycosides. What are the mechanism and effects of cardiac glycosides?

Answer 33

Cardiac glycosides (digoxin and digitoxin) directly inhibit the Na+-K+ ATPase, which leads to indirect inhibition of Na+/Ca2+ exchange => increase [Ca2+]intracellular => increased cardiac contractility