Cell surface specialization

Question 1

Cytoskeleton

Answer 1

• Plays a role in cell shape and facilitating movement
• Important for the formation of the specialized features on surface structures
  Ex. protrusions that increase the cell Surface area, and therefore increase the diffusion rate

Question 2

Microtubules

Answer 2

• Tubulin-based filaments; cylindrical hollow tubes.
• Involved in cell division, intracellular transport, and cell shape maintenance

Question 3

Microtubules role in transport

Answer 3

Form roads that originate from centrosomes (2 centrioles). Motor proteins walk along and carry intracellular cargo along the roads.

Question 4

Formation of microtubules

Answer 4

Built when tubulin dimers (most basic component) polymerizes into protofilament. Multiple protofilaments combine together in a circle (creating a space called a lumen) to form the microtubule

Question 5

Microtubules remodelling

Answer 5

Dynamic instability

Microtubules can grow and shrink; regulated by many factors.
Can be targeted by drugs to treat certain inflammatory conditions and cancer

Question 6

Microtubules role in cilia and flagella

Answer 6

Microtubules form the core of cilia and flagella.

Involved in cellular movement and transport of extracellular materials

Beat together in one power stroke

Question 7

Microtubules role in cell division

Answer 7

Centrioles migrate to poles of the cell and while this happens, they build Microtubules or in this case the mitotic spindles. These spindles attach to the chromosomes for division… dysfunction can lead to genetic abnormalities

Question 8

Microfilaments

Answer 8

Actin-based filaments; 2 helically- intertwined strands of actin

Involved in cell movement, muscle contraction, and cell shape changes

Question 9

Growth of microfilaments

Answer 9

Treadmilling

1. Actin polymerization at leading edge creating a protrusion
2. Cell adhesion at leading edge. A glycoprotein binds to extracellular matrix protein anchoring the cell
3. Actomyosin contraction- myosin motors generate force by sliding along actin filaments causing contraction at rear edge of cell
4. Rear end retraction- the actin filaments disassemble, and the cells rear end retracts allowing the cell to move forward

Question 10

microvilli

Answer 10

actin filaments

provide cell shape and flexibility
increase surface area

Question 11

intermediate filaments

Answer 11

• Made of proteins
• provide mechanical strength and helps maintain cell integrity

Question 12

polarity in epithelial cells

Answer 12

• Apical surface- faces free space (lumen)
• Basal surface- faces connective tissues
• Lateral surface- between cells

Question 13

Cell junctions between epithelia

Answer 13

Tight junction- forms barrier between neighbouring cells
- Often near apical surface

Adherens junction- joins actin bundle of one cell to an actin bundle on another cell - Mechanical strength

Desmosome- joins the intermediate filaments in one cell to those in a neighbour
- Mechanical strength

Gap junction- forms channels allowing for communication between cells

Hemidesmosome- anchors intermediate filaments in a cell to the basal lamina
- Mechanical strength