Cell Biology

Question 1

What is the function of Type IV collagen and how is it made?

Answer 1

Forms a mesh and is a major component of the basal lamina.

Cannot form fibrils (pro-peptide is not cleaved like types I-III)

Question 2

How are collagen types I-III made?

Answer 2

Synthesized as pro-alpha chain molecule in ER. Modified in golgi and associate into a triple helix. Secreted from the cell. In extra cellular space, collagenase clip off pro-peptides allowing triple helix to associate into higher order structures forming fibrils and fibers

Question 3

What are the three components of an adhering junction?

Answer 3

Cadherins (transmembrane glycoprotein), Linker protein, and Actin microfilaments

Question 4

What do the adheren junctions link and what are two other names for them?

Answer 4

Cell-cell

Adhesion belt and zonula adheren

Question 5

What are the two types of Intermediate filament-based adhering junctions and what do they link?

Answer 5

Desmosomes: link cell-cell

Hemi-desmosomes: like cell to basal lamina of ECM

Question 6

What do tight junctions do and where are they found?

Answer 6

Create a permeability barrier, including maintaining polarity of the cell.
Found in epithelial sheets at the apical side of the cell.

Question 7

What are the proteins (two) that make up the tight junctions?

Answer 7

Claudin and Occludin

Question 8

What is the function of gap junctions and where are they found?

Answer 8

Facilitate communication between cells (including electrical activity)
Found in cardiac muscle

Question 9

What are the proteins called that make up a gap junction?

Answer 9

Connexin

Many connexins make up a connexon which links the two cells together

Question 10

What is elastin and where is it found in the body?

Answer 10

Connective tissue

Elastic component of skin, lungs, and blood vessels

Question 11

What is the sheath around elastin called and what is its function?

Answer 11

Fibrillin, a glycoprotein, keeps elastin from being too stretchy

Question 12

Bulky fillers are a component of cartilage and loose connective tissue. Proteoglycans are one specific example, what tissue type do they make up and what is their function within it?

Answer 12

Cartilage. Function is to attract H2O and act as hydrated gel to “absorb shock” within the tissue.

Question 13

When during the cell cycle do the three major checkpoints occur?

Answer 13

Transition from G1/S phase, G2/M phase, and from anaphase to metaphase during M phase.

Question 14

During which phase of mitosis does nuclear envelope breakdown occur?

Answer 14

Prometaphase

Question 15

What occurs before nuclear envelope breakdown occurs?

Answer 15

Condensing of chromosomes, mitotic spindle assembly/elongation between the two centrosomes

Question 16

What determines where the cytokinetic/contractile ring forms?

Answer 16

Signals from the metaphase plate. The cytokinetic ring forms perpendicular to the spindle, in the same plane as the metaphase plate.

Question 17

Which part of the cdk molecule is bound by phosphate to inhibit and activate the molecule?

Answer 17

Kinase subunit!