BL - Integrating Cells

Question 1

How long can packed red cells be stored at 6 degrees C for?

Answer 1

42 days

Question 2

What is found between adjacent epithelial cells?

Answer 2

Cell junctions

Question 3

What is the function of a cell junction?

Answer 3

They ensure that cells are tightly adhered to one another.

Question 4

What are the three types of cell junction?

Answer 4

Tight junctions, desmosomes and gap junctions

Question 5

How do tight junctions attach cells together?

Answer 5

They fuse the plasmalemma.

Question 6

What is the function of a tight junction?

Answer 6

They form an impenetrable barrier so molecules cannot pass between the two cells (and must pass through the cell instead). This allows them to act as a “security guard”.

Question 7

Give an example of where tight junctions can be found.

Answer 7

In the epithelial lining of the intestine.

Question 8

True or false - desmosomes are often found very close to tight junctions?

Answer 8

True

Question 9

Where are desmosomes often found?

Answer 9

Between epithelial cells that often undergo abrasion, eg in the skin.

Question 10

Which type of cell junction involves proteins that interlock between epithelial cells?

Answer 10

Desmosomes

Question 11

What is the function of a gap junction?

Answer 11

They allow cells to communicate with each other.

Question 12

What are connexons?

Answer 12

Small channels (proteins) that allows ions and small molecules to pass between cells so they can communicate.

Question 13

What is the basement membrane?

Answer 13

The structural site and point of attachment for overlying cells and underlying connective tissue.

Question 14

In what two ways can cells attach to the basement membrane?

Answer 14

Hemidesmosomes or focal adhesions

Question 15

What is the difference between a hemidesmosome and a desmosome?

Answer 15

Hemidesmosomes attach cells to the basement membrane, desmosomes attach cells to cells.

Question 16

What is the function of a focal adhesion?

Answer 16

They anchor intracellular actin filaments to the basement membrane, and aid cell movement.

Question 17

What are the two main functions of integrins?

Answer 17

Attachment of the cell to the extracellular matrix and signal transduction from the ECM to the cell.

Question 18

What is used to separate cells from tissues?

Answer 18

Collagenase or microdissection

Question 19

Give some disadvantages of cultured cells as a research tool.

Answer 19

They behave and look differently to cells in tissues, they demonstrate contact inhibition, they have a limited life span (“senescence”).

Question 20

In direct contact communication, which cells are contacted by the original cell?

Answer 20

The ones connected to it via connexons.

Question 21

In autocrine communication, which cells are contacted by the original cell?

Answer 21

The same cell (it is contacting itself).

Question 22

What is the difference between paracrine and endocrine communication?

Answer 22

Paracrine is to nearby cells via local regulator in the extracellular fluid while endocrine is to cells further away via hormone in the bloodstream.

Question 23

What is neurocrine communication?

Answer 23

Electrical signal moves along neuron, signal then travels through blood to the target cell. Eg anterior pituitary, posterior pituitary and adrenal medulla.

Question 24

What is the difference between necrosis and apoptosis?

Answer 24

Necrosis is unplanned and caused by physical disruption to the cell, while all cells are programmed for apoptosis.

Question 25

Explain how necrosis takes place.

Answer 25

1) The cell is damaged, eg. by bacteria
2) The cell loses functional control, osmotic pressure causes swelling in organelles
3) Chromatin clumps
4) Cell bursts
5) cytotoxic components spill out and cause tissue damage and inflammation

Question 26

What does the Bcl-2 protein on the outer mitochondrial membrane play a major role in?

Answer 26

Inhibiting apoptosis - if it is deactivated, apoptosis begins.

Question 27

How is the cell re-packaged for safe removal during apoptosis?

Answer 27

The chromatin condenses, the cell shrinks and it fragments into small apoptotic bodies.

Question 28

What happens to the compacted cell after it has split into apoptotic bodies?

Answer 28

It is phagocytised by adjoining cells.

Question 29

What’s the difference between endocytosis and exocytosis?

Answer 29

Endocytosis allows things to enter the cell, exocytosis allows things to exit the cell.

Question 30

Give some examples of cells that are static and do not require replacing.

Answer 30

Central nervous system, cardiac and skeletal muscle cells.

Question 31

Give some examples of stable cells that do not require frequent replacement.

Answer 31

Fibroblasts, endothelium, smooth muscle cells.

Question 32

Give some examples of cells that require constant replacing.

Answer 32

Blood, skin epithelium, gut epithelium.

Question 33

Most epithelial cells have a free surface and exhibit polarity. What are the three domains?

Answer 33

Apical, lateral and basal.

Question 34

Give an example of an epithelioid cell.

Answer 34

Leydig cells in testis, lutein cells of ovary, islets of langerhans in pancreas, parenchyma of adrenal gland.

Question 35

What’s the difference between microvilli, stereovilli and cilia?

Answer 35

Microvilli - cytoplasmic processes that extend from the cell surface.
Stereovilli - very long microvilli found in epididymis and sensory hair cells of ear
Cilia - cytoplasmic processes that can beat in synchrony (forward = effective, return = recovery).