2.1 Cells Into Tissues

Question 1

Cells are held together in lateral domain in three ways. What is a tight junction? Give an example of where this is found. (3 points)

Answer 1

1) Fused plasmalemma
2) Forms a seal so only very selective permeability of molecules
3) Lining of the digestive tract

Question 2

Cells are held together in lateral domain in three ways. What is a desmosome? Give an example of where this is found.(4 points)

Answer 2

1) Interlocking intermediate filaments
2) Strengthens bond between cells
3) Resists against twisting and stretching
4) Tissues subject to stress e.g. Heart muscle

Question 3

Cells are held together in lateral domain in three ways. What is a gap junction? Give an example of where this is found.(4 points)

Answer 3

1) Connexons form channels
2) Allows cells to communicate with one another through movement of small ions
3) Allows coordination of actions
4) Cilia

Question 4

What is the basal domain?

Answer 4

Cells sit on an underlying layer called the basement membrane. It anchors the cells on top of it together, and anchors to the next layer below it.

Question 5

How do cells anchor to the basal domain? (2 ways)

Answer 5

1. Hemidesmosome

2. Focal Adhesions

Question 6

What protein used to anchor cells to the basement membrane in hemidesmosomes and focal adhesions?

Answer 6

Integrins

Question 7

What are integrins and their function?

Answer 7

1. Transmembrane proteins
2. Attach cell to ECM
3. Signal transduction
4. Allows movement of cells e.g. Epithelial to wound

Question 8

What enzyme used to get cells from a tissue?

Answer 8

Collagenase

Question 9

What is contact inhibition?

Answer 9

Once cells have made a mono layer by dividing, they stop dividing. Cancer prevention.

Question 10

What does senescence mean?

Answer 10

Progressive loss of function and then division and growth due to short telomere length

Question 11

How do cells communicate with each other? (6 points)

Answer 11

1. Direct - gap junctions
2. Autocrine - chemicals secreted bind to self-receptor
3. Paracrine - chemicals secreted bind to adjacent target cell
4. Endocrine - chemicals secreted enter blood and then target cell
5. Synaptic - electrical signal along nerve causes release of NT, diffusing across cleft to target cell
6. Neurocrine - electrical signal along nerve causes release of NT, enters blood and then target cell

Question 12

What kind of DNA is mtDNA?

Answer 12

Mitochondrial and circular

Question 13

Why and how does Necrosis occur?

Answer 13

Why - due to physical injury/stress

How - cell loses functional control, osmotic pressure leads to swelling, chromatin clumps and cell bursts.

Question 14

Why and how does Apoptosis occur?

Answer 14

Why - programmed cell death
How - bcl-2 on mitochondria inhibits this. But when it isn’t inhibited, catabolic processes mean enzymes digest components, cell shrinks etc. Cell fragments into small membrane bound apoptic bodies which are phagocytosed.

Question 15

Basic 4 types of tissue in the body?

Answer 15

1. Epithelial
2. Muscle
3. Nerve
4. CT

Question 16

Name the cells that do not have a surface and give an example

Answer 16

Epithelioid. Islets of langerhans in pancreas. Leydig cells in testes.

Question 17

Name extensions of the apical domain and give functions. (3 points)

Answer 17

1. Microvilli - cytoplasmic processes that increase surface area
2. Stereovilli - longer microvilli ltd to epididymis and sensory hair cells in ear
3. Cilia - motile cytoplasmic processes