cellb u18

Question 1

What is totipotency?

Answer 1

Ability of a fertilized egg to form an entire organism and all cell types; early cells can become any tissue.

Question 2

What do tissues require?

Answer 2

Mechanical strength, nutrient delivery, electrical signaling, and removal of dead/damaged cells (immune cells).

Question 3

What maintains tissue stability?

Answer 3

Cell communication, selective cell adhesion, and cell memory so cells stay in their correct identity.

Question 4

examples of tissue renewal rates?

Answer 4

Intestinal cells: 3–6 days; blood cells: 120 days; skin: ~2 months; nervous tissue: never divides.

Question 5

What are terminally differentiated cells?

Answer 5

Cells that cannot divide again (ex. red blood cells, upper skin cells, gut epithelium); must be replaced.

Question 6

What generates replacement cells for tissues?

Answer 6

Proliferating precursor cells derived from self-renewing stem cells.

Question 7

How are stem cells identified?

Answer 7

Through specific molecular markers; they are few, undifferentiated, and developmentally restricted.

Question 8

How is the small intestine renewed?

Answer 8

Stem cells in crypts → precursor cells → upward movement → differentiate into absorptive or secretory cells → die at villi tip.

Question 9

How is the epidermis renewed?

Answer 9

Stem and precursor cells sit on basal lamina → cells move outward → differentiate → dead cells shed at surface.

Question 10

10. What can one stem cell produce (example)?

Answer 10

Hematopoietic stem cells in bone marrow produce red blood cells, platelets, and a wide range of white blood cells.

Question 11

What controls stem cell proliferation in the intestine?

Answer 11

Wnt proteins promote stem/precursor cell proliferation in crypts; other crypt signals restrict Wnt activity to crypt regions.

Question 12

How do stem cells repair damaged tissues?

Answer 12

They proliferate indefinitely and replace lost cells. Example: bone marrow transplant replaces destroyed blood-forming cells (used for leukemia).

Question 13

What are embryonic stem (ES) cells?

Answer 13

Pluripotent cells that can differentiate into any cell type and integrate into tissues; used to study gene function and development.

Question 14

What are induced pluripotent stem (iPS) cells?

Answer 14

Adult cells reprogrammed by expressing Oct4, Sox2, and Klf4 → behave like ES cells (embryonic stem); potential therapies for muscle, nerve, beta cells, heart, etc.

Question 15

What are organoids and why are they important?

Answer 15

3D mini-organs formed from ES or iPS cells; resemble real organs; used to study development, genetics, cell interactions, and disease processes.