Mod. 2 cell division (specialisation)

Question 1

stem cells

Answer 1

undifferenciated cells that originate from mitosis and meiosis. they have the potential to become any kind of specialised cell.

Question 2

How have erythrocytes specialised?

Answer 2

Flattened, biconcave shape increasing SA:V. They do not have nuclei, maximising space for haemoglobin.

Question 3

How have neutrophils specialised?

Answer 3

Multi-lobed nucleus, easier for getting into small spaces. Granular cytoplasm contains lysosomes, containing enzymes to attack pathogens.

Question 4

How have sperm cells specialised?

Answer 4

Long flagellum to propell the cell forwards. Lots of mitochondria because of the high metabolic rate.

Question 5

How have palisade cells specialised?

Answer 5

Contain lots of chloroplasts to absorb maximum light. Thin cells walls increasing rate of diffusion. large vacuole to maintain turgor pressure. Chloroplasts can move to absorb more light.

Question 6

How have root hair cells specialised?

Answer 6

Long extension into soil which increases SA:V. Vacuole contains sap lowering the water potential.

Question 7

How have guard cells specialised?

Answer 7

Open a gap depending on how much water they have. Low water, low pressure, gap opens, high water, high pressure, gap closed. thicker on one side so cell does not change shape symmetrically.

Question 8

What is the role of stem cells?

Answer 8

Stem cells repeatedly divide into both stem and specialised cells. Once the stem cell has become a specialised cell, it enters G0 stage, and cannot divide anymore.

Question 9

totipotent stem cell

Answer 9

stem cell that can differenciate into any kind of cell. e.g. fertilised egg/zygote.

Question 10

pluripotent stem cells

Answer 10

Can form tissue types but not whole organisms.

Question 11

multipotent stem cells

Answer 11

Can only form a limited range of cells, e.g. blood cells.

Question 12

What are the sources of stem cells in animals?

Answer 12

embryonic stem cells - stem cells from early embryonic development, are totipotent.
tissue stem cells - multipotent, found in specific tissues such as bone marrow. They can be triggered to become pluripotent.

Question 13

What are the sources of stem cells in plants?

Answer 13

meristematic tissue - wherever the growth is occurring. Also between phloem and xylem tissues.

Question 14

What are the uses of stem cells?

Answer 14

cure/treat many diseases, such as heart disease, type 1 diabetes, Parkinsons, Alzheimers, macular degeneration, birth defects.
cure injuries such as spinal, burns.
Used in drug trials and developmental biology.