Module 2 : Section 6 - Stem Cells and Differentiation

Question 1

Stem cells are …..

Answer 1

Unspecialised cells. They can develop into different types of cell

Question 2

What are multicellular organisms made of

Answer 2

• Made of many different cell types that are specialised for their function e.g. liver cells, muscle cells, white blood cells etc.
• all these specialised cell types originally came from stem cells
• all multicellular organisms have some form of stem cell

Question 3

Where are stem cells found in humans

Answer 3

Stem cells are found in early embryos and in a few places in adults. Stem cells in early embryos can develop into any type of human cell. Stem cells in adults can only develop into a limited range of cells

Question 4

Stem cells….

Answer 4

Divide to become new cells, which then become specialised

Question 5

What is differentiation

Answer 5

The process by which a cell becomes specialised for its job

Question 6

What are stem cells used for in animals

Answer 6

In animals, adult stem cells are used to replace damaged cells e.g. make new skin or blood cells

Question 7

What do plant use stem cells for

Answer 7

• plants are always growing, so stem cells are needed to make new shoots and roots throughout their lives
• stem cells in plants can differentiate into various plant tissue including xylem and phloem

Question 8

What can stem cells also divide into

Answer 8

Aside from specialised cell stem cells are able to divide to produce more undifferentiated stem cells e.g. they can renew themselves

Question 9

What do main bones in the body have in their centres

Answer 9

Marrow

Question 10

What do the marrows do

Answer 10

Here, adult stem cells divide and differentiate to replace worm out blood cells - erythrocytes (Red blood cells) and neutrophils (white blood cells)

Question 11

Where are stem cells found in plants

Answer 11

• Stem cells are found in the meristems (parts of the plant where growth can take place).
• in the root and stem, stem cells of the cells of the vascular cambium divide and differentiate to become xylem vessels and phloem sieve tubes

Question 12

Apart form differentiating into specialised cells and renewing themselves what may stem cells also be used for

Answer 12

Scientists think they could be used to replace damaged tissue in a range of diseases e.g. treating neurological disorders like Alzheimer’s or Parkinson’s

Question 13

How might stem cells help to treat Alzheimer’s

Answer 13

• with Alzheimer’s nerve cells in the brain die in increasing numbers
• this results in severe memory loss
• researchers are hoping to use stem cells to regrow healthy nerve cells in people with Alzheimer’s

Question 14

How might stem cells be used to treat Parkinson’s disease

Answer 14

• patients with Parkinson’s suffer from tremors that they can’t control
• the disease causes the loss of a particular type of nerve cell found in the brain
• these cells release a chemical called dopamine which is needed to control movement
• transplanted stem cells may help to regenerate the dopamine-producing cells

Question 15

How are neutrophils in animals specialised for their function

Answer 15

• their flexible shape allow them to engulf foreign particles or pathogens
• many lysosomes in their cytoplasm contain digestive enzymes to break down the engulfed particles

Question 16

How are erythrocytes in animals specialised for their function

Answer 16

• erythrocytes (red blood cells) carry oxygen in the blood
• biconcave disc shape provides large surface area for gas exchange
• no nucleus so more room haemoglobin the protein that carries oxygen

Question 17

How are epithelial cells in animals specialised for their function

Answer 17

• epithelial cells cover surfaces of organs
• the cells are joined by interlinking cell membranes and a membrane at their base
• ciliated epithelia (e.g. in the airways) have cilia that beat to move particles away
• squamous epithelia (e.g. in the lungs) are very thin to allow efficient diffusion of gases

Question 18

How are sperm cells in animals specialised for their functions

Answer 18

• Sperm cells (male sex cell) have flagellum so they swim to the egg (female sex cell)
• they have lots of mitochondria to provide the energy to swim
• the acrosome contains digestive enzymes to enable the sperm to penetrate the surface of the egg

Question 19

How are palisade mesophyll cells in plants specialised for their function

Answer 19

• Palisade mesophyll cells do most of the photosynthesis
• they contain many chloroplasts, so they absorb a lot of sunlight
• the walls are thin so carbon dioxide can easily diffuse into the cells

Question 20

How are root hair cells in plants specialised for their function

Answer 20

• root hair cells absorb water and mineral ions from the soil
• they have a large surface area for absorption
• thin permeable cell wall for entry of water and ions
• cytoplasm contains extra mitochondria to provide energy needed for active transport

Question 21

How are guard cells in plants specialised for their function

Answer 21

• guard cells are found in pairs, with a gap in between them to form a stoma
• this is one of the tiny pores in the surface of the leaf used for gas exchange
• in the light, guard cells take up water and become turgid
• their thin outer walls take and thickened inner walls force them to bend outwards opening the stomata, allows the leaf to exchange gases for photosynthesis