b2.3 cell specialisation

Question 1

What is a zygote?

Answer 1

A single, unspecialized cell formed from fertilization.

Question 2

How do chemical gradients impact gene expression in an embryo?

Answer 2

Chemical gradients activate or silence genes, guiding differentiation into specialized cells.

Question 2

What is a stem cell niche?

Answer 2

A microenvironment that regulates stem cell activity and maintains their function.

Question 2

What are two key properties of stem cells?

Answer 2

1. Self-renewal – They can divide indefinitely.
2. Potency – They can differentiate into various cell types

Question 3

Where are two types of multipotent stem cells found in adults, and what are their functions?

Answer 3

• Hematopoietic stem cells (bone marrow) – Form blood cells.
• Mesenchymal stem cells (bone marrow, fat) – Produce bone, cartilage, and fat cells.

Question 4

What are totipotent, pluripotent, and multipotent stem cells?

Answer 4

• Totipotent – Can form any cell plus extra-embryonic tissue (e.g., fertilized egg).
• Pluripotent – Can form any body cell (e.g., embryonic stem cells).
• Multipotent – Can form a limited range of cells (e.g., adult stem cells).

Question 5

Why are pluripotent stem cells most prevalent in early embryonic development?

Answer 5

Because they give rise to all tissues needed for a developing organism.

Question 6

How does cell size relate to specialized functions in different cell types?

Answer 6

• Sperm – Small, streamlined for motility.
• Egg – Large, stores nutrients for early development.
• Red blood cells – Small, flexible for oxygen transport.
• White blood cells – Larger, attack pathogens.
• Neurons – Long, transmit signals.
• Striated muscle fibers – Large, allow contraction.

Question 7

What is the relationship between cell size and SA:V ratio?

Answer 7

• Smaller cells → Higher SA:V ratio → Efficient transport.
• Larger cells → Lower SA:V ratio → Slower exchange of nutrients/waste.

Question 7

How do you calculate the surface area, volume, and SA:V ratio of a cube?

Answer 7

• Surface area = 6 × (side length²)
• Volume = (side length³)
• SA:V ratio = Surface area ÷ Volume

Question 7

What activities occur in a cell’s volume and on its surface?

Answer 7

• Volume – Metabolic reactions (energy use, molecule synthesis).
• Surface – Exchange of substances (nutrient intake, waste removal).

Question 8

What are the benefits and limitations of using cubes to model a cell’s SA:V ratio?

Answer 8

• Benefit: Simple calculations to visualize SA:V changes.
• Limitation: Real cells are irregularly shaped, affecting actual exchange efficiency.

Question 9

Why are cells often limited in size by their SA:V ratio?

Answer 9

If a cell grows too large, its surface can’t exchange materials fast enough to meet metabolic needs.