B2.3 Specialization

Question 1

What is fertilization, and what happens immediately following it?

Answer 1

Fertilization is the process where a sperm cell fuses with an egg cell to form a zygote. Immediately following fertilization, the zygote begins to divide and develop into an embryo.

Question 2

What are unspecialized cells, and what is their role in development?

Answer 2

Unspecialized cells, or stem cells, have the ability to become different types of specialized cells. They play a key role in growth and tissue repair.

Question 3

Collections of similar cells are called tissues. How many different distinct highly specialized cell types have been recognized in humans?

Answer 3

There are over 200 distinct, highly specialized cell types in humans.

Question 4

How do cells become specialized during differentiation?

Answer 4

During differentiation, cells receive signals that turn certain genes on or off, leading them to develop specific structures and functions.

Question 5

Describe what is meant by the term stem cell.

Answer 5

A stem cell is an unspecialized cell capable of dividing and developing into various specialized cell types.

Question 6

When a stem cell receives a signal, it begins to differentiate. What does that mean?

Answer 6

Differentiation is the process by which a stem cell becomes specialized, taking on a specific function in the body.

Question 7

Why would using a patient’s own stem cells to grow new tissue be better than using donor cells?

Answer 7

Using a patient’s own stem cells reduces the risk of immune rejection and complications compared to using donor cells.

Question 8

What is a stem cell niche, and why is it important in adult humans?

Answer 8

A stem cell niche is a specific microenvironment that supports and regulates stem cells. It is important for maintaining stem cell function and tissue regeneration.

Question 9

Define the following types of stem cells: Totipotent, Pluripotent, Multipotent, Unipotent.

Answer 9

Totipotent: Can become any cell type, including placental cells (e.g., zygote).
Pluripotent: Can become any cell type in the body but not placental cells (e.g., embryonic stem cells).
Multipotent: Can become a limited range of cells (e.g., adult stem cells in bone marrow).
Unipotent: Can only become one cell type (e.g., muscle stem cells).

Question 10

Why do cells vary in size within the human body?

Answer 10

Cell size varies to suit specific functions; for example, nerve cells are large for long-distance signaling, while red blood cells are small to move through capillaries easily.

Question 11

How does the size of cells relate to their specialization and function in the body? Provide an explanation and comparison for the following:
a. Gametes (male and female)
b. Red blood cells/white blood cells
c. Striated muscle fibers

Answer 11

Gametes: Small size helps in fertilization; sperm cells are streamlined for mobility, and egg cells are large to store nutrients.
Red/White Blood Cells: Small to travel through blood vessels and reach tissues quickly; white blood cells can change shape to combat pathogens.
Striated Muscle Fibers: Long and thin, allowing for effective contraction and movement.

Question 12

Describe four adaptations of sperm cells that make them specialized for their function.

Answer 12

Sperm cells have a tail for movement, many mitochondria for energy, a streamlined shape, and enzymes to penetrate the egg.

Question 13

Compare and contrast totipotent, pluripotent, and multipotent stem cells in terms of their developmental stage and differentiation potential.

Answer 13

Totipotent: Found in early embryonic stages; can develop into any cell type, including placental cells.
Pluripotent: Found slightly later in the embryo; can develop into nearly any cell type but not placental cells.
Multipotent: Found in adult tissues; can only differentiate into cell types within a specific family, such as blood or bone cells.

Question 14

Why do cells vary in size within the human body?

Answer 14

Cell sizes vary to suit different functions; some cells need to be small for quick nutrient exchange, while others need to be larger to perform complex tasks or store more information.

Question 15

What would be the consequences for a cell if the cell membrane was not large enough to have adequate channels for bringing in nutrients and removing waste?

Answer 15

The cell would be unable to efficiently exchange materials, leading to a buildup of waste and a shortage of nutrients, which could result in cell death.

Question 16

Suggest cell shapes that would balance function and materials movement for each of the following:
a. Long-distance communication
b. Stretching
c. Storage
d. Covering and protecting
e. Importing large quantities of material for transfer to other cells

Answer 16

Long-distance communication: Long and thin (e.g., neuron shape).
Stretching: Flexible and elongated (e.g., muscle fibers).
Storage: Spherical or cube-shaped to hold more (e.g., fat cells).
Covering and protecting: Flat and broad (e.g., epithelial cells).
Importing large quantities of material: Folded or with many channels (e.g., intestinal cells).

Question 17

Which size of cube-shaped cells would be most efficient in removing waste by diffusion?

Answer 17

The smallest cube-shaped cell, as it has the highest surface area-to-volume ratio, allowing more efficient waste removal.

Question 18

What mechanisms other than cell division do cells use to maintain viable, efficient SA
ratios?

Answer 18

Cells form microvilli to increase surface area or become flattened to increase SA
without increasing volume.

Question 19

How do multicellular organisms maintain efficient SA
ratios?

Answer 19

They develop organ systems with specialized structures like villi or alveoli to facilitate efficient material exchange.

Question 20

How does the invasive Caulerpa algae genus break the rules of SA?

Answer 20

Caulerpa algae grow as single-celled, large organisms, using their unique structure to overcome typical SA
limitations by extending and branching in marine environments.

Question 21

Muscle cells have more than __________ __________ per cell

Answer 21

One Nucleus

Question 22

Muscle cells called fibers can be very long (_______mm)

Answer 22

300 mm

Question 23

Skeletal muscle fibers are surrounded by a _________ plasma membrane but are ________-nucleated

Answer 23

Single, multi-nucleated

Question 24

Explain the adaptations of cardiac muscle cells that make them specialized for their function.

Answer 24

Cardiac muscle cells are branched to allow for efficient and coordinated contractions, are rich in mitochondria for energy, and have intercalated disks for rapid signal transmission.

Question 25

Contrast the branching of cardiac muscle cells with the unbranched nature of striated muscle fibers.

Answer 25

Cardiac muscle cells branch, enabling coordinated contractions, while striated muscle fibers are long and unbranched, suitable for continuous, controlled movements.

Question 26

Explain four adaptations of sperm cells in humans that make them highly specialized for their function.

Answer 26

Sperm cells have a tail for movement, a streamlined shape, many mitochondria for energy, and an acrosome containing enzymes to penetrate the egg.

Question 27

Explain four adaptations of egg cells (ova) in humans that make them specialized for fertilization.

Answer 27

Egg cells are large to store nutrients, have a protective outer layer, contain genetic material, and have signaling molecules to attract sperm for fertilization.

Question 28

What are Type 1 and Type 2 pneumocytes, and what is their primary function in the alveoli?

Answer 28

Type 1 pneumocytes are flat, thin cells that line the alveolar surface and facilitate gas exchange. Type 2 pneumocytes are cubic-shaped cells that secrete surfactant to reduce surface tension and can convert to Type 1 cells to repair the alveolar surface after injury.

Question 29

How do Type 1 and Type 2 pneumocytes differ in shape, size, and organelle distribution?

Answer 29

Type 1 cells are larger, flat, and thin with sparse organelles, while Type 2 cells are smaller, cubic, and densely populated with organelles.

Question 30

Describe the nuclei of Type 1 and Type 2 pneumocytes and their occurrence in the alveoli.

Answer 30

Type 1 cells have small nuclei and are less frequent, covering nearly 95% of the alveolar surface. Type 2 cells have large nuclei, are more frequent (1:2 ratio with Type 1), but contribute less to alveolar lining.

Question 31

What structures or features distinguish Type 1 and Type 2 pneumocytes in terms of surface area coverage and secretory granules?

Answer 31

Type 1 pneumocytes cover most of the alveolar surface and lack secretory granules. Type 2 pneumocytes have lamellar bodies (secretory granules for surfactant) but cover a smaller surface area.

Question 32

How are Type 1 and Type 2 pneumocytes connected in the alveoli?

Answer 32

Type 1 pneumocytes are linked by tight junctions to prevent fluid leakage, whereas Type 2 pneumocytes lack specific cell junctions.

Question 33

What are alveoli, and what is its function in the respiratory system?

Answer 33

The alveoli are tiny air sacs in the lungs where gas exchange occurs. Oxygen enters the blood, and carbon dioxide is removed through the alveolar walls, which are thin and surrounded by capillaries to maximize the efficiency of gas exchange.

Question 34

Where are bone marrow and hair follicle stem cells located?

Answer 34

Bone marrow is located in cavities of bones (e.g., femur, pelvis), while hair follicle stem cells are found at the base of hair follicles (hair bulge).

Question 35

What types of stem cells are found in bone marrow and hair follicles?

Answer 35

Bone marrow contains Hematopoietic Stem Cells (HSCs), and hair follicles contain Hair Follicle Stem Cells (HFSCs).

Question 36

What are the niche components for bone marrow and hair follicle stem cells?

Answer 36

Bone marrow niche components include stromal cells and extracellular matrix, while hair follicle niche components include the dermal papilla and surrounding epithelial cells.

Question 37

What is the function of the stem cell niches in bone marrow and hair follicles?

Answer 37

Bone marrow niches maintain HSCs and regulate blood cell production, while hair follicle niches maintain HFSCs and regulate hair growth cycles.

Question 38

What signaling factors influence bone marrow and hair follicle stem cells?

Answer 38

Bone marrow is influenced by cytokines and growth factors, while hair follicles are influenced by BMP, Wnt, and Notch signaling pathways.

Question 39

How do bone marrow and hair follicles contribute to cell proliferation?

Answer 39

Bone marrow promotes the proliferation and differentiation of blood cells, while hair follicles activate HFSCs during hair regeneration.

Question 40

What role do bone marrow and hair follicles play in cell differentiation?

Answer 40

Bone marrow guides differentiation into various blood cells, while hair follicles induce differentiation into hair cell components.

Question 41

Describe the regeneration capacity of bone marrow and hair follicles.

Answer 41

Bone marrow ensures a constant supply of blood cells, while hair follicles support cyclic hair regeneration.

Question 42

How do bone marrow and hair follicles respond to tissue damage?

Answer 42

Bone marrow increases cell division for rapid repair, and hair follicles activate HFSCs to regenerate damaged hair.

Question 43

What is the importance of bone marrow and hair follicles in regenerative medicine?

Answer 43

Bone marrow serves as a source of donor cells for transplants, while hair follicles hold potential for hair regrowth treatments.