B Cell Specialisation and Stem Cells

Question 1

How are erythrocytes specialised for their function?

Answer 1

• They have a flattened, biconcave shape to increase SA:V ratio.
• Don’t contain nuclei to allow more space for haemoglobin.
• Flexible, allowing them to squeeze through narrow capillaries.

Question 2

How are neutrophils specialised for their function?

Answer 2

• Multi-lobed nucleus to make it easier to squeeze through small gaps to the site of infection.
• Contain many lysosomes containing lysozymes that digest and destroy pathogens.

Question 3

How are sperm cells specialised for their function?

Answer 3

• Flagellum allows them to swim towards the egg.
• Contain many mitochondria, which supplies energy for this movement.
• Acrosome containing digestive enzymes, allowing the sperm to penetrate the egg.

Question 4

How are squamous epithelial cells specialised for their function?

Answer 4

Cover organs and structures inside the body:
- flattened shape meaning substances diffuse over a short distance

Question 5

What is the role of epithelial cells?

Answer 5

• Protect body surfaces
• Aid diffusion and absorption

Question 6

How are ciliated epithelial cells specialised for their function?

Answer 6

Move substances across the respiratory system and female reproductive system:
- have cilia which beat in a rhythm to move mucus away from the lungs, and move the egg to the site of fertilisation

Question 7

How are root hair cells specialised for their function?

Answer 7

• Root hair increases surface area for absorption.
• Vacuole containing cell sap to maintain the concentration gradient between the cell and soil.
• Thin cellulose cell wall, so that substances diffuse over a short distance.

Question 8

How are palisade cells specialised for their function?

Answer 8

Specialised for photosynthesis:
- large number of chloroplasts to absorb light for photosynthesis
- thin cellulose cell wall to increase the rate of diffusion of carbon dioxide
- large vacuole to keep the leaf turgid and facing light

Question 9

How are guard cells specialised for their function?

Answer 9

Control the opening of the stomata:
- thick inner walls and thin outer walls allow the cell to bend when turgid, causing the stomata to open

Question 10

What is tissue?

Answer 10

• Specialised cells of the same type that are grouped together.
• Therefore a tissue is a group of cells that work together to perform the same function.

Question 11

Structure of squamous epithelium tissue

Answer 11

Made up of squamous epithelial cells

Question 12

Structure of ciliated epithelium tissue

Answer 12

Made up of ciliated epithelial cells and goblet cells (secrete mucus)

Question 13

Role of cartilage

Answer 13

A connective tissue that prevents bones rubbing together

Question 14

Role of muscle

Answer 14

Contracts in order to move bones

Question 15

Structure of xylem tissue

Answer 15

Made up of elongated dead cells that are strengthened by lignin

Question 16

Structure of phloem tissue

Answer 16

Made up of sieve tube elements separated by sieve plates

Question 17

What are organs?

Answer 17

• Groups of tissues that join together to carry out a particular function.
• Organs together form organ systems, such as the respiratory system.

Question 18

What are stem cells?

Answer 18

• Undifferentiated cells
• When they undergo mitosis they either form new stem cells, or differentiate into specialised cells.

Question 19

What is potency?

Answer 19

The ability of a stem cell to differentiate into a specialised cell:
1. Totipotent cells can differentiate into any cell (so can form whole organisms)
2. Pluripotent cells can differentiate into most cells
3. Multipotent cells can differentiate into a limited number of cells

Question 20

Where are multipotent cells found in humans?

Answer 20

• In the bone marrow
• These can differentiate into erythrocytes and neutrophils

Question 21

Where are totipotent cells found in humans?

Answer 21

In embryos

Question 22

Where are stem cells found in plants?

Answer 22

• In meristem (undifferentiated tissue)
• Meristem is found at the tips of shoots and roots, and in between the xylem and phloem

Question 23

Uses of stem cells

Answer 23

• Used in medicine: introduced into damaged tissue where they replace destroyed cells with healthy tissue, this can treat diseases such as Parkinson’s and Alzheimer’s.
• Used in research: drugs are tested on stem cells rather than people to see how effective the treatment is and whether there are any side effects.

Question 24

Issues with using stem cells

Answer 24

1. Ethical issues: collecting totipotent cells destroys embryos, creating ethical issues.
2. Harvesting bone marrow is difficult and painful for the donor, and there is a risk that the patents immune system will reject the donated cells.