B2.3 Cell Specialisation

Question 1

Process of Fertilisation

Answer 1

1. Involves the fusion of male and female genetics to form a diploid zygote
2. Zygote will undergo cell division mitosis to create a clone of cells that is unspecialised
3. Cell differentiation must occur before Cell Specialisation, which happens because cells must undergo a change in gene expression in order to serve different functions

Question 2

2 Properties of Undifferentiated Cells

Answer 2

1. Retains the ability to divide -> Specialised cells are unable to undergo cell division
2. Retains the ability to specialise -> Potency

Question 3

2 Types of Stem Cells

Answer 3

1. Embryonic Stem Cells -> Any cells in between stage of fertilizations and 5-7 days after fertilizations
2. Adults Stem Cells -> Any cells inside the organism after 7 days since fertilizations

Question 4

Differences between Embryonic and Adult Stem Cells

Answer 4

1. Embryonic stem cells are found within the embryonic tissue whilst adult stem cells are found inside older embryo such as the brain, heart, and bone marrow
2. The function of embryonic stem cells is the generic development of an individual, whilst the function of adult stem cells are for replacing damaged tissue or remaining tissue
3. Embryonic stem cells are totipotent, which then becomes pluripotent, whilst adult stem cells are multipotent

Question 5

Advantages and Disadvantages of Embryonic and Adult Stem Cells Comparatively

Answer 5

E>A
- Embryonic Stem Cells can divide into more cell types
- Can lead to tissue formation during stem cell therapy because of slightly higher charge in comparison to adult stem cells

A>E
- Use of adult stem cells will not lead to death of early embryo
- Human can give consent to the use of adult stem cells
- Lower chance of rejection as Immune system will not recognise it as “non-self”

Question 6

Definition of Totipotent

Answer 6

Cells only found within very early stage embryo which can differentiate any cell type (including placenta) and grow into a new individual

Question 7

Definition of Pluripotent

Answer 7

Cells that can differentiate into most cell types except for placenta

Question 8

Definition of Multipotent

Answer 8

Cells for a specialised lineage of cells that give rise to tissue and organs

Question 9

Stem Cell Niche

Answer 9

Area of tissue that provides a specific environment where stem cells recieve stimuli to determine whether the stem cells stay undifferentiated or not

Question 10

Examples of stem cell niche

Answer 10

1. Bone Marrow inside bones contains stems cells in the region to give rise to new blood cells
2. Hair follicles contain cells for hair growth and hair follicle regeneration

Question 11

Constraints of cell size on SA:Vol Ratio

Answer 11

As cell size increases, surface area increases directly proportional to rate of diffusion, whilst volume increases directly proportional to the rate of metabolism. When cells increase, both factors increase but volume increases quicker, as if more reactions happen, more materials such as oxygen and glucose are needed. Surface area is not big enough to cope with material need. Hence, cell size is limiting to SA:V ratio