IB DP Biology Cell specialization Study Notes
IB DP Biology Cell specialization Study Notes
IB DP Biology Cell specialization Study Notes Study Notes at IITian Academy focus on specific topic and type of questions asked in actual exam. Study Notes focus on IB Biology syllabus with guiding questions of
- What are the roles of stem cells in multicellular organisms?
- How are differentiated cells adapted to their specialized functions?
Standard level and higher level: 4 hours
Additional higher level: 1 hour
B2.3.1—Production of unspecialized cells following fertilization and their development into specialized cells by differentiation
Differentiation: –
Cell differentiation is the WAY by which cells become specialized.
All cells of an organism contain all the chromosomes, hence the same genes
But all cells are specialized
e.g. White blood cells to fight against pathogens (1)
ex. Heart’s muscle cells to pump blood out of the heart (2)
ex. Skeletal muscles’ cells for body movement (3)
ex. Neurons carry nervous impulses (4)
- A cell does not need all proteins all the time
– A stomach cell needs the proteins the stomach needs
– An iris cell needs the proteins the iris needs
BUT
– A stomach cell does not need all proteins needed by the iris
– An iris cell does not need all proteins needed by the stomach
Gene : Fragment of chromosome containing instructions to produce a specific protein
An organism has different types of specialized cells because each cell type “expresses” ONLY the genes that are necessary for this cell type
In humans: A few hundred of genes among the 20 500 available genes are expressed in cells
All other genes are not expressed.
B2.3.2—Properties of stem cells
| POTENT | GIVE RISE TO | FOUND IN |
| Totipotent | Any cell type | Zygote to Morula |
Pluripotent “Embryonic | Any cell type | Inner mass cells of embryo |
| Multipotent | Several cell types | In some adult tissues |
| Unipotent | Only one cell type | In some adult tissues |
- Obtaining Embryonic stem cells 1/3
Fertility clinics: In Vitro Fertilization process for couples that cannot procreate naturally.
More embryos than needed for implantation are produced.
Source of embryonic stem cells
If allowed by laws
If agreed by donors
- Obtaining Embryonic stem cells 2/3
Genetic screening:
IVF produces numerous embryos
A single cell from 8-cell embryo is removed
This cell is used to check any genetic anomaly
e.g. Down syndrome, Cystic fibrosis…
The seven cells left are implanted into the mother’s uterus
Develop normally into blastocyst, fetus, and healthy baby
Could use the removed 8th cell to obtain/produce embryonic stem cells
Obtaining Embryonic stem cells 3/3
Blood of umbilical cord at birth
Contains embryonic stem cells
Can be collected and used
- Using embryonic stem cells in therapies
