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Cells and Control (Part 1) (Stem Cells (Differentiation (Stem cells can…
Cells and Control (Part 1)
Mitosis
Cell Cycle
Interphase
DNA spread out in a long spring
Cell has to grow and increase the subcellular structure such as mitochondria and ribosomes
Then duplicates so there is one copy of each new cell. DNA copies and forms into X shaped chromosomes
Mitosis and Cytokineses
Prophase
- Chromosomes condense, getting shorter and fatter. The membrane breaks down and nucleus breaks down and chromosomes lie free in cytoplasm
Metaphase
- Chromosomes line up at centere of the cell
Anaphase
- Cell fibres pull chromosomes apart and the two arms of each chromosome go to opposite sides of the cell
Telophase
- Membranes form around each cell and these become nuclei of two new cells - the nucleus has divided. Before it ends, cytoplasm and cell membrane divide to form separate cells and this is called
cytokineses
Used to grow and replace cells that have been damage. Also used for reproduction
Cell Differentiation and Growth
Growth
Growth is increase of size or mass
Cell Differentiation is the process where a cell changes to become a specialized cell so it can do a specific job. It allows the cell to work efficiently
Plants can grow by cell elongation and this is where a plant cell expands which makes the cell bigger
All growth in happens through cell division. When animals are young cells divide at a fast rate but when they are adults it is used for repair.
In plants growth in height is due to elongation, cell division happens at the tip of the roots and shoots.
Stem Cells
Differentiation
Stem cells can divide by mitosis to become new cells which then differentiate
Found in early human embryos, they have the potential to divide and produce any kind of cell at all. All different types of cell found in a human come from few cells in early embryo
Stem cells are important for growth and development of organisms
Adults also have stem cells but they are only found in certain places, like bone marrow. These are not versatile as embryonic cells and cannot produce any cell type.
Meristems
In plants, the only cells that divide by mitosis are the meristems
Meristem tissue is found in the areas of a plant that are growing
Meristems produce unspeicalised cells that are able to divide form any cell type and these cells can divide and differentiate an. ALso they generate any type of cell for as long as the plant lives
The unspecialised cells can go on to form specialised tissues like xylem and phloem
Stem cells in medicine
Doctors use adult stem cells to cure some diseases
It is possible to use stem cells to create specialised cells to replace those which have been damaged by disease or injury
Risks of stem cells in medicine
Tumour development - stem cells develop quickly and unable to control the rate at which the transplanted cells divide within a patient
Disease transmission - Viruses live inside cells. If donor stem cells are infected with a virus and it is not picked up, the virus could be picked up and passed on
Rejection - If transplanted cells are not grown using the patients own stem cells, the patients body may recognise the cells as a foreign and trigger immune response and get rid of them