chapter 2.8 control of cell division Flashcards
Cell division may be regulated by internal and external factors. The cell produces gene products that regulate the cell cycle. Describe the stages in the cell cycle (including checkpoints). Explain that hormones may regulate cell division. Carcinogens upset the normal controls of cell division by causing mutations. Human beings culture cells for a variety of purposes. Describe techniques of cell culture, and discuss the applications and limitations of contemporary examples of their use.
Define the cell cycle?
The cell cycle is a series of events that takes place in a cell as it grows and divide.
remembering the rate of cell division is not identical for all cells, for insance red blood cells and skin cells are made quickly whilst mature nerve cells do not divide
What are the three stages of cell cycle?
- mitosis: division of the nucleus
- cytokinesis: division of the cytoplas and the formation of two new cells
- interphase: time in between cell divisions(includes biochemical proccesses such as transcription,translation and DNA replication)
How have the stages been summarised into events of the cell cycle?
- G0: cells are removed from the cycle and are not dividing though functioning
- G1: cell growth, ribosome synthesis, protein synthesis
- S: DNA replication, histone synthesis, phospholipid synthesis
- G2: developing and preparing organelles for division
- M: mitosis: division of the nucleus
- Cytokinesis: division of the cytoplasm and the cell divides.
What are cell checkpoints?
A control point in the cycle where a cell
‘checks’ certain conditions
A decision is then made to determine
whether the cell cycle continues or not
Name the three cell checkpoints?
At the end of G1 there is a checkpoint in
which cell growth is assessed
At the end of G2 there is a checkpoint
where the progress of DNA replication is
assessed before the cell proceeds into
mitosis
The progress of mitosis is checked at the
third checkpoint called M during
metaphase
if the expectations are not met at each point they will be declared programmed cell death
What internal factors control the regulation of cell cycle
- Cyclin Dependent Kinases (CDKs) –
enzymes - Cyclin – protein
Are both two important proteins in regulating cell cycle. Cyclin binds to the active site of CDKs to form the complex molecule called mitosis promoting factor (MPF) which stimultes the cell to divide.
*Cyclin Dependent Kinases (CDKs) are enzymes that remain at a stable concentration throughout the cell cycle and are only transcribed aroung the G2 phase. CDK can be reused through, where its degraded after use and binds to cyclin again. *
What external factors control the regulation of the cell cycle?
Nutrient dependence: certain nutrients need to be present in the extracellular fluid in order for the cell to divide.
Anchorage dependence: some cells need to be attached to a substrate in order to divide
Density dependence: excess contact with other cells, also called contact inhibition (no room for more cells to be made)
These all affect the production of MPF
What chemical trigger control the regulation of the cell cycle?
Primarily includes hormones e.g. growth hormones, sex hormones and cytokinesis in plants.
These hormones often stimulate cells to release molecules called growth factors. If cells are deprived from growth factors they generally will not divide.
How do carcinogens impact the regulation of the cell cycle?
Carcinogens are chemical mutagens which can increase the rate of mutations in oncogenes. Examples of carcinogens can include asbestos
fibres, tobacco and radiation.
Oncogenes are genes that produce proteins
involved in the regulation of cell division (genes
for cyclins and CDKs).Mutations in these genes can interfere with signals at the checkpoints
What can mutations in oncogenes lead to?
Cancer (uncontrolled cell growth)
Begins with one abnormal cancer cell which
divides to form a tumour.
How can the cell cycle/celldivision be controlled through cell culture?
Growing cells in the laboratory
Cells are grown in a petri dish containing the
nutrient agar (providing the nutrients cells need to divide).
The environment for culturing cells must be
sterile contain nutrients and hormones, and
have the correct pH and temperature.
How is cell culture applied/ used throughout science?
- Cloning for protein production – i.e. insulin
- Cloning whole organisms – dolly the sheep
- Culturing skin cells for grafting
- Vaccine production
- Testing pharmaceutical products
