2.8 Control of Cell division Flashcards
The divsion of cells can be described as
carefully coordinated
What is the alternating process or enlargment and cell division known as
cell cycle
the cells in our bodies that undergo rapid cell division are known as…
Stem cells (undifferentiated cells)
What are the key triggers for a stem cell to divide
size and singals from the envrionment (cell inhibtion, growth hormones)
What do external signals called grwoth factors (hormones) do
send messages for cells to divide
How are grwoth factors recieved
Receptor molecules in the plasma membrane. They pass this message on to relay proteins which move through the cytoplasm to the nucleus
What are the three main sections of interphase called
G1 (gap 1 or growth phase 1), S Phase (s = synthesis), G2 (Gap 2 or growth phase 2)
What occurs during G1
Accumultion of energy (ATP/glucose/oil)
During G1, the cell reaches checkpoint 1. What does this entail
The decsiion to divide - occurs when the cell is an appropirate size and has recieved an external signal to divide (growth factor)
What occurs during S Phase
DNA is replicated
What occurs during G2
cell reaches checkpoint 2 - makes sure DNA replication has occur properly
Presence of Mitosis Promoting Factor (MPF) starts mitosis
Why does mitosis begin
Due to an increase in MPF
Why does MPF levels rise
When CDK (enzyme) and Cyclin (substrate) combine to form MPF (creating an ezyme substrate complex
What occurs at checkpoint 3:
Checked to see if sister chromatids area correctly attached to spindle.
When does anaphase begin
When theres a drop in MPF
In cytokenisis, one daughter cell differentiates and becomings specialised in its function whilst the other…
remains a stem cell and goes through the cell cycle again
What are some extrenal factors that regulate the cell cycle
growth factors (hormones)
Physical signal contact inhibtion (cells need to have contact. When skin is cut and the cells on the edge of the gash will divide until they are touching other cells
Name some internal factors that regulate the cell cycle
MPF controls mitosis
Cyclin is a regulatory protein (levels rise and fall) which attaches to an enzyme (Cdk) (levels remain the same throughout the cycle to produce MPF(checkpoint 2)
A rise in MPF (due to a rise in cyclin initiates mitosis and a drop in MPF intiates anaphase (checkpoint 3)
Define cancer
Uncontrolled division of cells. Cancer cells produce daughter cells which both stay as stem cells and continue division or if orate
What are some things cancer has been linked to
Chemical carcinoens: casuing change in nucleotide sequence of the DNA (e.g. checmicals in tobacco smoke)
Radiation: Cause chromosome breaks (e.g. x-rays/UV light)
Viruses: Cause an addition of foreign DNA sequences in the host DNA
What is cell culturing
The ability to grow very small organisms in the labratory. This allows millions of cells to be grown in a small area, with hundreds of generations to be studied over a short time period.
What can the ability of cell culturing to study many generations over a short period of time allow
Mutations to be detected, isolated and studied
Culturing cells has occured over thousands of years including in foods such as»_space;>
bread, alcohol, cheese, yoghurt
What are the conditions required for cell culturing
An appropriate medium (agar or a broth)
Appropriate temp
Correct osmotic balance
Suitable pH
Oxygen (if aerobic)
Aseptic (free from any foreign bacteria)
