6.1 Flashcards
What is the cell cycle?
The cell cycle is a highly ordered sequence of events that take place in a cell, resulting in division of the cell, and the formation of two genetically identical daughter cells.
What are the 2 phases of the cell cycle?
Interphase
Mitotic phase
Describe the mitotic phase
Mitosis: the nucleus divides
Cytokinesis: the cytoplasm divides and two cells are produced.
Describe interphase
Period of growth and normal working between divisions.
The cell spends most of its time in interphase.
Refers to the resting phase as cells are not yet dividing.
Prepares cells for division while carrying out major functions.
Divided into 3 stages: G1,S,G2.
What happens during interphase? (6)
- DNA is replicated
- DNA is checked for errors in the nucleus.
- Protein synthesis occurs in the cytoplasm.
- Mitochondria grow and divide, increasing in number in the cytoplasm.
- Chloroplasts grow and divide in plant and algal cell.
- The normal metabolic processes of cells occur.
Explain G1
The first growth phase
Proteins from which organelles are synthesised are produced.
Organelles replicated.
The cell increases in size.
Explain the S phase
Synthesis phase
DNA is replicated in the nucleus.
Explain G2
Second growth phase
The cell continues to increase in size
Energy stores increase
Duplicated DNA is checked for errors.
What is G0?
G0 is the name given to the phase when the cell leaves the cycle,
Either temporarily or permanently.
There are a number of reasons for this.
A few types of cells that enter G0 can be stimulated to go back into the cell cycle and start dividing again, for example lymphocytes in an immune system
What are the reasons for G0?
Differentiation
DNA may become damaged
As you age
Explain differentiation
Cell that has become specialised to carry out a particular function is no longer able to divide.
It will carry out is function and will not enter the cell cycle again.
DNA of a cell may be damaged
The DNA is no longer viable.
A damaged cell can no longer divide.
Enters a period of permanent cell arrest (G0).
Cells can only divide a limited amount of times before they become senescent cells.
As you age
The number of cells in your body increases.
Growing numbers of senescent cells have be linked with many age related diseases, such as cancer and arthritis.
Why is it important to control the cell cycle?
Vital to ensure a cell only divides when it has grown to the right size.
The replicated DNA is error-free (or is repaired)
And the chromosomes are in their correct positions during mitosis.
Ensure daughter cells are genetically identical to parent cell.
Define checkpoints
Control mechanisms of the cell
Reduces changes of mutations
Ensures that two genetically identical daughter cells are created from the parent cell.
