6.1 Cell Cycle Flashcards
What is the cell cycle?
A highly ordered sequence of events occurring in a cell, resulting in the cell’s division and formation of 2 genetically identical daughter cells
What are the 2 phases in the eukaryotic cell cycle?
Interphase and mitotic phase
What is interphase?
The period of time when a cell is growing and functioning normally.
This is the majority of time a cell spends time in.
Why is interphase an active process?
The cell is carrying out its normal functions, like producing hormones and enzymes
In interphase, what happens to the cell’s DNA?
DNA is replicated and checked for errors in the nucleus
In interphase, what happens in the cell’s cytoplasm?
Protein synthesis occurs
In interphase, what happens to the mitochondria inside the cytoplasm?
Mitochondria grow and divide, increasing in number in the cytoplasm
In interphase, what happens to chloroplasts in plant and algae cells?
Chloroplasts grow and divide, increasing in number in the cytoplasm
In interphase, what happens to the cell’s metabolism?
Normal metabolic processes occur, e.g. respiration
What are the 3 stages of interphase?
G1
S
G2
What happens in G1 during interphase?
G1 - first growth phase: Proteins from which organelles form are produced, and organelles replicate. Cell size increases.
What happens in S during interphase?
S - Synthesis Phase: DNA replicated in nucleus
What happens in G2 during interphase?
G2 - second growth phase: Cell size increases, energy stores increase and duplicated DNA is checked for errors
What are the 2 stages in the mitotic phase (cell division)?
Mitosis - Nucleus divides
Cytokinesis - Cytoplasm divides and two cells are produced
What is the G0 phase?
When the cell leaves the cycle, temporarily or permanently.
What are the 3 reasons for why a cell enters the G0 phase? (Not in spec)
Differentiation
DNA is damaged
Old cells
Why is differentiation a reason for why a cell enters G0?
Not in spec
Cells that become specialised are no longer able to divide.
A specialised cell will carry out its function indefinitely and will never re-enter the cell cycle
Why is a cell’s DNA being damaged a reason for why a cell enters the G0 phase? (Not in spec)
A damaged cell can’t divide and enters a period of permanent cell arrest, G0
Most cells divide a limited number of times and then become senescent
Why is a cell’s age a reason for why the cell enters G0?
Not in spec
As you age, the amount of cells in your body increases.
Growing amount of senescent cells have been linked with age-related diseases, such as cancer and arthritis.
What cell can re-enter the cell cycle after entering the G0 phase? (Not in spec)
Lymphocytes - can be stimulated tore-enter cell cycle and start dividing again
What characteristics must a cell show to divide properly?
Cell must ONLY divide when:
- It’s the right size
- Replicated DNA is error-free
- Chromosomes are in correct position during mitosis
- What are checkpoints in the cell cycle?
2. What do they do?
- Control mechanisms of the cell cycle.
2. Monitor whether processes at each phase of cell cycle have been accurately completed before entering the next phase
What is the G1 checkpoint?
What does G1 check for?
Occurs at the end of G1, before entry into S phase. If the cell meets the G1 requirements, its DNA starts to replicate. If not, it enters G0.
Checks for: Cell size Nutrients Growth factors DNA damage
What is the G2 checkpoints?
What does it check for?
At end of G2 phase, before start of mitotic phase.
Checks for:
Cell size
DNA replication
DNA damage
If cell meets G2 requirements, cell begins mitosis
What is the metaphase/spindle assembly checkpoint?
Part of mitosis where chromosomes are attached to spindles and have aligned.
Mitosis can’t occur until this checkpoint is passed.
What are the 5 things that happen during interphase?
- DNA replicated + checked for errors
- Protein synthesis occurs in cytoplasm
- Mitochondria grow and divide, their numbers increasing inside the cytoplasm
- In plant and algal cell cytoplasm, chloroplasts grow + divide increasing in number
- Normal metabolic cell processes occur
