6.1 Cell Cycle

Question 1

What is the cell cycle?

Answer 1

A highly ordered sequence of events occurring in a cell, resulting in the cell’s division and formation of 2 genetically identical daughter cells

Question 2

What are the 2 phases in the eukaryotic cell cycle?

Answer 2

Interphase and mitotic phase

Question 3

What is interphase?

Answer 3

The period of time when a cell is growing and functioning normally.
This is the majority of time a cell spends time in.

Question 4

Why is interphase an active process?

Answer 4

The cell is carrying out its normal functions, like producing hormones and enzymes

Question 5

In interphase, what happens to the cell’s DNA?

Answer 5

DNA is replicated and checked for errors in the nucleus

Question 6

In interphase, what happens in the cell’s cytoplasm?

Answer 6

Protein synthesis occurs

Question 7

In interphase, what happens to the mitochondria inside the cytoplasm?

Answer 7

Mitochondria grow and divide, increasing in number in the cytoplasm

Question 8

In interphase, what happens to chloroplasts in plant and algae cells?

Answer 8

Chloroplasts grow and divide, increasing in number in the cytoplasm

Question 9

In interphase, what happens to the cell’s metabolism?

Answer 9

Normal metabolic processes occur, e.g. respiration

Question 10

What are the 3 stages of interphase?

Answer 10

G1
S
G2

Question 11

What happens in G1 during interphase?

Answer 11

G1 - first growth phase: Proteins from which organelles form are produced, and organelles replicate. Cell size increases.

Question 12

What happens in S during interphase?

Answer 12

S - Synthesis Phase: DNA replicated in nucleus

Question 13

What happens in G2 during interphase?

Answer 13

G2 - second growth phase: Cell size increases, energy stores increase and duplicated DNA is checked for errors

Question 14

What are the 2 stages in the mitotic phase (cell division)?

Answer 14

Mitosis - Nucleus divides

Cytokinesis - Cytoplasm divides and two cells are produced

Question 15

What is the G0 phase?

Answer 15

When the cell leaves the cycle, temporarily or permanently.

Question 16

What are the 3 reasons for why a cell enters the G0 phase? (Not in spec)

Answer 16

Differentiation
DNA is damaged
Old cells

Question 17

Why is differentiation a reason for why a cell enters G0?

Not in spec

Answer 17

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

Question 18

Why is a cell’s DNA being damaged a reason for why a cell enters the G0 phase? (Not in spec)

Answer 18

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

Question 19

Why is a cell’s age a reason for why the cell enters G0?

Not in spec

Answer 19

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.

Question 20

What cell can re-enter the cell cycle after entering the G0 phase? (Not in spec)

Answer 20

Lymphocytes - can be stimulated tore-enter cell cycle and start dividing again

Question 21

What characteristics must a cell show to divide properly?

Answer 21

Cell must ONLY divide when:

• It’s the right size
• Replicated DNA is error-free
• Chromosomes are in correct position during mitosis

Question 22

1. What are checkpoints in the cell cycle?

2. What do they do?

Answer 22

1. 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

Question 23

What is the G1 checkpoint?

What does G1 check for?

Answer 23

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

Question 24

What is the G2 checkpoints?

What does it check for?

Answer 24

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

Question 25

What is the metaphase/spindle assembly checkpoint?

Answer 25

Part of mitosis where chromosomes are attached to spindles and have aligned.
Mitosis can’t occur until this checkpoint is passed.

Question 26

What are the 5 things that happen during interphase?

Answer 26

1. DNA replicated + checked for errors
2. Protein synthesis occurs in cytoplasm
3. Mitochondria grow and divide, their numbers increasing inside the cytoplasm
4. In plant and algal cell cytoplasm, chloroplasts grow + divide increasing in number
5. Normal metabolic cell processes occur