1. The Cell Cycle & Mitosis
Chapter 5

2. 5.1 – The Cell Cycle Key Concept:
Cells have distinct phases of growth, reproduction, and normal functions.

3. When a living thing grows, what happens to its cells?
Does an animal get larger because each cell increases in size or because it produces more of them?
What are some things that all cells in your body must have?

5. The cell cycle has 4 main stages.
The cell cycle is a regular pattern of growth, DNA replication, and cell division.

6. The main stages of the cell cycle are: Gap 1, Synthesis, Gap 2, & Mitosis.
Gap 1 (G1): cell growth and normal functions, copy organelles (most cells spend most of their time here)
Only proceed to S if the cell has enough nutrition, adequate size, undamaged DNA
Synthesis (S): copies DNA
Gap 2 (G2): additional growth
Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)
Mitosis occurs only if the cell is large enough and the DNA undamaged.

8. Cells divide at different rates.
The rate of cell division varies with the need for that type of cell.
Some cells are unlikely to divide
Example: neurons – stay in G0

9. Cell size is limited. Cell volume increases faster than surface area.
Cells need to stay small to allow diffusion and osmosis to work efficiently.

10. Surface area must allow for adequate exchange of materials.
Cells that must be large have unique shapes (i.e. neurons)

11. 5.2 – Mitosis & Cytokinesis
Key Concept:
Cells divide during mitosis and cytokinesis into two new daughter cells.

12. Chromosomes condense at the start of mitosis.
Chromosomes: carry genetic information (DNA) that is passed from one generation of cells to the next.
DNA wraps around proteins (histones) that condense it.

13. Chromatin: DNA plus proteins (histones) is called chromatin.
Chromatid: Each duplicated chromosome is composed of two chromatids
Centromere: Sister chromatids are held together at the centromere.
Telomeres: protect DNA and do not include genes (like the caps on shoelaces)

15. Mitosis and cytokinesis produce two genetically identical daughter cells.
Interphase prepares the cell to divide.
DNA is duplicated.
Includes G1, S, G2

17. Mitosis divides the cell’s nucleus in four phases - PMAT
Prophase – first & longest
Chromosomes condense, spindle fibers form, and the nuclear membrane disappears.

18. Mitosis divides the cell’s nucleus in four phases.
Metaphase
Chromosomes line up across the middle of the cell.

19. Mitosis divides the cell’s nucleus in four phases.
Anaphase
Sister chromatids are pulled apart to opposite sides of the cell.

20. Mitosis divides the cell’s nucleus in four phases.
Telophase
Two nuclei form at opposite ends of the cell, the nuclear membranes reform, and the chromosomes uncoil back into chromatin

21. Cytokinesis differs in animal and plant cells.
Cytokinesis is when the cytoplasm separates
Animal cells: membrane pinches the
two new cells apart
Plant cells: a cell plate (new cell wall) separates the two new cells

22. Mitosis in a Plant Cell

25. 5.3 – Regulation of the Cell Cycle
Key Concept:
Cell cycle regulation is necessary for healthy growth.

26. Internal and external factors regulate cell division.
External Factors: come from outside cell
Internal Factors: come from inside cell
Include physical and chemical signals
Cell to cell contact, Growth factors
Trigger internal factors, which affect the cell cycle
Help to advance a cell to different parts of the cell cycle

27. What happens when the cell cycle isn’t regulated properly?

28. Cell division is uncontrolled in cancer.
Cancer cells form disorganized clumps called tumors.
Benign tumors remain clustered and can be removed.
Malignant tumors metastasize, or break away, and can form more tumors.

29. Apoptosis is programmed cell death.
Apoptosis is the process of programmed cell death.
Normal feature in healthy organisms
Caused by a cell’s production of self-destructive enzymes
Example of apoptosis in healthy organisms: Occurs during fetal development (responsible for
separation of fingers and toes)

30. Cancer can also be caused by genetics (i.e. BRCA1)
Cancer cells do not carry out normal cell functions (this is part of why they’re so bad!)
Cancer cells come from normal cells with damage to genes involved in cell-cycle regulation.
Carcinogens are substances known to cause cancer (they damage those genes)
Chemicals, tobacco smoke, X-rays, UV rays, HPV
Cancer can also be caused by genetics (i.e. BRCA1)
Standard cancer treatments typically kill both cancerous and normal, healthy cells.

31. 5.4 – Asexual Reproduction
Key Concept:
Many organisms reproduce by cell division.

32. Binary fission is similar to mitosis.
Asexual reproduction is the creation of offspring from a single parent – leads to genetically identical offspring.
Binary fission produces two daughter cells genetically identical to the parent cells.
Binary fission occurs in prokaryotes.

33. Environment determines which form of reproduction is most advantageous
Asexual reproduction is an advantage in consistently favorable conditions.
Sexual reproduction is an advantage in changing conditions.

34. Some eukaryotes reproduce by mitosis.
Budding forms a new organism from a small projection growing on the surface of the parent.
Fragmentation is the splitting of the parent into pieces that each grow into a new organism.
Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.

35. 5.5 – Multicellular Life Key Concept:
Cells work together to carry out complex functions.

36. Multicellular organisms depend on interactions among different cell types.
Tissues are groups of cells that perform a similar function.
Organs are groups of tissues that perform a specific or related function.
Organ systems are groups of organs that carry out similar functions.

37. Specialized cells perform specific functions.
Cells develop into their mature forms through the process of cell differentiation.
Cells differ because different combinations of genes are expressed.
A cell’s location in an embryo helps determine how it will differentiate.