1. Cell Growth and Reproduction
Section 10.1 and 10.2
Biology

2. Diffusion – diffusion slows w/larger distances
Limits to cell growth
Diffusion – diffusion slows w/larger distances
DNA – DNA can only control the needs of a small cell
Cell Size - Surface area-to-volume ratio must be high; 6/1; cell has trouble transporting materials in/out of the cell if it’s too low like 2/1

3. The larger the cell, the lower the ratio (surface area to volume), the harder to transport materials.
Solves these problems with cell division (making 2 new cells)
Cell Division – when a cell gets too large to control or function efficiently, cell division takes place

5. Cell division
10.2

6. Chromosomes
Chromosomes are carriers of our genetic material & must be copied & transmitted accurately
Chromosomes are tightly coiled chromatin.
Most of the time our chromosomes exists as chromatin (long strands of DNA wrapped around proteins called histones)

7. Cell Cycle (3 stages)
Sequence of growth (interphase), nuclear division (mitosis), and cytoplasmic division (cytokinesis) of a cell

8. Interphase (1st stage)
G1 – growth phase – cell gets bigger and develops
S – synthesis phase – DNA in nucleus is copied
G2 – growth phase – preparation for mitosis; produce more organelles, enzymes, centrioles are replicated, etc.

9. Mitosis – PMAT (2nd stage)
nuclear division
yields two daughter nuclei that are genetically identical
used for growth and healing

10. Prophase - prepare Metaphase - middle Anaphase - away
4 stages to mitosis
Prophase - prepare
Metaphase - middle
Anaphase - away
Telophase – two cells

12. Prophase
Chromatin condenses into chromosomes, 2 identical strands of DNA attached by a centromere
Centrioles move to opposite ends of the cell
Nuclear envelope and nucleolus disappear
Spindle starts to appear

13. Chromosomes line up about midway between the centrioles
Metaphase
Chromosomes line up about midway between the centrioles
Spindle fibers attach to chromosomes at centromeres

14. Centromeres are pulled apart as spindle fibers contracts
Anaphase
Centromeres are pulled apart as spindle fibers contracts
Chromatids (half of a chromosome) are pulled in opposite directions
Chromatids are pulled to opposite ends of the cell

15. Telophase Chromatids complete journey to the ends of the cell
Chromatin is formed as DNA elongates
Nuclear envelope forms around each set of DNA
Spindle disappears
Nucleoli appear in each nucleus

17. Cytokinesis (3rd stage)
Cytoplasmic Division
Begins during anaphase
In animal cells a furrow / ring starts to develop in the middle of the cell membrane (pinching of the middle)

18. Cytokinesis
In plants, you start to develop a cell plate (starts in middle of the 2 cells)
Ring contracts until it completely separates the two new nuclei and about ½ organelles into each new cell

21. Control of the Cell Cycle
cyclins (proteins) regulate cell growth
Internal regulators – only move to the next phase of the cell cycle when the previous phase is complete

22. Control of the Cell Cycle
External regulators – if there is room, a cell divides; if neighboring cells are touching, cell growth is inhibited because space is scarce

23. Cancer
Uncontrolled cell growth
Tumors are cells that do not respond to cell regulators
Cells could also become “immortal”; they don’t finish cell development and die, so new cells just build up

24. Apoptosis – programmed cell death
Normal part of development for most cells in a multi-celled organism ( billion cells die each day in the average human adult.)
Once cells stop dividing or specializing; special enzymes will break it down & scavenger WBCs come & clean up