1. Questions
Are the cells of the small plant larger or smaller than those of the larger plant? Are the cells of the small animal larger or smaller than those of the large animal.
Can you make a general statement that compares the number and size of cells in small organisms to those in large organisms.

2. 10 – 1: Cell Growth and Division

3. How do living things grow?
Grow by producing more cells. (Cells do not increase in size)
A human adult has about 10 trillion – 100 trillion cells in their entire body.
About how many cells does a newborn baby have?
Answer: Much less
Cells Dividing
Blood Lily

4. Limits to Cell Growth 2 reasons why cells divide rather than grow?
The larger cell has more trouble moving nutrients and waste across the cell membrane.
The larger the cell, the more demand the cell places on its DNA.

5. DNA “Overload” DNA is found in the nucleus of the cell
Why can’t a cell grow without limit?
When a cell grows, it does not make more copies of its DNA. If the cell grew continuously, there would be information crisis.

6. Exchanging Material
What substances may move through the cell membrane?
Answer: Food, oxygen and water enters.
Waste leaves the cell.
The rate materials exchange depends on the surface area of the cell
The rate materials are used depends on the cell’s volume (size).

7. Ratio of Surface Area to Volume
Surface to volume ratio
Volume increases faster than surface
The cell uses materials faster than it can get them in
Town analogy: A small town has only a 2 lane street. As the town grows there is more traffic on the 2 lane street.

8. Asexual Reproduction
Asexual reproduction - a single parent producing an offspring. The offspring produced are, in most cases, genetically identical to the parent.
Asexual reproduction is a simple, efficient, and rapid way for an organism to produce a large number of offspring.
Both prokaryotic and eukaryotic single-celled organisms and many multicellular organisms can reproduce asexually Ex. hydra, bacteria, yeast

9. Sexual Reproduction
In sexual reproduction, offspring are produced by the fusion of two sex cells – one from each of two parents.
The offspring produced inherit some genetic information from both parents, therefore they are genetically different.
Most animals and plants, and many single-celled organisms, reproduce sexually.

10. 10.2 The Process of Cell Division
Cells divide to form two new cells called daughter cells
This process is called cell division
Before it can occur, what has to happen? The cell replicates, or copies, all its DNA
DNA is condensed into a manageable form (chromosome) so it can be divided precisely

11. Section 10-2: Cell Division
Prokaryotes – less complicated division
Replicate DNA – divide everything up between 2 cells.
Eukaryotes – more complicated division
2 Main Stages
Mitosis – division of the nucleus
Cytokinesis – division of cytoplasm

12. Chromosomes
Chromosomes – bundled packages of DNA that contain genetic information
Every organism has a specific number of chromosomes
Fruit flies – 4
Dog - 78
Carrots – 18
How many chromosomes do humans have? 46 (23 pairs)

13. Chromosomes Chromosomes are only visible when the cell divides.
Why is this?
DNA and protein molecules are spread throughout the nucleus in the form of Chromatin. Chromatin condenses during cell division.
Before division, the chromosome (DNA) is replicated
The replicated chromosome consists of 2 identical “sister” chromatids.
One chromatid goes to each new cell
Held together near the center by centromere
Sister chromatids
Exact copies of each other
Centromere
TEM 36,000

14. Chromosomes (a closer look)
Chromatin is a complex of DNA coiled around proteins called histones
The DNA and histone molecules then form beadlike structures called nucleosomes.
The chromosome “X” shape we usually see drawn is a duplicated chromosome made of supercoiled chromatin

15. Eukaryotic Cell Cycle
The cell cycle represents the events in the life of a cell.
Interphase  Growth Phase most time spent in this phase
G1  Cell growth
S  Replication of DNA
G2  Final growth
Mitosis (M phase)  Division of the nucleus (can last hours to a few days)
4 Phases:
Prophase
Metaphase
Anaphase
Telophase

16. Mitosis – Prophase first and, longest phase
DNA condenses into chromosomes
2 centrioles (microtubules) take positions on opposite sides of the nucleus
Spindle begins to form
What is a spindle?
A fanlike microtubule structure that helps separate chromosomes.

17. Prophase cont’d Chromosomes coil more tightly Nucleolus disappears
Nuclear envelope breaks down

18. Metaphase – second phase, takes a few minutes
Chromosomes line up across middle of the cell
Microtubules connect the centromere of each chromosome to the two poles of the spindle

19. Anaphase – third phase
Centromeres that join the “sister” chromatids together split.
Chromatids separate (now individual chromosomes)
The copies move away from each other to opposite sides of the cell (2 groups)

20. Telophase – fourth, final phase
Chromosomes uncoil and relax
Nuclear envelope reforms around each cluster of chromosome
Spindle breaks down
A nucleolus becomes visible in each daughter nucleus.

21. Kinetochore
Kinetochore – a disk of protein bound to the centromere that is an attachment site for microtubules that assist in cell division

22. Cytokinesis Division of the cytoplasm
Occurs at the same time as telophase
Actin (blue) and microtubules (orange) at the end of cytokinesis in a green urchin zygote.

23. Cytokinesis - Animal Animal cells are surrounded by a cell membrane
Animal Cell  Formation of a cleavage furrow
Cleavage furrow
SEM 140
Cleavage furrow
Contracting ring of microfilaments
Daughter cells

24. Cytokinesis - Plant Plant Cell  Formation of cell plate
TEM 7,500
Cell plate forming
Wall of parent cell
Daughter nucleus
Cell wall
New cell wall
Vesicles containing cell wall material
Cell plate
Daughter cells
Plant cells are surrounded by a cell wall
Plant Cell  Formation of cell plate

25. Mitosis Animation

26. Cell Division - Prokaryotes
Prokaryote  unicellular bacteria with no nucleus
Binary Fission  DNA is replicated, cell doubles in size and splits

28. 2. 1. 5. 4. 3.

29. 2. 3. 4. 1.

30. 2. 3. 4. 5. 1. Cleavage furrow Sister chromatids separate
Haploid daughter cells forming
Sister chromatids separate 2. 3. 4. 5. 1.