Chapter 10Cell Growth and Division

Cell Growth

• Key factors of cell size– Surface area – area around the cell (plasma membrane)– Volume – space inside cell

• Small cell size allows for:– Successful diffusion– Proper nutrient use– Expelling waste

• Cells increase in – Size – Number

Cell Growth Problems

• As they grow…– More demand on the DNA

– Uses resources more quickly

– Difficulty moving materials across the membrane

• Once a cell reaches its size limit, it will– Stop growing

– Divide

• Cell Division

The Cell Cycle

• One cell cycle results in two cells.

• Cells divide to keep small size and replace lost cells.

The Cell Cycle• Process cells go through as they grow and divide• Three main stages of cell cycle

1. Interphase (G1, S, G2)2. Mitosis (M phase)3. Cytokinesis (M phase)

1. Interphase: Three Sub-stages

• G1 - Gap-1– growth period just after a cell divides

• S - Synthesis – cell copies its DNA (replicates)

• G2 - Gap-2 – prepares for cell division (mitosis)

2. Mitosis (cell division)

• New cells (daughter) receives copy of parent DNA

• Chromosomes become visible

• Divided into sub-stages

3. Cytokinesis

• Method by which a cell’s cytoplasm divides (the cell splits), creating two daughter cells with identical nuclei.

Mitosis and Cytokinesis

• Two main stages of cell division

• Eukaryotic cells reproduce by:– Mitosis – the process of nuclear division– replicated DNA separates and passed to

identical daughter cells– Cytokinesis – the process of cytoplasm

division.

Chromosomes are DNA

Chromosome Parts

Chromosome Division

• When the cell divides, the chromatids separate, each new cell gets one chromatid.

Sister chromatids

Centromere

Miotic Phases

• PMAT

– Prophase

– Metaphase

– Anaphase

– Telophase

Prophase

• First phase• Longest phase• Chromatin condenses

into chromosomes (shaped like an X)

Prophase

Spindle

•Microtubules called spindle fibers form

•Spindle fibers attach at the centromere and to opposite poles

•Help to separate the chromosomes

Metaphase

• Shortest stage

• Spindles line chromosomes up in the middle of the cell

• Tension between opposite fibers maintain alignment

• Ensures that new cells have accurate copies of chromosomes

Metaphase

Anaphase

• Chromatids are pulled apart

• Spindle fibers move sister chromatids to opposite sides of the cell

Anaphase

Telophase

• Last phase

• 2 new nuclear membranes begin to reform and nuclei reappear

Telophase

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Mitosis

Cytokinesis

• Divides cytoplasm• Results in 2 cells,

each with IDENTICAL nuclei

• In plant cells, a new structure called a cell plate forms between the 2 daughter cells (instead of pinching off)

Cytokinesis

Number of Chromosomes

• If a cell has 5 chromosomes, after mitosis each new cell will have ___________ chromosomes.

• If a cell has 15 chromosomes, after mitosis each new cell will have ___________ chromosomes.

• If a cell has 10 chromosomes, after mitosis each new cell will have ___________ chromosomes.

• If a cell has 100 chromosomes, after mitosis each new cell will have ___________ chromosomes.

Cell Cycle Control

• Cells reproduce until the contact other cells, then stop growing

• This demonstrates that controls on cell growth and division can be turned on and off.

• Regulated outside of the cell

Contact Inhibition

Cell Cycle Regulation

• Cyclin is a regulating protein.

– Regulates the timing of the cell cycle

– The amount of this protein in the cell rises and falls in time with the cell cycle.

Cyclin Discovery

• Cyclins were discovered during a similar experiment to this one.

A sample of cytoplasm is removed from a cellin mitosis.

The sample is injected into a second cell inG2 of interphase.

As result, the second cell enters mitosis.

Cancer

• Cancer – uncontrolled growth rate and division

• Cancer cells grow fast because they spend less time in interphase

• Form masses called tumors

Causes of Cancer

• Mutations• Carcinogens –

substances that cause• Genetics

Stem Cells

• 2 types: unspecialized– Embryonic– Adult

Stem Cell Research

• What can stem cell research do?

Quiz Time

The cell cycle is believed to be controlled by proteins called

• spindles.

• cyclins.

• regulators.

• centrosomes.

Once a multicellular organism reaches adult size, the cells in its body

a. stop dividing.

b. grow and divide at different rates, depending on the type.

c. have the same life span between cell divisions.

d. undergo cell division randomly.

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The phase of mitosis during which the chromosomes line up across the center of the cell is • prophase.

• metaphase.

• anaphase.

• telophase.

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Cytokinesis usually occurs • at the same time as telophase.

• after telophase.

• during interphase.

• during anaphase

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DNA replication takes place during the• S phase of the cell cycle.

• G1 phase of the cell cycle.

• G2 phase of the cell cycle.

• M phase of the cell cycle.

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During mitosis, “sister” chromatids separate from one another during• telophase.

• interphase.

• anaphase.

• metaphase.

The series of events that cells go through as they grow and divide is called • the cell cycle.

• mitosis.

• interphase.

• cytokinesis.