CHAPTER 8:

CELL GROWTH AND

DIVISION8-1: CELL GROWTH

8-2: CELL DIVISION: MITOSIS AND CYTOKINESIS

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LEARNING OBJECTIVES

You should be able to:

• Give two physical reasons why mitosis must occur.

• Draw a chromosome and determine chromosome number.

• Identify, draw, and describe each stage of the cell cycle.

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CELL GROWTH

Cells divide rather than get larger because…….

1. Demands on DNA would be too great.

2. Cell would have trouble moving food and waste across the cell membrane.

3

If a cell got too large, it would be more difficult to

get oxygen in and waste products out.

Volume increases faster than surface area.

4

If a cell got too large, it would be more difficult to

get oxygen in and waste products out.

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Volume increases faster than surface area.

If a cell got too large, it would be more difficult to

get oxygen in and waste products out.

Diffusion is slow over long distances.

http://www.physiologyweb.com/calculators/diffusion_time_calculator.html 6

Distance of DiffusionApproximate Time

Required

10 nm 23.8 ns

50 nm 595 ns

100 nm 2.38 μs

1 μm 238 μs

10 μm 23.8 ms

100 μm 2.38 s

1 mm 3.97 min

1 cm 6.61 hours

10 cm 27.56 days

CHROMOSOMES

• Each organism has a specific number of chromosomes.

• During cell division, chromatin condenses into chromosomes.

• In order for each cell to get the right number the chromosomes have to replicate 7

PARTS OF A CHROMOSOME

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Chromatid: one copy of a newly copied chromosome; still joined to original chromosome by centromere

HOW TO DRAW A CHROMOSOME

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On whiteboard

CHROMOSOMES: COUNT CENTROMERES!

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CHROMOSOMES: COUNT CENTROMERES!

https://datbootcamp.com/biology-strategy/chromosome-and-chromatid-numbers-during-mitosis-and-meiosis/ 11

STOP!

Please copy down Fig 8-10 in your notes before proceeding.

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OUTLINE OF TODAY’S TOPICS

• Cell Cycle

- Interphase

- Cell Division

- Mitosis

- Prophase

- Metaphase

- Anaphase

- Telophase

- Cytokinesis

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THE CELL CYCLEThe series of events that cells go through as they grow and

divide.

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INTERPHASE

G1 – Growth phase #1.

Cells increase in size and make new proteins and organelles.

S – Synthesis.

Chromosomes are replicated.

G2 – Growth Phase #2

Cell division organelles are produced. Short phase.

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INTERPHASE

• During interphase, chromosomes in uncondensed form

• “X” structure not visible

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OUTLINE OF TODAY’S TOPICS

• Cell Cycle

- Interphase

- Cell Division

- Mitosis

- Prophase

- Metaphase

- Anaphase

- Telophase

- Cytokinesis

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CELL DIVISION

Why do cells divide?• Growth, repair• Make identical copies of each

other

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CELL DIVISION

Two Steps:

1. Mitosis – division of the nucleus. Divided into 4 phases.

2. Cytokinesis – division of the cytoplasm.

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OUTLINE OF TODAY’S TOPICS

• Cell Cycle

- Interphase

- Cell Division

- Mitosis

- Prophase

- Metaphase

- Anaphase

- Telophase

- Cytokinesis

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PROPHASE

• Chromosomes condense (are visible)• Centrioles separate• Spindle fibers form• Nuclear membrane breaks down.

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METAPHASE

• Chromosomes line up in the middle of the cell

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ANAPHASE

• Chromosomes are pulled apart/away from each other.

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TELOPHASE• The opposite of prophase occurs.

• Chromosomes disappear back to chromatin

• Nuclear membrane reforms

• Spindle fibers break apart and disappear

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CYTOKINESIS

• Cytokinesis occurs right after Mitosis and is the division of the cytoplasm.

• Result: two daughter cells!

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OUTLINE OF TODAY’S TOPICS

• Cell Cycle

- Interphase

- Cell Division

- Mitosis

- Prophase

- Metaphase

- Anaphase

- Telophase

- Cytokinesis

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CAN YOU TELL THE PHASE?

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HOMEWORK

• Worksheet (on website: print out and complete, or simply write down answers)

• Review stages of mitosis, or you will be confused next class!

• Watch amoeba sisters video

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