Chapter 8: Cell Growth and Division 8-2: Cell division: Mitosis and cytokinesis

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.

Cell Growth Cells divide rather than get larger because……. Demands on DNA would be too great. Cell would have trouble moving food and waste across the cell membrane.

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.

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.

Approximate Time Required If a cell got too large, it would be more difficult to get oxygen in and waste products out. Distance of Diffusion Approximate 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 Diffusion is slow over long distances. http://www.physiologyweb.com/calculators/diffusion_time_calculator.html

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

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

How to Draw a Chromosome On whiteboard

Chromosomes: count centromeres!

Chromosomes: count centromeres! https://datbootcamp.com/biology-strategy/chromosome-and-chromatid-numbers-during-mitosis-and-meiosis/

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

Outline of Today’s topics Cell Cycle Interphase Cell Division Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis

The Cell Cycle The series of events that cells go through as they grow and divide.

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.

Interphase During interphase, chromosomes in uncondensed form “X” structure not visible

Outline of Today’s topics Cell Cycle Interphase Cell Division Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis

Cell Division Why do cells divide? Growth, repair Make identical copies of each other

Cell Division Two Steps: 1. Mitosis – division of the nucleus. Divided into 4 phases. 2. Cytokinesis – division of the cytoplasm.

Outline of Today’s topics Cell Cycle Interphase Cell Division Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis

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

Metaphase Chromosomes line up in the middle of the cell

Anaphase Chromosomes are pulled apart/away from each other.

Telophase The opposite of prophase occurs. Chromosomes disappear back to chromatin Nuclear membrane reforms Spindle fibers break apart and disappear

Cytokinesis Cytokinesis occurs right after Mitosis and is the division of the cytoplasm. Result: two daughter cells!

Outline of Today’s topics Cell Cycle Interphase Cell Division Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis

Can you tell the phase?

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