Remember….• Cell Theory-

1. All living things are composed of one or more cells.

2. The cells is the basic unit of structure.

3. All cells come from preexisting cells.

Cell Theory #2 In Detail

• ORGANIZATION of LT– Cells -> Tissues – Tissues organize into

organs– Multiple organs work

together to for an organ system

– All systems work together for survival of the organism

Why does a cell need to divide?

IN GENERAL-• All organisms grow and change• Worn-out tissues are repaired or are replaced by

newly produced cells.

Why does a cell need to divide?

SPECIFICALLY: Cell Size Limitations1. Diffusion: short distances = efficient; long

distances = inefficient • Think running 1/4mi vs. running 24 mi.

2. DNA: must be copied and made into protein to make necessities…can only be done so fast.

• Think about copying homework for 1 class in 5 minutes vs. 7 classes in 5 minutes

http://openlearn.open.ac.uk/file.php/2815/S324_1_009i.jpg

3. Surface Area-to-Volume ratio: volume will become

to much for the PM’s surface area to handle.• Think about a city growing, but no one builds new

roads or bridges etc.= traffic jam

A Cell’s Life – Describe the cell cycle

The Cell Cycle

1. Interphase – Longest Part of Cycle – “Growing Stage” - cell grows (G1, S, G2)– carries on metabolism, spends most of its time

here. (G1, S, G2)– DNA is copied (S only)

A Cell’s Life – Describe the cell Cycle

2. Mitotic Phasea.) Mitosis : chromosomes divide

b.) Cytokinesis: cytoplasm divides into 2

HONORS• Chromatin - long strands of DNA wrapped

around histones.

• Must copy DNA

• Supercoil to form chromosomes composed of two halves called sister chromatids: exact copies of each other held together by centromeres

micro.magnet.fsu.edu/ cells/nucleus/images/chr...

How do cells reproduce/divide?

a.) Mitosis-

I. Prophase –– longest phase– Sister chromatids join – Nucleus (envelope and nucleolus)

disintegrate

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8.2 Cell Growth and ReproductionMitosis cont’

II. Metaphase –

– Chromosomes pulled to the equator (middle)

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8.2 Cell Growth and ReproductionMitosis cont’

III. Anaphase-– Chromosomes split and sister

chromatids are pulled apart to opposite poles of the cell

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8.2 Cell Growth and Reproduction

IV. Telophase- – Chromatids reach the

opposite poles (ends),

What is Cytokinesis?b.). Cytokinesis - cytoplasm divides,

cells separate into two daughter cells.

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Honors: What is cytokinesis?• Animal cells: plasma membrane

pinches in along the equator

• Plant cells: a cell plate is laid down across the cell’s equator and a cell membrane forms around each cell. New cell walls form on each side of the cell plate until separation is complete

What is the end result of Mitosis?• Two identical cells that are identical to the original

parent cell. – will carry out the same cellular processes and functions as

those of the parent cell – will grow and divide too

Specifically - • Unicellular organisms = doubled number of organisms.

Called asexual reproduction

• Multicellular organisms = growth = more tissue.

Can you find all the stages?