Chapter 8Cell Growth and Division

Biology

10-1 Cell Growth

Adults don’t have bigger cells than kids… they just have MORE of them

Why don’t cells just grow bigger?

DNA overload….DNA would need extra copies to handle “information demand”Too difficult to get enough nutrients and oxygen IN and waste products OUT

The world's tallest man in 2007 7’9”,

Bao Xishun and his 5’6” wife…most peoplewith acromegalic gigantism eventually die because of complications fromheart problems. "Keeping the blood going round such an enormous circulationbecomes a huge strain for the heart,"

What would happen?What would happen? Calculate ratio of surface area to volume

L * W * # of sides= surface areaL * W * H= VolumePractice problem: if cell was a cube and its sides were 1cm each ….figure SA?Figure V…What if the cell were 3cm? SA? V?What is the ratio?

Volume increases faster than surface area

1*1*6=6 SA1*1*1=1 VRatio 6:1

3*3*6=54 SA3*3*3=27 V

Ratio 54:27 reduce… 2:1The decrease in ratio of SA to V- makes

it harder for the cell to move needed products in and out.

Cell division solves…

The problem of information storage… because each daughter cell gets it’s own DNAThe problem of being too big and inefficient because although the cell grows some… daughter cells will still be smaller than the parent

10-2 Cell Division : is mitosis4 sections of the cell cycle: G phases, S phase, mitosis, cytokinesis

Cell Division

Mitosis Cytokinesis

Division of the nucleusDivision

of the cytoplasm

In Bacteria …prokaryotes

Have circular DNAAnd only 1 piece of DNA called plasmidThe process by which bacteria reproduce is called binary fission (not mitosis)

10-2 Cell Division In eukaryotes the chromosomes carry the genetic information and they live inside the nucleusChromosomes are made up of DNA and proteins (called histones)

Centromere is made of proteinSpindle fibers are made of microtubulessister chromatids are duplicate halves

Karyotype- Tells # of chromosomes in that body cell

Growth & Repair

Interphase

Baby Cell (daughter cell) grows and matures here…and eventually is mature enough to divide a.k.a.…time in between cell division

3 steps of Interphase1. G1- cell grows, and makes new

proteins and organelles2. S phase- DNA is replicated3. G2- molecules and organelles needed

for cell division are produced.

Now ready for MitosisPMAT

Prophase- longest, chromosomes become visible/ centrioles go to the polesSpindle fibers start to formNuclear envelope starts to break down

Mitosis….

Metaphase (middle)Last only a few minutesChromosomes line up across the MIDDLE of the cellCentromeres connect to the spindle fibers

Mitosis…

Anaphase (the fingers)Centromeres split , splitting chromosomes into 2 setsChromosomes move away from each other to the poles- being pulled by spindle fibers

Mitosis

Telophase (the peanut)Chromosomes begin to disappear from viewNuclear envelope re-formsSpindles break apartNucleolus reforms…end mitosis

CytokinesisNucleus and contents have split but what about the rest of the cell….?Cell membrane is drawn inward until cytoplasm is eventually pinched into two equal partsIn plants cell plate eventually becomes the cell wall

Cell plate >

http://www.biostudio.com/d_%20Mitosis.htm

10-3 Regulating the Cell Cycle

Cell growth and cell division are carefully controlled

Cells grow when there is space , then when they bump into other cells they stopA cut in your hand?

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What signals the cell to start dividing?

A set of proteins called cyclins control the timing of cell division…Internal Regulators- tell cell to divide based on what is happening inside the cell (PMAT timing)External Regulators- tell cell to divide based on what is happening outside the cell (wound healing , embryonic development)

CancerA disorder in which some of the body’s own cells (whose DNA is damaged) lose the ability to control growth…Cells grow out of control and form masses called tumorsSometimes these cells break free and spread throughout the bodyThese cells lack the proteins that tell them to stop growing and ignore the bordering cells telling them to stop

Causes of Cancer

Viral Infection (commercial)Radiation (sun, x-rays ) Smoking tobaccoAnything known to cause cancer cells to develop is called a carcinogen….

Identifying the Number of Chromosomes…

Not all living things have the same number of chromosomes..Humans: 46Fruit flies: 8Carrots: 18**worksheet

Haploid vs Diploid

Haploid: half Diploid: Double

But first figure out where you are at?Body cell(regular cell) is already DiploidSperm/egg cell (sex cell) is already Haploid

Differences between animal and plant cells-

Plants have a cell wall and a cell membrane- so when they pinch…it’s called a cell plate.The cell plate becomes the cell membrane – then the cell wall develops next.

Cell plate >

The End…