Notes Chapter 10 Cell Growth and Division. Why do cells divide rather than continuing to grow indefinitely?

NotesNotes Chapter 10 Chapter 10

Cell Cell GrowthGrowth and and DivisionDivision

Why do cells Why do cells dividedivide rather than rather than continuing to grow indefinitely?continuing to grow indefinitely?

Cell growth…Cell growth… - the larger a cell becomes, the more - the larger a cell becomes, the more demands the cell places on its demands the cell places on its DNADNA and the more trouble it has and the more trouble it has movingmoving enough nutrientsenough nutrients and and wasteswastes across the membrane.across the membrane.

The The volumevolume and and massmass of a cell of a cell increasesincreases much much moremore rapidly than the rapidly than the surfacesurface areaarea…causing the ratio of surface area …causing the ratio of surface area to volume (or mass) to decrease.to volume (or mass) to decrease.

““Small townSmall town” getting larger…” getting larger…- not enough books in library - not enough books in library (information – (information – DNADNA))

- has only a 2 lane main street - has only a 2 lane main street (more traffic means (more traffic means slower slower movementmovement))

CellCell CycleCycle: : cell cell growthgrowth and and divisiondivision – separating – separating the cell contents into 2 equal partsthe cell contents into 2 equal parts

Before a cell become too large… it Before a cell become too large… it divides, forming two daughter cells.divides, forming two daughter cells.

Cell CycleCell Cycle

Before a cell divides… it must duplicate it’s Before a cell divides… it must duplicate it’s genetic material…genetic material…

chromosomeschromosomesMade of Made of DNADNA (which carries the (which carries the

genetic code) and genetic code) and proteinprotein

Chromosomes are not visible except Chromosomes are not visible except during during cell divisioncell division …otherwise the DNA …otherwise the DNA and proteins are spread throughout the and proteins are spread throughout the nucleus nucleus

At the beginning of At the beginning of cell divisioncell division, , chromosomes condense and are visiblechromosomes condense and are visible

chromatidchromatidOne of 2 identical “sister” parts of One of 2 identical “sister” parts of

a duplicated a duplicated chromosomechromosome

centromerecentromereArea where the Area where the chromatidschromatids of a of a

chromosomechromosome are attached are attached

Quick QuizQuick Quiz What is this called?What is this called?

What is each What is each individual “side” individual “side” called?called?

What is the point of What is the point of attachment called?attachment called?

Student ActivityStudent Activity

You are going to make a Cell Cycle flip You are going to make a Cell Cycle flip book.book.

You’ll need 3 sheets of paper.You’ll need 3 sheets of paper.

(We’re only using 3 sheets of paper… not 4.)(We’re only using 3 sheets of paper… not 4.)

Staple twice at the top… near the crease.Staple twice at the top… near the crease.

Flip Book Cont…Flip Book Cont…At the bottom edge of the top paper… At the bottom edge of the top paper…

write “Interphase”. You are going to draw a write “Interphase”. You are going to draw a picture and take notes about interphase on picture and take notes about interphase on this top page.this top page.

interphaseinterphaseAn “An “in-betweenin-between” period of the cell ” period of the cell

cycle that separates each division cycle that separates each division of the cellof the cell

InterphaseInterphase - the longest phase of the cell - the longest phase of the cell cyclecycle

Has three phases:Has three phases:

GG11 – cell growth – cell growth

S – DNA replication (and proteins)S – DNA replication (and proteins)

GG22 – preparation for mitosis – shortest phase of – preparation for mitosis – shortest phase of interphase – many organelles and molecules interphase – many organelles and molecules needed for cell division are produced.needed for cell division are produced.

mitosismitosis

Process of cell division... Dividing Process of cell division... Dividing a cell’s nucleus.a cell’s nucleus.

Flip Book Cont…Flip Book Cont…At the bottom of the second page… write At the bottom of the second page… write

“Prophase”.“Prophase”.You are going to draw and take notes You are going to draw and take notes

about Prophase on the second page.about Prophase on the second page.

prophaseprophase• Longest phase of mitosis (50% to Longest phase of mitosis (50% to

60% of time of mitosis)60% of time of mitosis)

• Chromosomes become visible.Chromosomes become visible.

• CentriolesCentrioles separate and take up separate and take up positions on opposite poles (positions on opposite poles (NOTNOT in plants).in plants).

• Spindle fibersSpindle fibers (microtubules that (microtubules that help separate chromosomes) are help separate chromosomes) are formed.formed.

• Nucleolus disappears and the Nucleolus disappears and the nuclear envelope breaks down.nuclear envelope breaks down.

• http://http://www.cellsalive.com/mitosis.htmwww.cellsalive.com/mitosis.htm

Flip Book Cont…Flip Book Cont…At the bottom of the third page… write At the bottom of the third page… write

“Metaphase”.“Metaphase”.

metaphasemetaphase Chromosomes line up Chromosomes line up

across the equator of the across the equator of the cell (middle).cell (middle).

Microtubules connect the Microtubules connect the centromere of each centromere of each chromosome to the 2 chromosome to the 2 poles of the spindle.poles of the spindle.

http://http://www.cellsalive.com/mitoswww.cellsalive.com/mitosis.htmis.htm

Flip Book Cont…Flip Book Cont…At the bottom of the fourth page write At the bottom of the fourth page write

“Anaphase”.“Anaphase”.

anaphaseanaphase Centromeres that join the Centromeres that join the

sister chromatids split.sister chromatids split.

Sister chromatids Sister chromatids separate.separate.

Chromosomes move until Chromosomes move until they separate into 2 they separate into 2 groups near the poles. groups near the poles.

http://http://www.cellsalive.com/mitoswww.cellsalive.com/mitosis.htmis.htm

Flip Book Cont…Flip Book Cont…At the bottom of the fifth page write At the bottom of the fifth page write

“Telophase”.“Telophase”.

telophasetelophase Chromosomes, that were Chromosomes, that were

condensed and distinct, condensed and distinct, begin to disperse begin to disperse (disappear).(disappear).

Nuclear envelope re-forms Nuclear envelope re-forms around cluster of around cluster of chromosomes.chromosomes.

Spindle breaks apart.Spindle breaks apart.

http://http://www.cellsalive.com/mitosis.www.cellsalive.com/mitosis.htmhtm

Flip Book Cont…Flip Book Cont…At the bottom of the sixth page write At the bottom of the sixth page write

“Cytokinesis”.“Cytokinesis”.

cytokinesiscytokinesisDivision of the Division of the cytoplasmcytoplasm

Animal vs PlantAnimal vs Plant

daughter cellsdaughter cells

Cell Division OverviewCell Division Overviewhttp://www.cellsalive.com/mitosis.htmhttp://www.cellsalive.com/mitosis.htm

http://www.johnkyrk.com/mitosis.htmlhttp://www.johnkyrk.com/mitosis.html

http://web.grcc.edu/biosci/pictdata/mitosis/plhttp://web.grcc.edu/biosci/pictdata/mitosis/planmito.htmanmito.htm

Cell Cycle OverviewCell Cycle Overview

http://www.cellsalive.com/cell_cycle.htmhttp://www.cellsalive.com/cell_cycle.htm

Mitosis OverviewMitosis Overview

RegulatingRegulating cell division… cell division…

cyclinscyclins – proteins that regulate the timing of the – proteins that regulate the timing of the cell cycle (p. 250-251)cell cycle (p. 250-251)

When an injury such as a cut in the skin occurs, When an injury such as a cut in the skin occurs, cells at the edge of the cut will divide rapidly. cells at the edge of the cut will divide rapidly.

When the healing process nears completion, the When the healing process nears completion, the rate of cell division slows down and then returns rate of cell division slows down and then returns to normal.to normal.

Uncontrolled Uncontrolled cell growth…cell growth…

cancercancer – a disorder in which some of – a disorder in which some of the body cells lost the ability to the body cells lost the ability to control growthcontrol growth

CancerCancer cells cells do notdo not respondrespond to the signals to the signals that regulate that regulate the growth of the growth of most cells…most cells…

CancerCancer cells divide cells divide uncontrollablyuncontrollably and and form form tumorstumors. .

CancerCancer cells may break loose from cells may break loose from tumorstumors and and spreadspread throughout the throughout the body.body.