chapter 8 cell growth. in most cases, a living thing grows because it produces more and more cells
TRANSCRIPT
Chapter 8
Cell Growth
In most cases, a living thing grows because it produces more and more cells
Limits of Cell Growth
Number 1Cell membrane- food oxygen and water enter and wastes leave
How fast things enter and leave depends on the surface area
How fast products are used up and waste is produced depends on the volume
Fig 8-2Surface Area and volume do not increase at the same rate so this is a problem
Number 2All the information a cell needs to survive and function is stored in the DNAWhen a cell is small enough RNA is made to make all the proteins a cell needs
As a cell gets bigger it does not make more RNA so there is an information crisisAs the cell grows there is not enough RNA to support its growthThe cell becomes inefficient
The Solution: Cell Division
The process where by the cell divides into two daughter cellsDraw picture in notes
Rates of Cell GrowthE. coli – divides every 30 minutes1 day – 14kg mass3 days – mass of earth
Ideal conditions do not last long
Controls on Cell GrowthCell behavior – cell growth and cell division are carefully controlledHeart and nervous system – cells rarely divide
Skin and digestive tract – cells divide through life
When cells come in contact with other cells they stop growing Scientists are still working on why this is true
Cell growth can be turned on Example – a cut, broken boneCell growth stops when fixed
Uncontrolled Cell GrowthResults are severeCancer – disorder where cells have lost the ability to control their own growth
8-2 Cell Division: Mitosis and Cytokinesis
Eukaryotic CellsNucleus and membrane bound organellesEukaryotic cells divide in two steps
1. Mitosis – the process by which the nucleus of a cell is divided into 2 nuclei, each with the same number and kinds of chromosomes as the parent cell
2. Cytokinesis – process of the cytoplasm dividing to form 2 new cells
The process is complex
1.Large amounts of DNA need to be separated.2.Each cell needs one copy of a chromosome
ChromosomesStructures in the cell that contain the genetic information that is passed from one generation to the next
The cells of different organisms contain different numbers of chromosomesHumans – 46Goldfish – 94Dog – 78Cat – 32
Chromosomes are made of chromatin.Chromatin is made of DNA and proteins.
When a cell is not dividing chromatin is lose and spread outWhen a cell is going to divide chromatin condenses and chromosomes become visible
The proteins in chromatin help in the folding of DNA.Helps it fit and keeps it organized.Total length of DNA 10,000x the length of a chromosome
HistonesCircular proteins that the DNA is wrapped around
NucleosomeBead like structures of DNA wrapped around a few histones
Chromosome StructureReady to divide
DNA replicatedChromosomes become visible by condensing
The structure of eukaryotic chromosomesThe structure of eukaryotic chromosomes
Centromere
Chromosome
Sister chromatids
Supercoil within chromosome
Continued coiling within supercoil
Histone H1
Nucleosome
DNA
The chromosome has two identical parts – 2 Chromatids
The chromosome has two identical parts – 2 Chromatids
The two chromatids are often called sister chromatidsCentromere – holds sister chromatids together
The Cell Cycle
The period of time from one mitosis to the nextA cell grows, prepares for division, and divides to form two daughter cellsIncludes mitosis
Mitosis – M phase `
InterphaseG1 – growth and activityS- DNA replicationG2 – growth and activity
Some cells in the body go through the cell cycle every 6 hoursSome cells never do (nerve and muscle)
InterphaseLongPeriod between cell divisions3 phases – G1, S, G2G1 – (gap1) – growth and development
S (DNA synthesis phase) – replicationProteins associated with chromosomes are also madeG2- gap 2 – shortest phaseSynthesis of materials needed for cell division
During interphase the cell is activeProteins are made DNA is copiedATP is made and used Cells that are specialized do their thingExample - secretion
Do NowWhat are the 2 phases of the cell cycle?
What happens in g1?What happens in S phase?What happens in the g2 phase?
What is chromatin?What are histones and nucleosomes?
What do uncopied chromosome s look like?What do copied chromosomes look like?How many chromosomes do humans have?
Mitosis is divided into 4 stages.
Prophase (Ready)Metaphase (Middle)Anaphase (away)Telophase (two)
ProphaseLongest phase50-60% of total mitosis timeChromosomes become visible – coil tightlyCentrioles separate and move to opposite sides
Chromosomes attach to the spindleNucleolus disappearsNuclear envelope breaks down
SpindleMeshlike structure that develops from the centriolesHelps chromosomes move
MetaphaseShortest – few minutesChromosomes line up at the center of the cell
AnaphaseCentromeres that join sister chromatids splitSister chromatids separates into individual chromosomesChromosomes separate into two groups near the poles
Over when chromosomes separate
TelophaseChromosomes loosen up – go back to chromatinOccurs in the area where the nucleus will formNuclear envelope reformsNucleolus becomes visibleMitosis is over
CytokinesisLast step in cell divisionTwo nuclei form – each with a set of chromosomesCytokinesis – division of the cytoplasm
Animal Cells – cell membrane pinches inPlant cells – cell plate forms down the middleThe cell wall forms in the cell plate
Plant Cell undergoing Mitosis
Mitosis Movie
9-3 MeiosisA type of cell division that gametes (eggs and sperm) undergo
A cell has two copies of each chromosome.Humans have 46 chromosomes or 23 pairs.
Homologous ChromosomesTwo chromosomes that make up a pairCarry the same types of informationOne originally came from mom and one originally came from dad
DiploidA cell with pairs of chromosomesOne from mom and one from dad2NDiploid number for humans is 46
HaploidA single set of chromosomes1N
AutosomesBody cell chromosomesHumans have 22 pairs
Sex ChromosomesX and YHumans have twoFemales have 2 X chromosomesMales have an X and Y chromosome
KaryotypeA picture of all of the chromosomes found in one cell.Can be used to determine gender and genetic diseases.
Meiosis2N produces 1NProcess of reduction division in which the number of chromosomes per cell is cut in half2 rounds of cell divisionMeiosis I and Meiosis IIProduces gametes (eggs and sperm)
Meiosis I
Prophase IMetaphse IAnaphase ITelophase I
Tetrad
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Prophase IIMetaphase IIAnaphase IITelophase II
Telophase II produces gametes (IN) (eggs or sperm)
Meiosis II
