Chapter 8 Cell 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 ’9”, Bao Xishun and his 5’6” wife… most people with acromegalic gigantism eventually die because of complications from heart problems. "Keeping the blood going round such an enormous circulation becomes a huge strain for the heart,"

What would happen? What would happen? Calculate ratio of surface area to volume L * W * # of sides= surface area L * W * H= Volume Practice 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 SA 1*1*1=1 V Ratio 6:1 3*3*6=54 SA 3*3*3=27 V Ratio 54:27 reduce… 2:1 The 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 DNA The 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 mitosis 4 sections of the cell cycle: G phases, S phase, mitosis, cytokinesis Cell Division Mitosis Division of the nucleus Cytokinesis Division of the cytoplasm

In Bacteria …prokaryotes Have circular DNA And only 1 piece of DNA called plasmid The 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 nucleus Chromosomes are made up of DNA and proteins (called histones)

Centromere is made of protein Spindle fibers are made of microtubules sister 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 Interphase 1. G1- cell grows, and makes new proteins and organelles 2. S phase- DNA is replicated 3. G2- molecules and organelles needed for cell division are produced.

Now ready for Mitosis PMAT Prophase- longest, chromosomes become visible/ centrioles go to the poles Spindle fibers start to form Nuclear envelope starts to break down

Mitosis…. Metaphase (middle) Last only a few minutes Chromosomes line up across the MIDDLE of the cell Centromeres connect to the spindle fibers

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

Mitosis Telophase (the peanut) Chromosomes begin to disappear from view Nuclear envelope re- forms Spindles break apart Nucleolus reforms …end mitosis

Cytokinesis Nucleus 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 parts In plants cell plate eventually becomes the cell wall Cell plate >

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 stop A 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)

Cancer A 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 tumors Sometimes these cells break free and spread throughout the body These 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 tobacco Anything 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: 46 Fruit flies: 8 Carrots: 18 **worksheet

Haploid vs Diploid Haploid: half Diploid: Double But first figure out where you are at? Body cell(regular cell) is already Diploid Sperm/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…