Notes Chapter 10 Cell Growth and Division

Why do cells divide rather than continuing to grow indefinitely?

Cell growth… Cell growth… - the larger a cell becomes, the more demands the cell places on its DNA and the more trouble it has moving enough nutrients and wastes across the membrane.

The volume and mass of a cell increases much more rapidly than the surface area…causing the ratio of surface area to volume (or mass) to decrease.

“Small town” getting larger… “Small town” getting larger… - not enough books in library (information – DNA) - has only a 2 lane main street (more traffic means slower movement)

Cell Cycle: cell growth and division – separating the cell contents into 2 equal parts Before a cell become too large… it divides, forming two daughter cells.

Cell Cycle

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

chromosomes Made of DNA (which carries the genetic code) and protein Made of DNA (which carries the genetic code) and protein

Chromosomes are not visible except during cell division …otherwise the DNA and proteins are spread throughout the nucleus Chromosomes are not visible except during cell division …otherwise the DNA and proteins are spread throughout the nucleus At the beginning of cell division, chromosomes condense and are visible At the beginning of cell division, chromosomes condense and are visible

chromatid One of 2 identical “sister” parts of a duplicated chromosome One of 2 identical “sister” parts of a duplicated chromosome

centromere Area where the chromatids of a chromosome are attached Area where the chromatids of a chromosome are attached

Quick Quiz What is this called? What is this called? What is each individual “side” called? What is each individual “side” called? What is the point of attachment called? What is the point of attachment called?

Student Activity You are going to make a Cell Cycle flip book. You’ll need 3 sheets of paper.

(We’re only using 3 sheets of paper… not 4.) Staple twice at the top… near the crease.

Flip Book Cont… At the bottom edge of the top paper… write “Interphase”. You are going to draw a picture and take notes about interphase on this top page. At the bottom edge of the top paper… write “Interphase”. You are going to draw a picture and take notes about interphase on this top page.

interphase An “in-between” period of the cell cycle that separates each division of the cell An “in-between” period of the cell cycle that separates each division of the cell

Interphase - the longest phase of the cell cycle Interphase - the longest phase of the cell cycle Has three phases: Has three phases: G 1 – cell growth G 1 – cell growth S – DNA replication (and proteins) S – DNA replication (and proteins) G 2 – preparation for mitosis – shortest phase of interphase – many organelles and molecules needed for cell division are produced. G 2 – preparation for mitosis – shortest phase of interphase – many organelles and molecules needed for cell division are produced.

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

Flip Book Cont… At the bottom of the second page… write “Prophase”. At the bottom of the second page… write “Prophase”. You are going to draw and take notes about Prophase on the second page. You are going to draw and take notes about Prophase on the second page.

prophase Longest phase of mitosis (50% to 60% of time of mitosis) Longest phase of mitosis (50% to 60% of time of mitosis) Chromosomes become visible. Chromosomes become visible. Centrioles separate and take up positions on opposite poles (NOT in plants). Centrioles separate and take up positions on opposite poles (NOT in plants). Spindle fibers (microtubules that help separate chromosomes) are formed. Spindle fibers (microtubules that help separate chromosomes) are formed. Nucleolus disappears and the nuclear envelope breaks down. Nucleolus disappears and the nuclear envelope breaks down. tm tm tm tm

Flip Book Cont… At the bottom of the third page… write “Metaphase”. At the bottom of the third page… write “Metaphase”.

metaphase Chromosomes line up across the equator of the cell (middle). Chromosomes line up across the equator of the cell (middle). Microtubules connect the centromere of each chromosome to the 2 poles of the spindle. Microtubules connect the centromere of each chromosome to the 2 poles of the spindle. mitosis.htm mitosis.htm mitosis.htm mitosis.htm

Flip Book Cont… At the bottom of the fourth page write “Anaphase”. At the bottom of the fourth page write “Anaphase”.

anaphase Centromeres that join the sister chromatids split. Centromeres that join the sister chromatids split. Sister chromatids separate. Sister chromatids separate. Chromosomes move until they separate into 2 groups near the poles. Chromosomes move until they separate into 2 groups near the poles. tosis.htm tosis.htm

Flip Book Cont… At the bottom of the fifth page write “Telophase”. At the bottom of the fifth page write “Telophase”.

telophase Chromosomes, that were condensed and distinct, begin to disperse (disappear). Chromosomes, that were condensed and distinct, begin to disperse (disappear). Nuclear envelope re-forms around cluster of chromosomes. Nuclear envelope re-forms around cluster of chromosomes. Spindle breaks apart. Spindle breaks apart. sis.htm sis.htm

Flip Book Cont… At the bottom of the sixth page write “Cytokinesis”. At the bottom of the sixth page write “Cytokinesis”.

cytokinesis Division of the cytoplasm Division of the cytoplasm Animal vs Plant Animal vs Plant

daughter cells

Cell Division Overview anmito.htm anmito.htm

Cell Cycle Overview

Mitosis Overview

Regulating cell division… cyclins – proteins that regulate the timing of the cell cycle (p ) When an injury such as a cut in the skin occurs, cells at the edge of the cut will divide rapidly. When an injury such as a cut in the skin occurs, cells at the edge of the cut will divide rapidly. When the healing process nears completion, the rate of cell division slows down and then returns to normal. When the healing process nears completion, the rate of cell division slows down and then returns to normal.

Uncontrolled cell growth… cancer – a disorder in which some of the body cells lost the ability to control growth

Cancer cells do not respond to the signals that regulate the growth of most cells… Cancer cells do not respond to the signals that regulate the growth of most cells…

Cancer cells divide uncontrollably and form tumors. Cancer cells may break loose from tumors and spread throughout the body.