Cellular Reproduction Chapter 9 Cellular Reproduction

Why do cells need to reproduce?

Why are cells so small?

How is the surface area represented in a cell? What is Surface Area? How is the surface area represented in a cell?

What happens when the volume of a cell increases? What is Volume? What happens when the volume of a cell increases?

Mini-Lab 9.1 Investigate Cell Size Cell Surface Area (L x W x 6) Cell Volume (L x W x H) Cell 1 0.00002 m Cell 2 0.001 m Cell 3 2.5 cm (0.025 m) Cell 4 30 cm (0.3 m) Cell 5 15 m

Cell Cell Size Cell Surface Area (L x W x 6) Cell Volume (L x W x H) SA : V Cell 1 0.00002 m 0.0000000024 0.000000000000008 300, 000 : 1 Cell 2 0.001 m 0.000006 0.000000001 6000 : 1 Cell 3 2.5 cm (0.025 m) 0.00375 0.000015625 240 : 1 Cell 4 30 cm (0.30 m) 0.54 0.027 20 : 1 Cell 5 15 m 1350 3375 1 : 2.5

Cell Cell Size Cell Surface Area (L x W x 6) Cell Volume (L x W x H) SA : V Cell 1 0.002 cm Cell 2 0.1 cm Cell 3 2.5 cm Cell 4 30 cm Cell 5 1500 cm

Cell Cell Size Cell Surface Area (L x W x 6) Cell Volume (L x W x H) SA : V Cell 1 0.002 cm 0.000024 0.000000008 3000:1 Cell 2 0.1 cm 0.06 0.001 60:1 Cell 3 2.5 cm 37.5 15.625 2.4:1 Cell 4 30 cm 5400 27000 0.2:1 Cell 5 1500 cm 13,500,000 3,375,000,000 0.004:1

Limits to Cell Size Smaller cells can better: Exchange nutrients and expel wastes across the plasma membrane. higher surface area to volume ratio (SA:V) Transport substances within the cell. diffusion motor proteins along cytoskeleton Communicate instructions for cellular functions. signal proteins

Events of the Cell Cycle During the cell cycle, the cell grows, replicates its DNA, and divides into two daughter cells. DNA synthesis takes place during the S phase. Cell division takes place during the M phase. G1 and G2 are gap phases.

The Cell Cycle The entire process of growing and dividing Repeated continuously Creates two cells from one cell Normal animal cells – takes 12-24 hours 3 main stages: Interphase Mitosis Cytokinesis

Stages of Cell Cycle Interphase Includes G1, S, G2 Followed by Cell Division Includes Mitosis and Cytokinesis

Interphase Period of time during which the cell, 3 parts (substages) grows and develops, carries out cellular functions, and makes copies of its DNA in preparation for cell division 3 parts (substages) G1 – Gap 1 S – Synthesis G2 – Gap 2

Stages of Interphase Gap 1 (G1) Immediately after cell divides Cell is growing and carrying out normal functions Cell is preparing to replicate DNA Synthesis Phase (S) Cell copies its DNA in preparation for cell division Gap 2 (G2) Cell prepares for division of its nucleus Makes proteins needed for cell division

Cell Division When a cell reaches its maximum size, the nucleus initiates cell division. Cell division – the splitting of a single cell into two cells. ‘Big Bang’ by M. Ormestad ©2006 All rights reserved

Cell Division Cells divide so that an organism… can grow. increases mass of organism changes organism - differentiation can repair damaged cells and tissues. regeneration maintenance can reproduce.

Mitosis (Cell Division) Stage of cell cycle where the nucleus divides Includes four stages: Prophase Metaphase Anaphase Telophase

Cytokinesis (Cell Division) Process where the cell’s cytoplasm divides and creates a new cell

Chapter 9.2 Mitosis and Cytokinesis

Mitosis & Cytokinesis Mitosis Cytokinesis the cell’s nuclear material divides 4 parts (substages) Cytokinesis the cell cytoplasm is divided into two daughter cells

Genetic Material in the Cell Question 1: In what stage of the cell cycle is the DNA copied? Answer 1: Synthesis Question 2: Why is this important? Answer 2: It prepares the cell for cell division Question 3: How is DNA organized in a cell? Hint: Answer: Chromosomes

Chromosomes Structures that contain the genetic material of an organism Only visible during mitosis Formed when chromatin is wound tightly around proteins

The DNA strands wraps around proteins called histones The continue to wrap around forming nucleosomes

For most of the cell’s life, the DNA is contained in the chromatin state In cell division, chromatin organizes into distinct chromosomes structures Chromosome Formation http://www.youtube.com/watch?v=gbSIBhFwQ4s

Chromosome Structure

Centromere Sister chromatids Structure where the sister chromatids are attached Sister chromatids Identical copies Copies created during synthesis of interphase Attached at beginning of mitosis

Stages of Mitosis Prophase Metaphase Anaphase Telophase Human cell undergoing cytokinesis from M. Pines, Inside the Cell: The New Frontier of Medical Science. U.S. Dept. of Health, Education, and Welfare, 1978.

Prophase 1st stage longest Chromatin condenses into chromsomes Nuclear membrane disintegrates Nucleolus disappears Chromosomes attach to spindle apparatus

End of Prophase Spindle apparatus forms Spindle fibers Centrioles Chromosomes attach to spindle fibers

Metaphase 2nd stage shortest sister chromatids pulled along the spindle apparatus toward the center of the cell line up along the middle, or equator

Anaphase 3rd stage sister chromatids are pulled apart spindle shorten separates chromatids into two identical sets

Telophase 4th & last stage “opposite of prophase” Chromosomes arrive at poles of spindle apparatus decondense Nuclear membrane and nucleolus reform Spindle apparatus is broken down or recycled May occur simultaneously with cytokinesis

Another Look at Mitosis

Cytokinesis Division of the cytoplasm into two daughter cells Animal cells microfilaments constrict cell membrane pinches cell in two Plant cells construct a cell plate new cell wall forms on either side of cell plate Prokaryotic cells DNA copies attach to plasma membrane plasma membrane grows and pulls DNA copies apart cell membrane pinches into two cells

Mitosis in Motion http://www.johnkyrk.com/mitosis.html http://www.cellsalive.com/mitosis.htm http://www.sci.sdsu.edu/multimedia/mitosis/navigator.html http://www.sumanasinc.com/webcontent/animations/content/ mitosis.html

Chapter 9.3 Cell Cycle Regulation

Normal Cell Cycle In eukaryotic cells, cell division driven by A protein cyclin binding to an enzyme cyclin-dependent kinase (CDK)

Normal Cell Cycle Different cyclin/CDK combinations control different activities in the cell cycle: Signals the start of the cell cycle during G1 Signals DNA replication Signals protein synthesis Signals nuclear division Signals the end of the cell cycle

Normal Cell Cycle The cell cycle also has checkpoints to monitor the cycle and stop it if something goes wrong

Abnormal Cell Cycle: Cancer Cancer is uncontrolled cell growth that occurs when there is a failure in the regulation of the cell cycle Cancer cells crowd out other normal cells and can intrude other organs; may lead to death of the organism from loss of tissue

Abnormal Cell Cycle: Cancer Cancer cells occur when mutations takes place in segments of DNA Mutation cause changes in the productions of proteins, including cyclins Substances that cause cancer are carcinogens

Apoptosis Normal, Programmed cell death Occurs in cells that are damaged beyond repair Can help protect cells from cancer

Stem Cells Cells are designed for specialized functions Stem cells are unspecialized cells that can develop into specialized cells Two types of stem cells: Embryonic Adult

Stem Cells The Nature of Stem Cells Go, Go Stem Cells http://learn.genetics.utah.edu/content/tech/stemcells/scintro/ Go, Go Stem Cells http://learn.genetics.utah.edu/content/tech/stemcells/sctypes/