Cell Cycle & Mitosis Chapter 10

Cell Growth, Division, and Reproduction Limits to Cell Size What happens when a cell increases in size? Less efficient in moving nutrients and waste across the membrane Information Overload – DNA not able to meet demands of cell Exchanging Materials – surface area to volume ratio Food and oxygen enter Waste leaves

Cell Growth, Division, and Reproduction Cell Division – To avoid size issues, the cell will divide into two daughter cells Cell division reduces the volume of a cell (increases SA/V ratio) This allows the daughter cells to efficiently exchange materials Before Cell Division – the cell replicates all of its DNA This solves the issue of information overload Each daughter cell receives one complete set of DNA

Cell Growth, Division, and Reproduction Cell Division and Reproduction Asexual Reproduction – genetically identical offspring from a single parent Examples: single-celled organisms Sexual Reproduction – Offspring inherit genetic information from each parent Examples: most animals and plants

Process of Cell Division What role do chromosomes play? Chromosomes make it possible to separate DNA precisely during cell division Chromosomes carry – Genetic information in packages called DNA Prokaryotic chromosomes – are circular and carry all of the cell’s genetic info Chromatin – Complex of chromosome and histone Nucleosomes – Bead-like structures made of coiled DNA and histones

Process of Cell Division Cell Cycle Main Events – the cell grows, prepares for division, and divides into daughter cells Prokaryotic Cell Cycle – Asexual reproduction Regular pattern of growth, replication, and division Eukaryotic Cell Cycle – Consists of four phases

Process of Cell Division Interphase – “in- between” periods of growth G1 phase – Growth Phase Cell Grows – mostly during this phase DNA is unchanged Makes new proteins and organelles Time – longest phase of Interphase (about 11 hrs) Intense growth and activity

Process of Cell Division Interphase S phase – DNA Replication DNA is replicated Time – about 8 hours At the end – twice as much DNA as it did at the beginning

Process of Cell Division Interphase G2 phase – Preparing for Cell Division Preparations – Final production of organelles Organelles – are replicated Time – about 4 hours Microtubules – start to form

Process of Cell Division M phase- Mitosis Two main steps Mitosis When nucleus – is divided in half Time – about an hour Each ends up – with a complete set of chromosomes (DNA) Cytokinesis – Division of the cell membrane and cytoplasm

The Cell Cycle As cells grow and divide they go through three distinct stages: Interphase Mitosis Cytokinesis

Interphase Longest stage of cell cycle Cell carries out all life activities Growth, cellular respiration, specialized functions for the cell type, etc. Also begin to prepare for cell division DNA is in long, thin strands called Chromatin

Cell Division Cell division occurs in two phases: Mitosis - the division of the nucleus Prophase Metaphase Anaphase Telophase Cytokinesis- the division of the rest of the cell

*Centrioles move to opposite ends Prophase Long strands of DNA condense into Chromosomes Nuclear membrane dissolves Centrioles move to opposite ends Spindle fibers begin to form Each chromosome has 2 identical strands called (Sister) Chromatids Sister chromatids are held together by the Centromere *Centrioles move to opposite ends

Metaphase Spindle fibers attach to centromere Chromosomes line up in the middle of the cell All chromosomes must be in line for mitosis to continue

Anaphase Centromere splits and spindle fibers pull sister chromatids apart Chromatids are now called “Chromosomes”

Telophase Daughter chromosomes start to decondense back into thinner strands of chromatin Nuclear membrane reforms

Cytokinesis Cells divide Two genetically identical daughter cells are formed Animal Cells In animal cells, the cell membrane is divided into two cells Known as the Cleavage Furrow Plant Cells Plant cells do not have centrioles In plant cells, a cell plate forms between the daughter cells and develops into a cell wall

Regulating the Cell Cycle How is the cell cycle regulated? Controlled by regulatory proteins Internal Regulators – allows the cell to proceed through mitosis when necessary External Regulators – tell the cell to speed up or slow down growth Growth Factors – stimulate growth and cell division Apoptosis – programmed cell death

Regulating the Cell Cycle Cancer How do cancer cells differ from other cells? they don’t respond to signals uncontrollable growth Cancer – body cells lose ability to control growth Tumor – mass of cells Benign Tumor – non- migrating tumor cells Malignant Tumor – migrating tumor cells

Regulating the Cell Cycle Cancer What causes cancer? defects in the genes that regulate cell growth and division Treatments: Surgery Radiation Hormone Therapy Chemotherapy Targeted Therapy