Cellular Growth Ch 9.1

Surface Area To volume Ratio Surface Area to volume ratio limits size As surface Area Doubles the Volume increases by 4 times! Makes large Cells less efficient

Why do cells need to be efficient? Transportation: Diffusion over large distances is inefficient and slow Small size helps maintain transportation of substances

Why do cells need to be efficient Communication: Small cells are able to communicate cellular instructions better than large cells. Signal molecules move throughout the cell

The Cell cycle A cycle of Cells growing and then dividing When a cell grows too large it divides into two cells. Division is how cells reproduce

Steps of Cell cycle Interphase – Cell Grows, carries out cellular functions and replicates DNA. Longest Step of cell cycle Mitosis – Nucleus and DNA is divided Cytokinesis – Cytoplasm is divided creating 2 daughter cells

Interphase The first stage of interphase is G 1 The Cell grows and functions normally.

Interphase The second stage is S The Cell copies it’s DNA.

Interphase The last stage of interphase is G 2 The Cell prepares for division

Copy the questions to your notes! What limits Cell size? 2. What are the three steps of the cell cycle 3. Which step is the longest? 4. What are the three phases of Interphase? Surface area to volume ratio Interphase, Mitosis, Cytokinesis Interphase G1, S, G2

Mitosis and Cytokinesis Chapter 9.2

Mitosis Division of the nucleus resulting in 2 identical daughter cells. Usually followed by cytokinesis the division of the cytoplasm.

Genetic Material Chromatin – The DNA in the nucleus (looks stringy) Chromosome – A single DNA molecule, visible as a bar-like structure during cell division. (human = 46 chromosomes)

Four stages of Mitosis (PMAT) Prophase Metaphase Anaphase Telophase

Prophase Chromatin condenses to chromosomes Nuclear Membrane and nucleolus disappear Centrioles migrate to poles Spindles form

Metaphase Spindles attach to chromosomes Chromosomes line up along the middle of the cell

Anaphase Sister chromatids separate Chromosomes move toward the poles

Telophase Chromosomes arrive at poles New nuclear membrane begins to form Spindles disassemble

Cytokinesis Animals – microfilaments wrap around cytoplasm and pinch it to separate. Plant – a new structure called a cell plate forms to divide the two cells.

Copy the question to your notes! 1. How many chromosomes do humans have? 2. Before Chromosomes condense during mitosis they are stringy and called _______________. 3. What are the four stages of mitosis? 4. What happens after mitosis is finished? 46 Chromatin Prophase, Metaphase,anaphase,Telophase cytokinesis

Normal Cell cycle The cycle has built in checkpoints that monitor the cycle and can stop it if something goes wrong.

Abnormal Cell cycle: Cancer Cancer is uncontrolled cell growth and division Cancer cells can crowd out normal cells and kill an organism. Cancer cells do not grow like they should.

Causes of Cancer Genetics Changes during cell cycle regulation are due to DNA mutation Inherited genes Genes getting old Environmental effects Carcinogens cause cancer Examples: Tobacco, Ultraviolet radiation

Apoptosis Apoptosis is programmed cell death Cells shrink and shrivel in a controlled way.

Stem cells Unspecialized cells that can develop into specialized cells under the right conditions.

Copy the questions to your notes! What is built in to monitor the cell cycle? Uncontrolled cell growth is called ____________. Programmed cell death is called ____________. These cell are unspecialized and can turn into specialized cells in the right environment. Check points Cancer Apoptosis Stem cells