Cell Growth and Division Biology Unit 4 Ms. Lew

Vocabulary (p. 90-91) Cell Cycle Chromatin Chromosome DNA overload Interphase Sister Chromatid Spindle Fiber

Key Concept: Most living things grow by __________________________. On average, the cells of an adult animal are ______________ the cells of a young animal. Making more cells No larger than

List two reasons why cells divide rather than continue to grow larger: DNA Overload __________________________________ Exchanging Materials

DNA Overload: DNA overload is when the DNA has too many tasks to do (such as making proteins) and not enough DNA to get the job done efficiently. To prevent DNA overload cells stay small to limit a cells work load.

Materials exchange becomes more difficult in large cells: Materials move into and out of cells Cells need to take in materials such as oxygen, water and glucose. Cells need to get rid of materials such as carbon dioxide, salts, other waste. Large cells lose efficiency in this process – surface area and volume do NOT increase at the same rate.

How do you determine the surface area of a cube? Length x Width x 6

How do you determine the volume of a cube? Length x Width x Height

How do you determine the ratio of surface area to volume? Surface Area / Volume

Why is the ratio of surface area to volume in a cell important? This ratio is what determines HOW MANY and HOW FAST substances can enter the cell. As a cell grows, its SA/V ratio DECREASES, and the cell can no longer be supplied enough nutrients, and stops growing

Door analogy More doors, less time it takes for people to get out of classroom.

Ratio of Surface Area to Volume Find the surface area, volume and surface area to volume ratio of the following cube-shaped cells: 2cm 4cm 6cm Surface Area Volume Ratio of Surface Area to Volume 24 cm2 96 cm2 216 cm2 8 cm3 64 cm3 216 cm3 3:1 1.5:1 1:1

Vocabulary (p. 90-91) Must find definitions on your own by Notebook check #2 Cell Cycle Chromatin Chromosome DNA overload Interphase Sister Chromatid Spindle Fiber Interphase Sister Chromatid Spindle Fiber

What is the cell cycle? During the cell cycle, a “parent” cell grows and divides to form 2 “daughter” cells. The cycle has three main stages Interphase Mitosis Cytokinesis

Remember the two reasons why cells divide rather than continue to grow larger: DNA Overload __________________________________ Exchanging Materials

The Cell Cycle Animation

G1 M S G2

Interphase – G1 , S & G2 During Interphase cells: Grow to mature size Mitochondria and chloroplasts are duplicated Replicate (copy) DNA Each cell needs instructions Prepare for cell division Cell grows Most of a cells life is spent in Interphase.

Chromosomes Are made of DNA Each chromosome consists of sister chromatids attached at a centromere Each sister chromatid is an exact copy

Mitosis – M phase P M A T The cells nucleus divides into two nuclei There are four phases Prophase Metaphase Anaphase Telophase P M A T

Animal Cell Mitosis- Video

Prophase 1st stage of Mitosis Chromatin condenses into chromosomes Centrioles separate and a spindle fiber begins to form. Nuclear membrane breaks down

Prophase

Metaphase 2nd Phase of Mitosis Chromosomes line up in the middle of the cell. Each chromosome is connected to a spindle fiber.

Metaphase

Anaphase 3rd Phase of Mitosis The sister chromatids separate at the centromere and move to opposite ends of the cell.

Anaphase

Telophase 4th Stage of Mitosis Chromosomes gather at opposite ends of the cells and lose their shapes (return to chromatin form) Two new nuclear membranes form, one for each cell.

Telophase

Stage 3: Cytokinesis The cytoplasm pinches in half. Each daughter cell has an identical set of duplicate chromosomes

Cytokinesis

Overview sim http://www.sumanasinc.com/webcontent/animations/content/mitosis.html

Plant cell mitosis https://www.youtube.com/watch?v=aDAw2Zg4IgE

And Another one… https://www.youtube.com/watch?v=KzBoIAMVUSY