Cell Growth and Reproduction Chapter 5

Limits to Cell Size Cell is too small: Cell is too small: Not enough room for organelles and molecules Not enough room for organelles and molecules As a cell grows, its volume increases much faster than its surface area. As a cell grows, its volume increases much faster than its surface area. Cell is too big: Cell is too big: Diffusion of molecules will be too slow. Diffusion of molecules will be too slow.

Why can’t most organisms be just one giant cell? Diffusion limits cell size Diffusion limits cell size DNA limits cell size DNA limits cell size Surface area-to-volume ratio Surface area-to-volume ratio As cell’s size increases, its volume increases much faster than its surface area As cell’s size increases, its volume increases much faster than its surface area

Cell Reproduction Chromosomes: 1. Structures that contain DNA 2. Dark when stained. 3. Carriers of genetic material (passed from generation to generation.) 4. Typically exist as chromatin – (long strands of DNA wrapped around proteins.)

The Cell Cycle Occurs in Eukaryotic Cells Occurs in Eukaryotic Cells Regular pattern of: Regular pattern of: Growth Growth DNA duplication DNA duplication cell division cell division 4 Stages in the cell cycle: 4 Stages in the cell cycle: Gap 1 (G 1 ), Synthesis, Gap 2 (G 2 ), Mitosis Enzymes control the transfer through the stages Enzymes control the transfer through the stages

Gap 1 (G 1 ) First Stage First Stage Cell carries out normal functions Cell carries out normal functions Cell increases in size Cell increases in size Organelles increase in number Organelles increase in number

Synthesis Second Stage Second Stage Synthesis = “the combining of parts to make a whole” Synthesis = “the combining of parts to make a whole” Cell makes a copy of its DNA Cell makes a copy of its DNA

Gap 2 (G 2 ) Third Stage Third Stage Similar to G 1 phase Similar to G 1 phase Includes a critical checkpoint … the cell will only reproduce if everything is in order. Includes a critical checkpoint … the cell will only reproduce if everything is in order.

The Cell Cycle The sequence of GROWTH and DIVISION of a cell: The sequence of GROWTH and DIVISION of a cell: Interphase – Growth stage of cell cycle Interphase – Growth stage of cell cycle Mitosis – Division stage of cell cycle. Mitosis – Division stage of cell cycle. Prophase Prophase Metaphase Metaphase Anaphase Anaphase Telophase Telophase Cytokinesis – process in which cell’s cytoplasm divides Cytokinesis – process in which cell’s cytoplasm divides

Interphase 1. Precedes Mitosis 2. Includes G1, Synthesis, and G2 stages 3. Most of a cell’s life is spent in this growth stage 4. Chromosomes are duplicated in preparation for cell division

Prophase 1. First and longest stage of Mitosis 2. Chromatin uncoils to form visible chromosomes 3. Chromosomes composed of two halves called sister chromatids 4. Sister chromatids are held together by a centromere. 5. Nuclear Envelope disintegrates (disappears) 6. Centrioles and spindles help in chromatid separation

PROPHASE

Metaphase 1. 2 nd phase of mitosis 2. Chromosomes move to the equator 3. Each sister chromatid is attached to its own spindle fiber 4. Spindle fibers are attached to centromere

METAPHASE

Anaphase 1. 3 rd phase of mitosis 2. Centromeres are split 3. Sister Chromatids are pulled apart

ANAPHASE

Telophase 1. 4 th and Final stage of Mitosis 2. Chromatids reach opposite poles of the cell 3. Two distinct daughter cells are formed 4. Processes of prophase are reversed

TELOPHASE

Results of Mitosis Creates two new cells from original: Creates two new cells from original: Chromosome sets are identical to parent cell. Chromosome sets are identical to parent cell. Guarantees genetic continuity Guarantees genetic continuity Creates tissues, organs, and organ systems Creates tissues, organs, and organ systems

Interphase MetaphaseAnaphase Telephase/ Daughter Cells Prophase Mitosis of an onion cell

Mitosis of a White Fish Blastula Cell

What is Cancer 2 nd leading cause of death in U.S. 2 nd leading cause of death in U.S. ½ of men and 1/3 of women develop it ½ of men and 1/3 of women develop it 200 different types 200 different types Risk can be reduced by lifestyle changes Risk can be reduced by lifestyle changes

Normal Cell Organization Groups of cells form organs which produce functions. Groups of cells form organs which produce functions. Early in life, cells divide frequently Early in life, cells divide frequently Later in life, cells only grow and divide to replace old cells or repair injuries Later in life, cells only grow and divide to replace old cells or repair injuries

Cancer Cell Organization Abnormal Cells (mutated DNA or don’t perform proper function) Abnormal Cells (mutated DNA or don’t perform proper function) Inherit damaged DNA from Parents Inherit damaged DNA from Parents Damaged by exposure to something (sunlight, smoking, etc.) Damaged by exposure to something (sunlight, smoking, etc.) Out of control cell multiplication; forms mass of cells (tumors) Out of control cell multiplication; forms mass of cells (tumors)