CELL GROWTH How big are cells Cells are

CELL GROWTH

How big are cells? • Cells are microscopic, too small to be seen by the naked eye. • Most human cells are 0. 01 -0. 03 mm. • But small is still relative!

QUESTIONS ? ? ? • When a living thing grows, what happens to its cells? • Does it get larger because: a. each cell increases in size? b. It produces more cells?

QUESTIONS • When a living thing grows, what happens to its cells? • Does it get larger because: a. each cell increases in size? b. It produces more cells!

Fertilization • When a male sex cell (sperm) and a female egg cell (ovum) fused, it became one cell (zygote). • So we started off as one cell.

How many • On average the human adult has about 100 trillion (100, 000, 000) cells. A new born baby? About 430 billion (430, 000, 000) cells.

Questions • Why do we have so many small cells? • What can’t we be just one big cell? • Is there an advantage to having many small cells? • Is there a disadvantage to having large cells?

CELL SIZE LAB (procedure) 1. 2. 3. 4. Cut 3 cubes 3*3, 2*2, 1*1 and place in cup. Add vinegar until completely submerged. Complete Table 1. After 10 minutes, remove agar cubes and blot dry with tissue paper. 5. Cut all 3 cubes in half and measure the distance in centimeters that the vinegar diffused into each cube. 6. Complete Table 2.

CELL CYCLE (con’t) 7. In Table 3 estimate the percent of diffusion into each cube. 8. Calculate the volume of the portion of each cube that has not changed color. Record your results in Data Table 3. 9. Calculate the extent of actual diffusion into each cube as a percent of the total volume.

Answer on back of Lab Sheet. 1. What did the different size cubes represent? 2. Which nutrients does the vinegar represent? 3. Look at Data Table 2. Make a statement about the relationship between cell size and the rate of diffusion. 4. Look at Data Table 1. Describe what happens to the surface area, the volume and the ratio as a cell grows larger? 5. Why is it more advantageous for cells to be smaller rather than larger? 6. Make a statement about the surface area/volume ratio (table 1. ) and the extent of diffusion (table 3. ).

Points to Remember • Small cells have a larger surface area to volume ratio. • Smaller cells are more efficient than larger cells. • Rate of diffusion does not change. • Smaller cells have a better extent of diffusion

CELL GROWTH AND DIVISON (Vocabulary) Mitosis – division of nucleus • • Cytokinesis – division of cytoplasm • Centromere – area where chromatids of chromosomes are attached • Interphase – period of cell cycle between cell divisions – G 1 – reproduction of organelles – S - chromosomes – G 2 – reproduction of centrioles • Cell Cycle – series of events as a cell grows and divides • Prophase – chromosomes become visible, centrioles separate, move towards poles of cell • • • Metaphase – chromosomes line up along the center of the cell Anaphase – chromosomes separate and move towards opposite poles Telophase – chromosomes disperse into a tangle of dense material Centriole – tiny structures that produce spindle fibers Spindle – help separate the chromosomes during cell division

Cell Division • Cell Division solves the problem of a cell growing to large. • (Cell Division – the process by which a cell divides into two new daughter cells)

Cell Cycle • Interphase: – G 1 Phase – S Phase – G 2 Phase • Mitosis (division of the nucleus) • Cytokinesis (division of the cytoplasm)

G 1 Phase • G 1 Phase is a period of activity in which cells do most of their growing. • During this phase cells increase in size and synthesize new proteins and organelles.

S Phase • Chromosomes are replicated and the synthesis of DNA molecules takes place. • Histones are also synthesized.

G 2 Phase • G 2 phase is normally the shortest of the three stages of interphase. • Centrioles copy themselves.

Mitosis • A type of cell division where the nucleus divides • Mitosis has 4 stages – Prophase – Metaphase – Anaphase – Telophase

Prophase • • Chromatin coils up into chromosomes Nuclear membrane disappears Nucleolus disappears Centrioles begin to move towards the poles

Metaphase • Chromosomes line up at the center of the cell. • Spindle Fibers connect to centromeres of Chromosomes • Centrioles move the poles of the cell

Anaphase • Sister chromatids separate and move apart

Telophase • Chromosomes uncoil and disperse • Nuclear Envelope begins to reform • Cytoplasm begins to pinch in half

Cytokinesis • Cytoplasm pinches in half and the two cells separate.

• Mitosis Video. • Different Organisms and their chromosome count.

Assessment • Turn to questions 1 -7 on page 257. • Answer them on a blank sheet of paper.

Arrange the 7 steps in Order • • Anaphase Metaphase Cytokinesis Interphase Telophase Late Prophase Early Prophase

QUESTION 1 • The number of chromosomes in a human cell is _______. A. B. C. D. 2 4 23 46

QUESTION 2 • Genetic information is transferred from parent to daughter cells through the _______. A. B. C. D. endoplasmic reticulum mitochondria nucleus centrioles

QUESTION 3 • The resting stage of the cell is known as the _______. A. B. C. D. anaphase prophase telophase interphase

QUESTION 4 • During which stage of mitosis do nucleoli reappear? A. B. C. D. Anaphase Early Prophase Late Prophase Telophase

QUESTION 5 • During which stage of mitosis do chromatids separate? A. B. C. D. Anaphase Prophase Interphase Telophase

QUESTION 6 • Which of the following is NOT correct? A. B. C. D. Mitosis is produces genetically identical cells. Cytokinesis is a part of mitosis Metaphase occurs before anaphase. All somatic cells are produced by mitosis.

CELL CYCLE REGULATION • Not all cells move through the cell cycle at the same rate: – Muscle and nerve cells do not divide at all once they have developed. – Skin, digestive tract and bone marrow cells grow and divide rapidly (every few hours). – Cells in a petri dish (page 250).

Cell Cycle Regulators • Hunt and Kirschner discovered cyclin, a protein what when injected into a nondividing cell made it divide (page 251). • Cell growth is regulated carefully. Uncontrolled cell growth is severe. Cancer is a disorder in which some of the body’s cells lose the ability to control growth. • Masses of cells called tumors develop.

MEIOSIS (pages 275 -277)

MEIOSIS Vocabulary • Meiosis - process by which the number of chromosomes is cut in half through the separation of homologous chromosomes. • Homologous chromosomes – chromosomes that each have a corresponding chromosome from each parent. • Diploid (2 N) – a cell that contains both sets of homologous chromosomes. • Haploid (N) – a cell that contains only a single set of chromosomes. • Tetrad – structure containing 4 chromosomes that forms during meiosis. • Crossing Over – process by which homologous chromosomes exchange portions of their chromatids during meiosis. • Gamete – specialized cell involved in reproduction (female gamete = egg/ovum, plural ova//male gamete = sperm) • Somatic cells – body cells. • Sexual Reproduction – process by which cells from two different parents unite to produce the first cell of a new organism. • Asexual Reproduction – process by which a single parent reproduces by itself.

Questions • How many chromosomes do human being have? • Can reproduction work by mitosis work? (draw diagram) • What do you think has to happen for every human being to maintain that number of chromosomes? • Chromosome number has to halved!

Meiosis Overview • • Cells produced are haploid Two divisions (Meiosis I & II) 8 Stages (P 1, M 1, A 1, T 1, P 2, M 2, A 2, T 2) Prophase 1: Tetrads (4 chromatids) form Prophase 1: Crossing over occurs Four daughter cells (gametes) produced Interphase does NOT occur between M 1 and M 2 • MEIOSIS VIDEO

What do you notice? • Down’s Syndrome or Trisomy 21.

Down’s Syndrome

Question 1 • Which cells are not formed during meiosis? A. B. C. D. somatic cells Gametes Sex cells Sperm cells

Question 2 • Which is part of meiosis but not mitosis? A. B. C. D. Cell division Duplication of chromosomes Reduction of chromosome number Production of new cells

Meiosis, 8 stages you can tell, Meiosis, produce 4 daughter cells, Meiosis, just before the cell splits, Meiosis, half the chromosomes is what it gets. (Repeat twice) • •

Verse If we want to grow or cells need repair, Don’t fear, MITOSIS will be there, But when we need reproductive cells, MEIOSIS is the process that does it well.