Cell Growth and Reproduction

Why cells are small Diffusion limits cell size Diffusion is fast and efficient over short distances, it becomes slow and inefficient over larger distances. Small cell = good diffusion Big cell = bad diffusion

DNA limits the cell size. The DNA tells the cell which proteins to be made. There production takes time to make. Not enough protein the cell will die.

Bigger cells need more protein than smaller cells. Bigger cells need more supplies than smaller cells.

Surface area to volume ratio 1mm x 1mm x 1mm surface area = 6mm 2 volume = 1mm 3

Double the cell size 2mm x 2mm x 2mm = surface area = 24 mm 2 volume = 8 mm 3

Surface Area 6mm 2 to 24mm 2 When surface area is doubled surface area increases 4 times.

Volume 1mm 3 to 8mm 3 when cell size is doubled volume increases 8 times.

Problem-Solving Lab 8-1 Do the problem solving lab on page 209.

Cell Reproduction All cells come from preexisting cells. Cell division is the process which new cells are produced from preexisting cells. Cell division results in two identical cells.

Chromosomes Scientists noticed that just before a cell divided several short stringy things appeared inside the nucleus. They vanished just after the cell divided.

It was discovered that chromosomes were tightly coiled (packed) strands of chromatin (DNA). This was the genetic material of the cell getting ready for the great divide (cell division)

DNA = Genetic code of cell Chromatin = long strand of DNA (uncoiled) Chromosome = Tightly coiled strand of DNA

The Cell Cycle Cells follow an orderly pattern called the cell cycle. The cell cycle is the sequence of growth and division of a cell.

Phases of the Cell Cycle Interphase –G1 phase –S phase –G2 phase –Mitosis

Interphase G1 phase - Rapid growth and metabolic activity S phase - DNA synthesis and replication G2 phase - Centrioles replicate cell preps for division.

Mitosis During mitosis a cell actually divides. There are 4 phases of mitosis Prophase Metaphase Anaphase Telophase

Prophase Chromatin coils forms chromosome. Chromosome is 2 identical chromatin (sister chromatids) hooked together by a centromere. Nucleus disappears

Centrioles begin to migrate to the opposite ends of the cell. Spindle forms between the centrioles.

Metaphase Spindle fibers emerge from the spindle and attach to the centromeres. Chromosomes line up in the middle of the cell.

Spindle fibers attach from the centromeres to the centrioles.

Anaphase Centromeres split Sister chromatids separate Chromatids are pulled apart toward the centrioles.

Telophase Chromatids reach opposite sides of the cell. Chromosomes unwind Spindle fibers breakdown Nucleus (two) reform

A new membrane grows between the two nuclei. Cytokinesis - cytoplasm divides producing two new cells.

END RESULT of MITOSIS 2 identical daughter cells from one parent cell.

Plants - Cells do not separate but stay together. Animals - Cells separate.

ASSIGNMENT Problem Solving Lab 8.2 Page 210.

The big overview Cells make, tissues Tissues make up Organs Organs make up Organ systems organ systems make up Organisms.

Control of the Cell Cycle Enzymes - Special proteins used by the cell to control the rate of chemical reactions. Enzymes monitor a cell’s progress from phase to phase during the cell cycle.

Occasionally, cells lose control of the cell cycle. Cancer is one result of uncontrolled cell division.

Failure to produce enzymes, overproduction of enzymes or production of enzymes at the wrong time result in uncontrolled cell division.

Enzyme production is controlled by genes located on the chromosomes. A gene is a segment of DNA that controls the production of a protein.

Cancerous cells form masses of tissue called tumors that deprive normal cells of nutrients. In later stages, cancer cells enter the circulatory system and spread.

Cancer is the second leading cause of death in the United States. Do the Problem solving lab page 218.

CAUSES OF CANCER Both genetic and environmental factors are involved in causing cancer.

Environmental Factors Where you live. Cigarette smoke Air and water pollution Exposure to UV radiation Diets high in Fat

Cancer Prevention Diets high in fiber Low in fat Fruits and Vegetables and grains Vitamins A, C, E and calcium. Carotenoids

Daily Exercise Avoid using tobacco