 A eukaryote cell is very small with an average size of 10 microns across.  1 micron = 1/1,000,000 of a meter or 1 x m  1 micron = 1/1000 of a millimeter or 1 x mm

 A human is made of about 10 trillion cells.  But the number of prokaryote cells both on and in one human is more than that!!!  Prokaryote cells are much smaller than eukaryote cells.

Each fertilized cell DIVIDES and Divides and DIVIDES and DIVIDES.

Development of Sea UrchinSea Urchin  Early development in a sea urchin ( Lytechinus pictus) embryo illustrates how a single egg develops into a hollow blastula.  Elapsed time about 2 hours. ction

With your group:  Fold your boxes  Measure the volume  Complete worksheet

 Cells are small to maximize their surface area  A high surface area is critical to the rapid diffusion of material into and out of the cell.

 Rapid diffusion of glucose, oxygen, carbon dioxide and other molecules is necessary for the maintenance of cell function.

 A cell grows to its optimal size and then it divides in half.  Each half will form a new cell that grows until it reaches its optimal size, and then it too will divide in half.

 Large cells To Do: Use white board to draw/label cell’s dimensions  With your group design a cell that has a volume of 36 cm 3 AND the largest possible surface area.  Use whole number for each dimension!  Consider: How do you maximize surface area?

 Another type of large cell is an egg.  A bird’s egg is one large cell. The yolk is a food source for the growing embryo.  How is it possible for a bird’s egg to function when it is so large? Food is already present—diffusion isn’t needed to meet the nutritional needs of cell

 Small cells optimize the movement of material in and out of the cell  DNA in the nucleus of the cell controls the activity of the cell. If a cell increased in size, its activity would increase.  The quantity of DNA in the cell would not be able to control all the activities of the larger cell.

 1 parent cell divides into 2 daughter cells. This decreases volume and increases surface area of each cell.  When the cell divides in half, the material must be divided evenly

 Cell division occurs through binary fission= reproduction (in prokaryotes)  All genetic material (DNA) in the cell is found on one chromosome floating in the cytoplasm.

 Cell division begins with replication (doubling) of the chromosome.  The two chromosomes move to opposite ends of the cell.  Cell splits apart into two daughter cells--each containing one chromosome and half of the cytoplasm  Each daughter cell is genetically identical*identical*

 C hromosome = a structure in eukaryotes and prokaryotes made of a long strand of a DNA molecule bonded to histones.  Histones are proteins that provide structure for the chromosome Histones DNA

 Each eukaryotic cell contains a nucleus with chromosomes.  Each species has a characteristic number of chromosomes. Humans have 46 chromosomes in the nucleus of each of their cells (23 chromosomes from each parent)

 Eukaryote cells are much more complex than prokaryote cells and the cell cycle is much more complex.  Four phases of cell cycle. The cell cycle represents the entire lifetime of a single cell  M phase (mitotic phase)  G 1 phase (gap 1)  S phase (synthesis)  G 2 phase (gap 2) INTERPHASE

 Longest part of cell cycle (90%). This is when the cell is “doing its job”.  Divided into 3 phases  G 1 phase - (gap 1) - Period of cell growth, development and repair. Cell increases in size; proteins and organelles are produced.

 S phase - (synthesis) – Preparation for cell division.  Occurs in nucleus: All genetic material is doubled.  The genetic material before mitosis begins is called chromatin. Chromatin is made of long strands of DNA wrapped around histones. This is what the nucleus of the cell looks like during interphase This is what the nucleus of the cell looks like at the start of cell division

 G 2 phase - (gap 2) -- Organelles (example: centrioles) and molecules specifically required for cell division are produced.

Interphase

 Mitotic Phase – The division of the cell Includes  Mitosis (4 phases) = division of the nucleus AND  Cytokinesis = division of the cytoplasm

What happens?  Chromatin in the nucleus comes together and forms chromosomes  Each chromosome is made up of two identical copies (sister chromatids), which are attached together in the middle (centromere). Cell in Prophase

 Centrioles  Four found in the cytoplasm of each animal cell  Move to opposite ends of the cell (2 on each side)  Spindles  Fan-like structures made of microtubules grow out from the centrioles towards the center of the cell  The nucleolus disappears.  The nuclear envelope breaks down*.down*. Centrioles Sister Chromatids

 Quick vocabulary check! Centromere vs. sister chromatids DNA vs. histone. Macromolecules Chromosomes vs. chromatin Cytokinesis vs. Mitosis InterphaseGap 1 and Gap 2 and Synthesis Mitotic Phase vs. Mitosis

 Chromatids line up at the center of the cell.  Each chromatid is attached to a spindle fiber at the centromere* centromere*

 Anaphase  Centromeres separate.  Each sister chromatid becomes a separate chromosome.  Spindles contract -- causing chromosomes to more towards opposite ends of the cell near the poles of the spindles*. spindles*.

 Telophase  Chromosome gathers at either end of the cell and begin to lose their shape. They turn back into ________________  A nuclear envelope forms around each group of chromosomes.  Nucleolus forms in each nucleus.  Spindle fibers break apart. chromatin

 Division of cytoplasm  Occurs at same time as telophase  Cell membrane pinched into two parts with one nucleus and an equal number of organelles in each part.  New cell membrane forms around each cell*.each cell*

 In plants--Spindle fibers form during prophase BUT there are no centrioles.  In plants - Cytoplasm  Does NOT pinch together  Instead, a cell plate forms which divides the cell in half.  Each half contains a nucleus and equal amounts of organelles and cytoplasm.  New cell wall forms in cell plate

 Unicellular organisms = reproduction  Multicellular organisms = growth, development and repair

 Create Mitosis Flipbook using directions OR  Mitosis Song OR  Mitosis Dance OR  Other

 Lab: Observation of cells undergoing mitosis within an onion root

 How do cells "know" when to begin each phase of the process of the cell cycle?  Normal growth, development and maintenance are dependent on the proper control of the timing and rate of cell division.

 Cyclin – a family of regulatory proteins found in all eukaryotes that drive the cell through the different stages of the cell cycle. Concentration

 3 check-points during cell cycle - if message is received to "go-ahead" the cell cycle continues. If no message is received the cell cycle stops-- division does not occur.

 Experiment: Two cells in Interphase were injected with cytoplasm. Cytoplasm from cell in interphase Cytoplasm from cell in mitotic phase Cell enters mitosisCell remains in interphase What happens to the cells?

 Especially important in embryonic development and wound healing.  Growth factors - Nutrients and proteins outside of cell. Cause cell cycle to speed up or slow down.

 Experiment  Cells placed in Petri dish  Cells grow and divide until they fill the entire plate. When the cells touch each other the rate of division slows down  Cells are removed from dish.  They grow and divide until they touch each other and then the rate of division slows.

 The growth pattern seen in the experiment is what occurs during the healing of a wound.  Cell division increases when the cells are separated  Once the cells have rejoined, cell division decreases.  The controls on cell division can be turned on and off!

 Cancer is a family of diseases. Some are relatively easy to cure, others are fatal.  All types of cancer involve a break-down in the cell cycle control system.  All cancer cells divide at a rapid rate indefinitely without stopping.

 A large number of cancerous cells have a defect in one of their internal regulators  gene p53.  Gene p53 is a tumor suppressor and if it does not function, cancer is the result*.cancer is the result

 Usually, a cell that does not respond to the cell cycle controls is destroyed.  If not, a tumor forms = a mass of abnormal cells developing within a tissue. Cells are disorganized and grow irregularly.

 Benign tumors - remain at original site, are non-invasive and can be surgically removed  Malignant tumors - cause cancer--cells invade and disrupt functioning of organs. These cells usually contain an abnormal number of chromosomes.  Metastases - Cancer cells (depending on type) may be invasive. Cells from a tumor may break off and spread through the body in blood cells and invade other organs*.organs*.

 In USA: 1 of 4 deaths is caused by cancer.  What causes cancer cells to form?  Smoking tobacco  Exposure to radiation  Certain viruses  Environmental factors  Genetic factors

 First step (usually) is surgical removal of tumor.  If all cancer cells are removed and the affected organ is not damaged the person is considered cured.  Other treatments:  Radiation therapy  Chemotherapy Used separately or together

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