The Cell Cycle Growth reproduction and functions Cell

The Cell Cycle Growth, reproduction and functions

Cell Cycle has Four Main Stages • • Gap 1 Synthesis Gap 2 Mitosis

What is Mitosis? • Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei • Occurs exclusively in Eurkaryotic cells

Interphase Parent cell centrioles spindle fibers centrosome nucleus with DNA

Pnuemonic for Mitosis People may answer telephones • Prophase • Metaphase • Anaphase • Telophase

It’s all Greek to Me The word ‘phase’ = appearance • Inter = between • Pro = before • Meta = after • Ana = back • Telo = end What do you think the prefixes used are referring to? Appearance of chromosomes.

Cytokinesis • The division of the cytoplasm and the plasma membrane following the division of the nucleus resulting into two cells, each having its own nucleus and cytoplasm surrounded by a plasma membrane.

Don’t confuse the Two • Mitosis—division of cell nucleus • Cytokinesis—division of cell cytoplasm results in two cells each of which contain s one of the nuclei from mitosis Parent cell mitosis cytokinesis daughter cells

CELL REPRODUCTION STEPS OF INTERPHASE: • G 1 (Growth 1) phase: --cell grows and is metabolically active --RNA and new proteins are made --energy is needed for these things to occur • S (Synthesis) phase --DNA content of cell doubles --genetic info is copied exactly

CELL REPRODUCTION STEPS OF INTERPHASE: • G 2 (Growth 2) phase: --another phase of growth and metabolism --RNA, proteins, etc are synthesized in smaller amounts --A substance is made that TRIGGERS the start of cell division

CELL REPRODUCTION STAGES OF MITOSIS • PROPHASE: --Chromatin condenses down into chromosomes --NUCLEAR ENVELOPE disappears --Spindle apparatus forms and spindle fibers attach to chromosomes

CELL REPRODUCTION STAGES OF MITOSIS • METAPHASE: --Chromosomes move to the center of the cell • ANAPHASE: --Chromosome strands pulled toward poles

CELL REPRODUCTION STAGES OF MITOSIS • TELOPHASE: --Chromosomes gather at poles --NUCLEAR ENVELOPE reappears --Organelles segregate --Cytokinesis, division of cytoplasm occurs

Cells divide at different rates • It’s linked to the body’s need for those cells. • In humans—the S, G 2 and M stages take approximately 12 hours

Question? • Do you think a skin cell would have a long or short G 1 stage? • A short G 1 because skin cells undergo a lot of wear and tear so they are replaced quicker.

Cell size is limited • What formula is used to calculate the surface area of the cell? Length x width x number of sides • What formula is used to calculate the volume of a cell? Length x width x height Rememer: the surface area of a cube increases by the length squared and its volume increases by length cubed.

5. 2 Mitosis and Cytokinesis DNA is made of four different subunits called nucleotides. What would you do if you had to put a lot of clothes into a small suitcase? Compress the clothes If you were sharing the suitcase with your twin sister or brother, what would you need to do? Compress the clothes, and later separate them DNA needs to be both condensed and separated for a cell to divide.

Chromosomes organized structure of DNA and protein • 1 -Chromatid-one of two identical parts of chromosome after S phase • 2 -Centromere-point where two chromatids touch and microtubles attach • 3 -Short arm • 4 -Long arm • Telomeres-repeating nucleotides that do not form genes; prevent the ends of chromosomes from accidentally attach to one another and help prevent the loss of genes.

Histones • At almost all times during the cell cycle, chromosomes are associated with histones • Act as spools with which DNA winds forming chromatin • Major role in gene regulation DNA double helix DNA and histo nes Chro matin Supercoil ed DNA

Chromatin “loose” combination of DNA and proteins that makes up chromosomes—DNA is organized in the cell by wrapping around histones at regular intervals Interactions between parts of the histones further compact the DNA

Supercoiled DNA • Chromatin coils more and more tightly around organized proteins

Infer • Overall, DNA has a negative charge. Look at the histones figure on page 139 of your book. • What type of overall charge do you think they have? • Positive; negative and positive charges attract. If the histones were negatively charged, they would repel DNA

Apply • What is the relationship between a molecule of DNA and a chromosome? • A chromosome is made of one continuous DNA molecule. • DNA is organized in the cell by wrapping around histones at regular intervals • Remember: two spiraling strands of DNA double helix represent a single molecule.

5. 3 Regulation of the Cell Cycle • External factors --physical and chemical signals Example of physical factor: cell-to-cell contact

• Example of chemical factor: Growth factor Epidermal growth factor Nerve growth factor

Internal Factors • Kinases—(to move) enzyme that transfers a phosphate group from one molecule to a specific target molecule • Cyclins-group of proteins that are rapidly made and destroyed at certain points in the cell cycle. These factors help a cell advance to different stages of the cell cycle.

Apoptosis • Programmed cell death Human Example: cells between the webbed digits in human embryo die off resulting in unwebbed fingers and toes Plant example: deciduous tree leaves dropping off in fall

Cell division is uncontrolled in cancer • Bladder Cancer cells dividing Breast cancer cell Skin Cancer Cells Leukema

Benign vs Malignant Tumors

Metastasize • “break away, ” “leak, ” or “spill” from primary tumor and enter lymph system and blood vessels; circulate and then settle into new tissue to grow • Pancreatic cancer cells all over parts of liver

Skin Cancer

Cancer Treatment • Standard treatment involves both ionized radiation and chemotherapy • It works by damaging a cell’s DNA so much that the cell cannot divide.

5. 4 Asexual Reproduction • Most prokaryotes reproduce through binary fission (asexual reproduction of a single-celled organism by division into roughly equal parts). • parent cell • DNA duplication • cell begins to divide • daughter cells

Binary Fission

Advantages/Disadvantages of Asexual Reproduction Advantages: • More efficient • Produces a genetically identical offspring that is well suited to their environment • Don’t need to locate a mate (which uses energy) Disadvantages: Entire populations can die off if changes to environment occur– no diversity

Eukaryotes • Can reproduce asexually through mitosis Examples: Stem cutting for new plants New arm on sea star

Doing it Both Ways • Sea Anemone asexually--divides in half, by breaking off small pieces from its base or by budding sexually—by producing eggs and sperm

5. 5 Multicellular Life • What are some of the different types of cells in your hand? • Those making up skin, hair, fingernails, muscle, bone, blood, nerves • Are the cells in the trunk of your body any different? • Similar types of cells, but in addition, many more associated with internal organs.

Interactions among cell types • Tissues • Organ Systems

Question? • Suppose your family goes out of town and forgets to ask your neighbor to water the plants. Do you think the plants’ stomata will be open or closed? • Because the plants are not receiving water, they need to conserve it. The stomata will mostly likely be closed.

Cell • Vessel elements are tube-shaped cells

Tissue Cell • Vessel elements and tracheids form xylem

Organ • Xylem and other tissues form roots that absorb water and nutrients

Plant System

Cell Differentiation • Process by which unspecialized cells develop into their mature forms and functions.

Stem Cells repair system for body Unique type of body cell that have the ability to: 1) divide and renew themselves for long periods of time 2) remian undifferentiated in form 3) develop into a variety of specialized cell types

Stem Cell Classification

Mitosis vs Meiosis • Show clip http: //www. pbs. org/wgbh/nova/baby/divi_fl ash. html