10-1 Cell Growth Growth and Development!!
Definitions • Histones • Telomeres • Somatic cells • Chromatin • Chromosomes • Centromeres • Spindle fibers
Parts of a Chromosome • Chromosome: Long threads of DNA that consist of genes. • Humans have 46 chromosomes • Histones: proteins DNA wraps around. Makes it condensed!!! • Chromatin: Loose DNA when it is not condensed. DNA only condenses during mitosis and meiosis.
Chromatin - A complex of DNA and proteins in the cell nucleus that condenses to form chromosomes during cell division(loose DNA). • Chromosomes – Condensed Chromatin(X) • They are the same stuff, just in different forms • Centromeres: Center point where chromatids are attached. • Spindle Fibers - Fibers that pull part the chromosomes during mitosis.
Parts of the Chromosomes • Telomere: DNA molecules at the end of the chromosomes that do not code for genes. They keep the DNA from unraveling. • Chromatid:One half og the duplicated chromosome. • Centromere: Each sister chromatid is held together at the centromere. • ALL OF THIS IS FORMED AFTER REPLICATION!!!
Some Definitions • Histones: proteins that DNA will wrap around. This helps the DNA to fit. • Telomeres: End of DNA molecules to prevent them from attaching to each other. They do not contain genes. • Somatic Cells – body cells • Produced through mitosis • Has 46 chromosomes (23 pairs)
Chromatin Chromosomes Chromatin condenses in chomosomes before mitosis begins
When Do New Cells Need to Form? • A. Growth - More cells • B. Maintenance (repair and replacement)--> intestinal lining/RBC’s) • C. Asexual reproduction • D. Formation of sex cells (Meiosis)
Problem with Being Too Big!! • The volume gets too big for the surface area. • The cell membrane cannot control all the movement in and out when the volume is too large. • Your cells cannot too large either. The surface area must be in the correct ratio of the volume. • Neurons are very long and skinny so that ration is correct.
2. TOO BIG!: Cell membrane cannot control all movements of materials • The larger a cell grows the more trouble it has… • moving enough nutrients in • Moving all the waste materials out
3rd Problem - Too Big 3. DNA overload • Your DNA controls all activities in the cell. When the cell gets too big then the DNA cannot control all activites.
Radius 1cm S.A. = _____ V = ______ Ratio SA:V = ___ Radius 1cm S.A. = __13cm2___ V = __4cm3____ Ratio SA:V = _13:4 or 3.25:1__ Radius 2cm S.A. = ___50cm2__ V = __33cm3____ Ratio SA:V = 50:33_or 1.51:1 Radius 3cm S.A. = _____ V = ______ Ratio SA:V = ___ Radius 3cm S.A. = __113cm2_ V = ___113cm3___ Ratio SA:V = _113:113 or 1:1__ S.A. = 4 (pi) r 2 • As the spheres get larger what happens to the SA:V ratio?
Cell Cycle • Life Cycle of the cell! Most of the time your cells are growing. Divide after the cell has gotten too big!
Cell Cycle – life of a cell • The life of a cell. It has a pattern of cell growth, DNA replication, and cell division. Results in two new daughter cells.
The Cell Cycle • The sequence of growth and division of a cell. • 95% of cell cycle in interphase(growth) • 5% of cell cycle in mitosis(division)
3 Main Events of a Cell Cycle 1. Interphase • G1 - growth • S – DNA replication • G2 – growth and prepare for division 2. Mitosis Phase – nucleus dividing • Prophase • Metaphase • Anaphase • Telophase 3. Cytokinesis – cell division
The Cell Cycle - series of events that cells go through as they grow and divide • The cell cycle is divided into two halfs • Interphase - period of the cell cycle between cell divisions • Mitosis phase and cytokinesis – period of time when mitosis and cell division occurs
Parts of Interphase G1 Phase(growth) Cell grows Synthesize new proteins and organelles Doing their jobs Longest phase of cell cycle
S Phase S Phase(synthesis) Chromosomes(DNA) are replicated Key proteins associated with replication are made (centromeres
Gap 2 Phase G2 Phase(growth) Shortest of the 3 phases of interphase Organelles and molecules for cell division are produced (centrioles) Check-up phase before mitosis
Cell Cycle • http://www.cellsalive.com/mitosis.htm • http://www.johnkyrk.com/mitosis.html
Parts of Interphase • G1 Phase(growth) • Cell grows • Synthesize new proteins and organelles • Doing their jobs • Longest phase of cell cycle
S Phase • S Phase(synthesis) • Chromosomes(DNA) are replicated • Key proteins associated with replication are made (centromeres
Gap 2 Phase • G2 Phase(growth) • Shortest of the 3 phases of interphase • Organelles and molecules for cell division are produced (centrioles) • Check-up phase before mitosis
G - 0 Stage This is a stage of interphase that SOME cells enter. Cells such as nerve and white blood do not divide often so they enter this stage of rest.
Animated Cycle http://www.cellsalive.com/cell_cycle.htm
What stops cell from growing? • Proximity to neighbor cells. • Cells in a petri dish will continue to grow until they come into contact with other cells. • Similarily, skin around a wound After a cell has quit growing, it is time to divide!!! Mitosis
Mitosis Division of the nucleus. Followed by cytokinesis!!! The daughter cells are identical to one another and to the original parent cell.
Mitosis • Prophase • Metaphase • Anaphase • Telophase
Prophase • Longest phase of mitosis • Chromatin condenses into chromosomes • Spindle fibers form and attach to centrioles • Nuclear membrane dissappears • Nucleolus breaks down
Prophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Animal Cell Packages DNA into chromosomes Plant cell Packages DNA into chromosomes ProphaseThe cell prepares for nuclear division
Metaphase • Centromeres line up across the center of the cell • Spindle fibers connect to centromeres
Anaphase • Chromosomes are pulled apart by spindle into individual chromatids. • The chromatids are now considered Chromosomes!!
Anaphase • Centromeres split • Sister chromatids are pulled apart to opposite poles of the cell • Each chromatid is now a separate chromosome