Presentation on theme: "10-1 Cell Growth Growth and Development!!. When Do New Cells Need to Form? A. Growth - More cells B. Maintenance (repair and replacement)--> intestinal."— Presentation transcript:
10-1 Cell Growth Growth and Development!!
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)
Limit of cell size? 1. TOO SMALL - There will not be enough room for all the organelles to carry out the processes needed.
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
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.
Radius 2cm S.A. = ___50cm 2 __ V = __33cm 3 ____ Ratio SA:V = 50:33_or 1.51:1 Radius 1cm S.A. = _____ V = ______ Ratio SA:V = ___ S.A. = 4 (pi) r 2 Radius 1cm S.A. = __13cm 2 ___ V = __4cm 3 ____ Ratio SA:V = _13:4 or 3.25:1__ Radius 3cm S.A. = _____ V = ______ Ratio SA:V = ___ Radius 3cm S.A. = __113cm 2 _ V = ___113cm 3 ___ Ratio SA:V = _113:113 or 1:1__ 1.As the spheres get larger what happens to the SA:V ratio?
3 rd problem: DNA overload
3 rd 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.
Cells Divide at Different Rates The rate of cell division is determined by the body’s need for that type of cell. Nerve cells do not divide because they do not die like our skin cells. A new layer of skin is replaced every 3 weeks. The lining of your intestines has to be replaced often because of the wear and tear. This is also skin cells.
The Cell Cycle and Mitosis
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
M Phase, Cell Division and Mitosis
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
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 - 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.
Chromatin condenses in chomosomes before mitosis begins Chromatin Chromosomes
Parts of Interphase G 1 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 G 2 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.
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
Cytokinesis Cytoplasm divides Two new daughter cells are now separate
Cytokinesis The cytoplasm pinches in half Animal - cleavage furrow Plants - cell plate
In plant cells, a cell plate forms. The cell plate is synthesized by the fusion of multiple membrane- bounded vesicles. Their fusion supplies new plasma membrane for each of the two daughter cells. Synthesis of a new cell wall between the daughter cells then occurs at the cell plate.cell wall
Apoptosis Cell death. Factors that signal genes to produce self destructive enzymes. Not sure why. EX: webbing of toes on an embryo.
Cyclins Protein that controls cell division.. They can make cells grow in a petri dish. Doesn’t work on all cells.
Controls on Cell Division
Cancer Class of disease caused by uncontrolled cell division. Arises when the regulation of the cell cycle breaks down. The cells continue to divide with the absence of internal and external growth factors. Benign tumor: cancer cells remain in one mass and usually can be removed. Malignant: cancer cells break away from the cancer cells to other parts of the body.
Why are cancer cells so dangerous? Cancer cells cannot perform the duties needed by the body. Too many cancer cells and the body cannot perform the processes needed to live. A large tumor can apply pressure to other organs and affect the processes of organ.
What causes cells to form cancer? Cancer cells comes from regular cells that have damage in one of the two genes that makes the proteins for cell cycle regulation. Oncogene: gene that accelerates the cell cycle. Gene 2 : breaks cell cycle. A mutation in these 2 genes can be inherited or a carcinogen can cause a mutation in these genes.
Causes of Cancer Carcinogen: Substances known to cause the cell cycle genes to mutate and cell divide uncontollably. Various forms of cancer have many causes Smoking Radiation Viral infections The common thread in all cancers is that control over the cell cycle has broken down. Over 50% of cancer cells have a defect in the p53 gene.
p53 antioncogene p53 is a tumor suppressor gene found mutated in about half of human cancers. It encodes a gene regulatory protein that is activated by damaged DNA and is involved in blocking further progression of the cell cycle.