Growth and Development!!

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Growth and Development!!
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.

S.A. = 4 (pi) r 2 Radius 1cm S.A. = _____ V = ______ Ratio SA:V = ___
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. = __113cm2_ V = ___113cm3___ Ratio SA:V = _113:113 or 1:1__ Radius 3cm S.A. = _____ V = ______ Ratio SA:V = ___ S.A. = 4 (pi) r 2 As the spheres get larger what happens to the SA:V ratio?

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.

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

What’s Missing?

M Phase, Cell Division and Mitosis

Cell Cycle http://www.cellsalive.com/mitosis.htm

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

Definitions Histones Telomeres Somatic cells Chromatin Chromosomes
Centromeres Spindle fibers

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
Chromosomes

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

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

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

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Prophase Plant Cell Animal Cell Photographs from:

Prophase The cell prepares for nuclear division
Animal Cell Packages DNA into chromosomes Plant cell Packages DNA into chromosomes

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

Telophase Nuclear envelopes (2) and nucleolus reform
Chromosomes begin to uncoil Spindle fibers disappear.

Mitosis Animation

Animal Mitosis -- Review
Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase

Plant Mitosis -- Review
Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase

Cytokinesis Cytoplasm divides Two new daughter cells are now separate

Cytokinesis The cytoplasm pinches in half Animal - cleavage furrow
Cytokinesis The cytoplasm pinches in half Animal - cleavage furrow Plants - cell plate

In plant cells, a cell plate forms
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.

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.

Oncogenes SRC, proto-oncogene tyrosine-protein kinase

Treatments for Cancer Radiation and chemotherapy – used to kill the cancer cells and stop division. They kill good and bad cells.

Stem Cells Stem cells are a type of body cell that have the ability to
Divide and renew themselves Remain undifferentiated Develop into a variety of specialized cells.