Mitosis

A cell undergoing mitosis goes through Prophase, Metaphase, Anaphase and Telophase.

Interphase:This stage prepares the cell for mitosis. The nucleus in this stage is well defined and has DNA loosely packed in long chromatin fibers. This stage is when the cell is preparing for mitosis, and replicates chromosomes and produces proteins and organelles. During the synthesis phase of interphase, the dividing cell replicates and must separate DNA copies correctly to two daughter cells. The DNA is then organized into chromosomes. After the DNA is copied, the chromatin condenses and makes a smaller package. A mitotic chromosome is a duplicated chromosome and it contains two sister chromatids which contain identical copies of DNA.

Prophase: In this stage, the chromatin condenses and the chromosomes are visible. The centrioles move to opposite poles of the cell (in the animal cell) and the protein fibers cross the cell to form mitotic spindles, also called microtubules which are made of actin and myosin. During this stage, the nucleolus disappears and the nuclear membrane breaks down.

Metaphase: the early stages of this phase are known as prometaphase. This is when the spindle fibers attatch to the centromeres, creating kinetochores. Microtubules attatch at the kinetochores and connect the centromers to the centrioles. Then the chromosome begins moving, and enters into Metaphase. Metaphase is when chromosomes align along the middle of the cell. The spindle fibers coordinate the movement and help ensure that the chromosomes separate properly.

Anaphase: The sister chromatids separate at the kinetochores. They are pulled at the centromeres and move to opposite poles. They are pulled by motor proteins "walking" along microtubules. These proteins are actin and myosin, and this also phase also has an increasement of ATP by mitochondria. The poles move farther apart and the microtubules lengthen. A separation off chromatids occurs in anaphase as well, where the proteins holding together sister chromatids are inactivated.

Telophase: This is when chromosomes arrive at opposite poles and daughter nuclei form. The nucleoli then form and the chromosomes disperse and are no longer visible under light microscope. The spindle fibers disperse and cytokinesis begins.

Cytokinesis is cell division. In animals it is a constriction belt of actin microfilaments around the equator of the cell. The cell is split into two. In plants a cell plate forms, and the vesicles line up at the equator. A new cell wall is laid down between the membranes, and the new cell wall fuses with the existing cell wall.

The Cell Cycle.

Cell Division..........................Why?
- To make new cells
- Continuity of life: Asexual reproduction, growth, repair, and renewal
- Cell cycle: Make a copy of a preexisting cell (Daughter cells)



What's in a cell that smells so sweet.......ehhh







- Nucleus: Chromosomes, DNA
- Cytoskeleton: "Scaffolding" or "Skeleton"; The internal framework of a cell, composed largely of actin filaments and microtubules (spindle fibers). Also includes Centrioles (in animaks).



The Nucleus:
Its function: to protect DNA

It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these chromosomes are the cell's nuclear genome. The function of the nucleus is to maintain the integrity of these genes and to control the activities of the cell by regulating gene expression.

The Nuclear Envelope: a double membrane that contains pores to allow large marcromolecules to pass through such as ribosomes.

The Cytoskeleton:

Its function: to provide structural support, maintain shape of cell, provide anchorage for organelles via protein fibers (microfilaments, intermediate filaments, and microtubules).

The cell may become motile by cilia, lamellipodia or flagella.

The cytoskeleton also organizes structures within the cell and its activities.

Centrioles:

One of two cylindrical cellular structures that are composed of nine triplet microtubules and form the asters during mitosis.
Centrioles are involved in the organization of the mitotic spindle and in the completion of cytokinesis.
Centrioles are an important part of centrosomes, which are involved in organizing microtubules in the cytoplasm.



They organize spindle fibers and guide chromosmes in mitosis.


Daughter Cells:
During mitosis, an exact copy of DNA is made from the parent cell to be passed to the daughter cells.
Cytokinesis: division of orgnanelles and cytoplasm





Mitosis:

Interphase: Defined only by the absence of cell division. During interphase, the cell obtains nutrients, and duplicates its chromatids. Most eukaryotic cells spend approximately 90% of its life in Interphase. "Every day job": produces RNA, synthesize proteins and enzymes, prepares for duplication if triggered.

Prophase: Stage during which the chromosomes condense and become visible, the nuclear membrane breaks down, and the spindle apparatus forms at opposite poles of the cell.

Pro-Metaphase: The stage of mitosis or meiosis in which the nuclear membrane disintegrates, the centrioles reach the poles of the cell, and the chromosomes continue to contract.

Metaphase: Condensed chromosomes align in the middle of the cell before being separated into each of the two daughter cells.

Anaphase: The chromosomes move from the equatorial plate toward opposite ends of the nuclear spindle.

Telophase: The chromosomes of daughter cells are grouped in new nuclei.

Cytokinesis: The division of the cytoplasm of a cell following the division of the nucleus.


Cell Life Cycle:





















Interphase:
Divided into three phases:
-G1: first gap
Cell doing everyday job
Cell grows
-S: DNA Synthesis: Copies chromosomes
-G2: second gap
Prepares for division
Cell grows more
Produces organelles, proteins, and membranes







FIN




Oh tomorrows sherpa is...............Maria

Science Debate 2008

Have you seen this:
http://sciencedebate2008.com

Would be great if you students got to see this.
==========================================

Universities, corporations and a host of individuals are calling for a debate with all four of the remaining presidential candidates discussing critical scientific issues that impact everything from the environment to the economy.

Sciencedebate2008.com, formed by two Hollywood screenwriters who had time to mull science recently while on strike, is an effort aimed at thrusting technology into the limelight.

One of the initiative's founders, Shawn Otto, said yesterday more than 17,000 American universities and the editors of nearly every major science publication in the nation have added their names to the Web site, encouraging the presidential hopefuls to debate key scientific issues.

"This is a nonprofit organization we set up to raise the profile of science and technology in our national political diaglogue," Otto said, adding that his initiative is now being co-sponsored by the National Academy of Sciences, the Institute of Medicine, the National Academy of Engineering, the Council on Competitiveness and the American Association for the Advancement of Science.

Yesterday, John Podesta, chief of staff for former President Bill Clinton, posted a video statement on YouTube echoing that science remains one of the nation's primary areas of focus. He called for a presidential debate "in charting a path forward on national security, on energy and climate change policy, really on the core fundamentals of our economic policy."

Otto said it would be "really fabulous" to see Democrats and Republicans on the same stage debating issues in science.

"All of us believe that almost every major policy challenge that the next president will face revolves around questions of science and technology," Otto said, referring to signers of his initiative.

"Ever since World War II, America has been leading in science and technology, and science and engineering have driven half of our economic growth."

But in the not-too-distant future, he added, 90 percent of all scientists will be living in Asia, causing a major "shift in intellectual capital."

James McCarthy on Science Debate 2008



John Porter on Science Debate 2008



Francesca Grifo on Science Debate 2008

THE ENDOCRINE SYSTEM: HORMONES

The Endocrine System is basically a communicating system for the body. Multicellular organisms need to communicate from cell to cell to maintain homeostasis. Hormones are used in regulation. The other regualting and communicating system is the nervous system. Cells interect with each other through neurons. An electrical signal is released by ions flowing through a membrane. Neurons have fast, short-lasting responses. Hormones have slow, long-lasting responses. Hormones are chemical mesesengers that are released in one part of the body and affect another part of the body. Hormones have long term effects such as in

• metabolism
• growth
• development
• maturation
• reproduction

Hormones are released by ductless glands. Ductless glands are tissies that produce hormones and release the hormones directly into the bloodstream. Duct glands like the pancreas produce the enzyme and release them into another area through tubes like how the pancreas releases into the intestine. Hormones are specific to the target cell. Another theme is seen here, the lock and key mehtod. The hormone fits into the receotor proteins that the hormone attaches to specifically only to ones that have the shape that can fit with the hormone.

There are 2 major types of hormones:

1. Protein-based Hormones

These hormones are made of proteins including polypeptides suc as insulin and ADH (anti diuretic hormone). Glycoproteins are toher protein hormones that have proteins and carbohydrates. These include FSH (Follicle stimulating hormone) and LH( luteinizing hormone). Amines are another type which are modified by amino acids like epinephrine and melatonin. Protein based hormones are hydrophillic and are not lipid soluble. That means they can't diffuse across a membrane. The protein hormone has to bind to receptors on top of the plasma membrane that are embedded in the membrane. The homrone fits into the protein in the membrane and causes a conformational change. The protein that receives the hormone stimulus changes chape which causes another protein at the other end to carry the message along. This secondary messenger pathway is triggered. Enzyme action, uptake or secretion of molecules is activated.

2. Lipid-based Hormone

These hormone include steroids which are modifed cholesterol such as sex hormones and aldosterone. Lipid based hormones are hydrophobic which means they are lipid soluble. They can diffuse right through the cell membrane without being stopped at the cell membrane and having to go through a receptor on the membrane. These hormones bind to receptor proteins in the cytoplasm and some on the nucleus. Lipid hormones bind to DNA as transcription factors. The hormone causes a conformational change. The transcription factor is the protein on the DNa that coordinates which genes should be transcripted onto the mRNA to make a protein. Lipid hormones are carried on a protein carrier because they are not soluble in water since oil and water don't mix. The hormone can cause a major long term change in the body such as growth. The growth factors can affect hair, bone, muscle and gametes.

Oh Yeah Tuesday night's sherpa will be Shannah.

Well, well, here it is--the missin' blogs: B CELLS (2/6) & T CELLS (2/8)

WOO HOO THE 3rd Line of Defense is Acquired Immunity B CELLS & T CELLS

Well first and formost i would like to appologize to my fellow class mates as i always do for not having the sherpa repost in on Time.... ma bad. Well the library is a quiet place to work so i guess this is where i'll be writtin from.

Iight:

..... The 3rd line of defense in the immune system is Acquired Immunity which consists of specific defenses: lymphocytes (B cells and T cells) and antibodies(immunoglobulins).

This defense mechanism is activated in reponse to antigens on pathogens that are not recognized as self-cells or home-cells.

Antigens are proteins that serve as nametags for the t cells and b cells to recognize if a cell is a home cell or a foreigner.

B Cells mature in the bone marrow and belong to the humoral (body fluids) response system.
T cells mature in the thymus and belong to the cellular response system.

B Cells
There are two types of B cells: plasma cells and memory cells. The plasma cells produce anitbodies and make memory cells. The memory cells have a long term immunity to a specific antogen. They are the defense against attackers that are floating freely in the lymph and blood.

Antibodies: proteins that bind to specific antigens.
IgM: 1st immune response.
IgG: 2nd immune response: more antibodies in plasma
IgA: in external secretions
IgE: release of histamine, triggers allergic reactions

B cell immune response system.

T Cells

An immune response to infected cells(pathogens inside cells).

They are the defense against non-self cells.

The two types of T cells are Helper T Cells and Killer T Cells.

Helper T Cells alert the immune system of intruders.

Killer T Cells attack the infected body cells

T cells know that a cell is infected when there are antogens of a foreign invader on the outside of the cell. The infected cell digests the pathogen and the MHC carry the pieces to the surface kind of like a wanted poster.

The Helper T cell then releases interluekin 1 to produce more helper t cells to look for more infecter cells. It also releases interleukin 2 to alert the Killer T cells that there is an invader. This activates the Killer T Cells. The interleukin 2 also stimulates B cells to drop more anti bodies in case there are whole pathogens in the humoral system.

The killer t cells destroy the infected target cell by making holes in it (apoptosis). Since the membrane is now punctured the cell is no longer semi permeable it is wholy permeable and water rushes in from a hypotonic solution to a hypertonic solution and the cell pops.

THATS ALL FOLKS

PS If youre really feeling like a nerd play an immune system game:
http://nobelprize.org/educational_games/medicine/immunity/index.html

Monday Nights Sherpa Will Be SAAD. =)

Since someone did not post a sherpa last night i am now stuck with this job, and ofcourse im thrilled!!! =)

B cell immune response

-plasma cells = fast response


-clone

-release antibodies (proteins)

-memory cells = long term immunity

VACCINE'S

Vaccinations have proven to be a successful way to fight virus'. A person is exposed to a small amount of the virus which is not enough to be a danger to them. This is the beginning of active immunity. In other words resistance to the disease or infection. The body then makes antibodies against the antigens that are causing the disease. The antibodies work to get rid of foreign invaders. Jonas Salk developed the first vaccine which was against polio (which attacks motor neurons).

JONAS SALK

BREASTFEEDING (MATERNAL IMMUNITY)

Breastfeeding is a way of a child obtaining antibodies from their mother. Breast milk protects infants from bacteria and virus. It also helps the baby fight off infection and disease. They can also be passed across the placenta. This makes breastfeeding a very important contributor to a childs health.

-kerrie- p.s.- the sherpa for tom. will be saad

Immune/ Lymphatic system 1

Today we learned about the immune and lymphatic system.

There are many avenues of attack for foreign substances to enter your body.

1. digestive system
2. respiratory system
3. urogenital tract
4. break in the skin

Once their in your body they can either use the circulatory system or the lymph system to go around your body. A body needs an immune system to protect it from viruses, bacteria, fungi and protists that are going to use the body as a tasty nutrient & a vitamin-packed meal. Also your body can be attacked from the inside by abnormal body cells like cancers. The lymph system is made fore the production and transportation of leukocytes and to trap foreign invaders. Only white blood cells travel through this system. It consists of lymph vessels which are intertwined amongst blood vessels , and lymph nodes which are made to collect foreign invaders.

Red and white blood cells are made from pluripotent stem cells in the bone marrow. These stem cells are then made into lymphoid stem cells and myeloid stem cells. The myeloid stem cells make red blood cells , basophils, eosinophils, neitrophils, monocytes, and platelets. Lymphoid stem cells make either B-Cells or T-Cells. B & T cells are the true immune system.

The first line of defense

Broad, external defense. such as walls and moats. this is the skin and mucous membranes. The skin includes external and external skin.

The physical and chemical defenses are non specific. The external barrier are epithelial cells and mucus membranes such . Examples are the skin, the respiratory system, the digestive system and the urogenital tract.

The chemical carriers on the epithelium are skin and mucous membrane secretions. Sweat, tears, mucus, saliva, stomach acid and anti-microbial proteins (such as lysozyme enzyme)

The Second Line of defense inclcludes internal, broad range patrol by many different cells and proteins such as mast cells, monocytes, macrophage and natural killer cells.

Leukocytes or phagocytic WBC's. Their attracted by a chemical signal released by damaged cells. Neutrophils are the most abundant and have a three day life span. Macrophages are "big eaters" and are long-lived. Natural killer cells destroy virus-infected cells and cancer cells.

In order to kill cells tho have gone bad , natural killer cells perforate cells, by releaseing perforin ( a protein) into the membrane of a target cell.. This forms a pore allowing fluid to flow into the cell. The cell then ruptures or lysis. This is call apoptosis. As Ms. Foglia says, its like "causing a cell to commit suicide"

Anti - microbial proteins awork as a complement system. 20 proteins circulating in blood plasma attack baterial and fungal cells. This forms a membrane attack complex which perforates target cells which also leads to apoptosis.

Inflammatory response is when damage to tissue triggers local non-specific inflammatory response. The cells then release histamines and prostaglandins. Capillaries then dilate and become more permeable This : increases blood supply, delivers WBC, RBC, Platelets & clotting factors. This accounts for swelling, redness and heat of inflammation & infection.

i cant get pictures because my computer is being difficult, i'm sorry this was boring, BUT tomorrow's sherpa will beeeeeeee...... KIM :)

GoodNight.