Lesson 1: Foundations to Set the Stage
Focusing on Cellular Structure and Function
The Normal Cell Cycle
-The cell cycle refers to the
... [Show More] ordered seres of processes of DNA replication and mitosis, or cell division
-Cell nucleus regulates these processes by gathering and processing complexes molecular information
Interphase and Mitotic Phase
Cell division produces two identical cells through these two major phases
During interphase:
Cell grows and DNA is replicated through the following three steps:
1: First growth phase (G1 or first gap)
2: Synthesis phase (S phase)
3:Mitotic Phse (M phase)
First Growth Phase (G1 or first gap)
-cells increase in size
-reproduce RNA
-"quality assurance" test that the cell will be ready to synthesis DNA
-Length of time is variable, can be from hours to days
Synthesis Phase (S phase)
-DNA replicates
-Results in the formation of identical pairs of DNA (chromatids)
-which are attached a t the centromere
-lasts 2-10 hours
Mitotic Phase (M phase)
-Replicated chromosomes are aligned, separated, and move into 2 new, identical daughter cells
-takes about 30-60 minutes
Major points of cell regulation are entry and exit from
-G1 checkpoint
-S Phase
-G2 checkpoint
-M phase
Restriction Point
-The transition from the resting phase into an actively dividing phase (G0-G1) is a point where cellular transformation can occur
-During this time, cells pass through a transition phase known as a restriction point
-Extracellular growth factors trigger reentry into G1, and GF are required to send the cells past the restriction point, or the point of no return
G0 Phase (resting phase)
-After mitosis, cells may enter back into the G1 phase or go into a resting phase, known as G0
-Most cells in the human body reside in G0
-Exceptions to this are those that are (Resting in G0 phase)
-Exceptions to this are those that are metabollically active, such as
-granulocytes
-and the epithelium of the GI tract
Cell Cycling Time
Amount of time from mitosis to mitosis
Cell cycle video and image
http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cycle_works.html
Check points in the Cell Cycle: Keeping it All Under Control
-The cell cycle is carefully controlled through a series of checkpoints
-Variation in duplication or distribution of chromosomes during cell division can alter the genetic information passed on to daughter cells, leading to cellular dysfunction and disease, such as cancer
-These checkpoints monitor for DNA integrity and control progression through mitosis
Progression through the cell cycle is controlled through two proteins:
1. cyclines (D, E, A, B)
2. Cyclin-dependent kinases (CDKs)
-Cyclin-CDK complex allows the cell to progress through each phase of the cell cycle
Locations of proteins Cyclins (D, E, A, B) and CDKs
-(G0-G1) : Cyclin D and CDK 4/6
-Early S: Cyclin E and CDK 1/2
-Late S: Cyclin A and CDK 1/2
-G2: CDK 1/2 and cyclin A
-Before M: CDK 1 and Cyclin B
Inhibitory proteins
-prevent progression of the cycle when DNA damage is detected
-An example of an inhibitory protein is p53 (AKA TP53)
DNA Damage Checkpoints
-If DNA damage is present, cells are programmed to stop dividing or undergo apoptosis (programmed cell death)
-The retinoblastoma protein (Rb), p53, and p21 are some of the most well-understood inhibitory proteins (IP)
Inhibitory proteins p53
-Levels of this IP regulate several important target genes
-Will increase when DNA damage is present
-Protects against inappropriate signal proliferation
-sometimes called the "suicide gene"
M Phase Checkpoints
When the cells prepare to divide, the chromosomes line up in the mitotic spindle.
If the chromosomes are not properly aligned, division is not allowed to continue
Immunity
Cells of the Immune System
Pluripotent Stem Cell
-The cells of the immune system are created in the bome marrow from what is know as a ___
-A stem cell that can differentiate into any cell type except for extraembryotic tissue, does not yet have a function
Myeolid Precursor Cells
Mature into:
-RBCS
-Plts
-WBCs (Granulocytes)
Lymphoid Precursor Cells
Mature into:
-Specialized WBCs called lymphocytes (Agranulocytes)
Lines of Defense: The Immune System's Response to Attack
Consists of 2 types of immunity:
1: Innate
2: Adaptive
Innate Immunity
-First line of defense against a pathogen
-Does not retain memory of the entity
-Involves the following:
(skin, mucous membranes, and normal flora of the skin and gut)
(Cellular components such as phagocytes, natural killer cells, granulocytes, and macrophages)
1. Phagocytes
2. Natural Killer Cells
3. Granulocytes
4. Macrophages
1.Cells that engulf and destroy invader
2. Cells that sense receptors on self and non-self to determine if they should kill or not
3. Type of WBC that have granules (Neutrophils
Eosinophils - parasites
Basophils - release histamine to stimulate immune response)
4. Large phagocytic cells stimulated by infection
Adaptive Immunity
-Stimulated if innate immunity is insufficient
-leads to immune system memory
-Humoral immunity
-Cell-mediated immunity
-Regulatory T-cells
Humoral Immunity
-B-Cells
-Memory B-Cells
-Plasma act to produce immunoglobulins (Igs) or antibodies
B-Cell
-each one is programmed to make one specific antibody
-Can recognize antigens whether they are freely circulating in the blood or attached to surface of a microbe
-When dividing, can become plasma cells which will then begin secreting antibodies that are unique to that antigen [Show Less]