Cell cycle BHARAT INSTITUTE OF TECNOLOGY Mr.B.CHAKRAPANI M.pharm (ph.D) ASSISTANT PROFESSOR DEPARTMENT OF PHARMACOLOGY MANGALAPALLY,IBRAHIMPATNAM(M), R.R Dist.
Apr 24, 2015
Cell cycle
BHARAT INSTITUTE OF TECNOLOGY
Mr.B.CHAKRAPANI M.pharm (ph.D)ASSISTANT PROFESSOR
DEPARTMENT OF PHARMACOLOGY
MANGALAPALLY,IBRAHIMPATNAM(M), R.R Dist.
CELL
Cells
Tissues
Organs
Systems
Organism
Check points and the cell cycle
6-12 h
S G1
6-8 h
G2 M
3-4 h 1 h
Cell Cycle
G1
Cell Cycle
Eric Niederhoffer
SIU-SOM
G0
6-8 h
DNA, RNA, Protein
3-4 h
RNA, Protein
1 h
Mitosis, Cytokinesis
S
G2 Cyc D’sCDK4,6
Cyc B/ACDK1
Cyc ACDK2
M
Cyc ECDK2
6-12 h RNA, Protein
p53pRb
LaminH1Abl
Necrosis vs. Apoptosis
Principle Sites of Damage in Cell Injury
Direct Physical ActionMajor problems are hemorrhage & ischemia
Ionizing Radiation
Ionizes H2O into H+ & OH-
OH- attaches to DNA & prevents cell reproduction
DNA mutations
Toxic Molecular Injury
Dose related
Microbes
Toxins can interfere with protein synthesis or utilization of O2
Inflammatory & Immune Reactions
• Due to cell injury & then in turn causes injury
Stages in cellular response to stress and injurious stimuli
Cell reaction to stimuli
CELL CYCLE
G1 PHASE
G1 Phase– This is the phase in which the cell
spends almost all of its time. It is the normal phase of the cell. The cell is doing what ever that cell was
designed to do. For example: a skin cell would function as a skin
cell during G1 and a liver cell would function as a liver cell during G1.
S PHASE
S phase – the s phase is the phase during
which dna replication is occurring. Out of sight of most people’s ability to see, the
dna is undergoing replication so, at the end
of the s phase, there would be two complete
sets of dna in the nucleus of that cell. In the s phase the cell has copied the contents
of its nucleus
G2 PHASE
G2 Phase- In this phase, the cell makes copies of the important organelles found in the cytoplasm.
If a cell is going to divided, it needs enough mitochondria, (power plants) endoplasmic reticulum, (highways) and so on to support itself after cell division.
If there are not enough mitochondria in one of the new cells, that cell will die and the main purpose of cell division, to make two cells out of one cell, will be for nothing.
In G2 phase, the important organelles in the cytoplasm are copied to ensure that the two new cells will have enough organelles each to survive.
M-PHASE
M Phase- This phase is the phase during
which the nucleus divides into two nuclei.There are four parts to this phase;
1) PROPHASE,
2) METAPHASE,
3) ANAPHASE ,
4) TELOPHASE. At the end of the M Phase, there will temporarily
be a single cell with two nuclei.
PROPHASE
Prophase – Spindle fibers form, Chromosomes shorten, thicken and become visible (under a microscope) and the nuclear membrane begins to dissolve.
PROPHASE
METAPHASE
Spindle fibers move the chromosomes, which have their copies wrapped around themselves, to the middle of the nucleus and line them up.
ANAPHASE
Spindle fibers shorten and pull the identical chromosomes away from each other to the opposite side of the nucleus.
TELOPHASE
Spindle fibers dissolve, chromosomes lengthen out and become invisible again, nuclear membrane reforms around both sets of separated chromosomes.
CYTOKINESIS
The cytoplasm divides leaving you with two identical cells, each with one nucleus.
MEIO
SIS
FOR
MATIO
N
ETIOLOGY of Cell Injury
GENETIC CAUSES
ACQUIRED CAUSES
GENETIC CAUSES
THE GENETIC CAUSES OF VARIOUS DISEASES:
1. Developmental defects
2. Cytogenetic defects: chromosomal abnormalities
3. Single gene defects:Mendelian disorders
4. Multifactorial inheritance disorders
5. Other pediatric diseases
ACQUIRED CAUSES
1. HYPOXIA AND ISCHAEMIA
2. PHYSICAL AGENTS
3. CHEMICAL AGENTS AND DRUGS
4. MICROBIAL AGENTS
5. IMMUNOLOGIC AGENTS
6. NUTRITIONAL DERANGEMENTS
7. PHYCHOLOGICAL FACTORS
HYPOXIA AND ISCHAEMIA
Cells of different tissues essentially require oxygen to generate energy and perform metabolic functions.
Deficiency of oxygen or hypoxia results in failure to carry out these activates by the cells.
Hypoxia is the most common cause of cell injury.
HYPOXIA AND ISCHAEMIA
THE CAUSES OF HYPOXIA ARE AS UNDER:The most common mechanism of hypoxic cell
injury is by reduced supply of blood to cells .i.e. ischemia.
How ever , oxygen deprivation of tissues may result from other causes as well e.g: In anemia , carbon monoxide –poisoning, cardio respiratory in sufficiency, and increased demand of tissues.
All disease occurs because of cell injury
Either because of the injury itself or the repair process that follows
Mechanisms of Cell Injury
Ischemic injury
Principle Sites of Damage in Cell Injury
NECROSIS