Chapter 4BCD Eukaryotic +Apoptosis+ stem cells Flashcards
(35 cards)
In single-celled eukaryotic cells
use mitosis to reproduce asexually
In multicellular eukaryotic cells
use mitosis for growth and repair
In a nucleus
are 23 pairs of homologous chromosomes.
-Made of chromatins, a long strand of DNA wrapped around proteins called histones.
Interphase (G1, S, and G2)
-Volume of Cytosol increases (G1/2)
-Proteins synthesised for DNA replication (G1)
-DNA is replicated. (S)
-Proteins are synthesised to prepare for mitosis (G2)
In G1 Checkpoint
checks certain criteria to determine if it is ready to progress.
-Large enough
-Not Damaged
-Enough nutrients for mitosis
-Positive cues
In G2 Checkpoint
it checks if the cell is ready for mitosis.
-Proper replication in the S phase
-Enough recourses for mitosis
In M checkpoint
checks if all chromosomes are correctly attached to spindle fibres.
Mitosis
Prophase, Metaphase, Anaphase, Telophase
Telophase
The chromosomes decondense back into expanded chromatin. Nuclear membrane reforms around each nucleus.
Prophase
The chromatin condenses, and the centrioles are separate from each other, forming spindle fibres.
-The nuclear membrane then breaks down as the centrioles move toward the poles of the cell.
-Chromosomes move towards the equator of the cell
Metaphase
The chromosomes are lined along the equator of the cell, and the kinetochore at each chromosome’s centromere extends kinetochore fibres that attach to the spindle fibres.
Anaphase
The spindle fibres shorten, pulling the chromatids away, to the opposite poles of the cell.
Cytokinesis
A contractile ring forms and contracts the cell membrane, membrane vesicles then fuse it together, dividing the cell into 2.
Necrosis
uncontrolled cell death that is unexpected.
-Such as external injury or trauma
Internal environment
the fluid inside a cell in a multicellular organism, such as the red blood cells in our body.
Apoptosis
is programmed cell death, carried out by an ordered sequence of events.
-Allows for removal of cells without spilling contents into the internal environment.
-Failure of this process can lead to cancer
Purpose of Apoptosis
If the cell is damaged or defective
Apoptosis sculpts the body during fetal development
Extrinsic Apoptosis process
-FasL binds to a receptor protein (FasR), which three FasR bind in total.
-This new FasR shape attracts two FADD
-This new shape draws together Procaspase 8
-Procaspase cuts its tip to create Caspase 8
-Caspase 8 binds to Procaspase 3, it then cuts its tip creating Caspase 3
-Caspase 3 cuts the cell cytoskeleton, the framework that holds the cell in shape
Extrinsic Apoptosis
involves a pathway from outside a cell that secretes a death ligand (FasL).
Intrinsic Apoptosis (Mitochondrial Pathway)
begins in the mitochondria and initiates a sequence of events that destroy the cell.
Intrinsic Apoptosis process
-Cytochrome C escape the mitochondria and bind to Apaf1
-Apaf1 then binds to Procaspase 9
-Procaspase 9 splits itself to create Caspase 9
-Caspase 9 binds to Procaspase 3
-Procaspase 3 splits itself to create Caspase 3, to cut the cell cytoskeleton
Blebbing
Little bubbles, or blebs, that contain organelles, form around the cell
-Chromatin in the nucleus condenses
-After the cytoskeleton is cut, the Cell starts to shrink.
Apoptotic Bodies (Disconnected blebs)
break away from the cell.
-The nucleus and chromatin start to fragment
phagocytosis
-Lysosomes in the Phagocytes digest the contents of the cell engulfed.
-Cell content does not enter the environment but stays inside the blebs and is digested within a phagocyte.
