Cell Cycle, Regulation, Death, Checkpoints, Asexual Reproduction

Purpose of cell reproduction

Growth, repair, and replacement of cell loss

Prokaryotic VS Eukaryotic

Prokaryotic= no membrane bound organelles or nucleus (DNA stored in nucleoid.

Eukaryotic= membrane bound organelles and membrane bound nucleus

Cell size

High SA:V allows faster and efficient material exchange, low SA:V means that it decreases it’s efficiency.

Mitochondria: provides energy for the cell

Endoplasmic reticulum: synthesizes proteins and lipids

Golgi Apparatus: synthesizes and packages proteins and lipids

Lysosomes: break down waste

Structure and specialisation of plant and animal cells

Plants use photosynthesis for energy whilst animal cells possess lysosomes and centrosomes who rely on the mitochondria for energy production.

Cell replication an ASEXUAL process

• Requires only 1 cell

• Producing two genetically identical daughter cells in PROKARYOTES

• Known as binary fission

• Process is simpler and faster than asexual reproduction in eukaryotic organisms

Steps of Binary Fission in Prokaryotic cells

1. Replication of the circular DNA chromosome and cell elongation occurs

2. Two cellular chromosomes migrate to either ends of the cell

3. Cell membrane pinches in two and a cell wall (septum) forms along the middle, extends and breaks to form two cells

Eukaryotic cells: reproduction of two identical copies of the parent cell being produced

Apoptosis

Controlled process of programmed cell death for cells no longer needed or DNA that cannot be repaired, active process, pre-defined suicide, webbing skin cells dying.

Shrinks and breaks into small, membrane bound pieces (apoptotic bodies) and are engulfed by neighboring cells.

Cell cycle disruptions

Disruptions can result: uncontrolled cell division and cancer

Apoptosis malfunctions can result: cancers, neurodegenerative disorders, autoimmune diseases

Cancer cells characteristics

Invading and spreading to other tissues

Disregarding apoptosis signals

Infinitely multiply

Uncontrolled growth

Mechanisms of Apoptosis

Intrinsic (internal) signal within the cell- known as the mitochondrial pathway

Extrinsic (external) signal from a source outside the cell- known as the death-receptor signal.

Apoptosis Mechanisms set off biochemical pathway

Cell shrinkage

Formation of protusions of the cell membrane (blebs)

Formation of apoptotic bodies or clean up through phagocytosis (white blood cells)

NO INFLAMMATION

Necrosis

Uncontrolled, die as a result of an acute injury, swell and burst, spilling their contents that can potentially cause a damaging inflammatory response, untimed suicide, frostbite

Cell cycle

G1: Cell growth

S: DNA replication

G2: Prepping for mitosis

Cell division: Mitosis

REPEAT

Cycle Length in 24 hrs

G1= 11 hours

S=between 8 hours

G2=between 4 hours

Mitosis= 1 hours

G1 Phase:

Cell grows and undergoes normal functions, preparing for DNA replication

Checkpoints: is cell large enough? Recieving positivie cues? DNA damage? Won’t go through if any of these are checked off.

S phase:

DNA replication occurs, each chromosome duplicating into two sister chromatids

G2 Phase:

Cell growth continues and prepares for mitosis, ensuring DNA is replication is complete

Checkpoints: DNA damage? DNA completely copied, proteins are binded to DNA to be carried.

Mitosis Phase:

IMPAT (interphase,prophase,metaphase,anaphase,telophase)

Checkpoints: Chromosomes aligned in metaphase? Sister-chromatids correctly attached to spindle microtubles? Chromatids seperated properly in anaphase?

Cell cycle in Eukaryotic cells

Cell Growth (G1) → DNA replication (S) → Preparation for Mitosis → Cell division (M)

Stem cells

Possess two properties that allow them to make more cells like themselves- self renewal, and becoming other cells

Totipotent: differentiate into ANY cell

Pluripotent: differentiate into most cells

Multipotent: differentiate into multiple related cell types in a specific lineage

Unipotent: differentiate into a specific cell type