Origins to Multicellular Organisms

Abiogenesis

The theory where living arose from nonliving.

Prebiotic conditions of earth

-Water (oceans) -High UV radiation -Reducing atmosphere gasses -Lightning storms -No free oxygen

4 stages of Abiogenesis

1. Catalysis

2. Self-Assembly

3. Self-Replication

4. Compartmentalisation

Compartmentalisation

Self replicating polymers become surrounded by membranes (Creates unique internal chemistry). Last stage of Abiogenesis.

Self- Assembly

Organic molecules assemble into polymers. Second stage of Abiogenesis.

Self-Replication

Polymers begin to self replicate (enabling inheritance). Third stage of abiogenesis.

Catalysis

Inorganic molecules synthesized organic molecules. First stage of Abiogenesis.

Membrane: Amphipathic phospholipids

The spherical bilayered structure thought to have enclosed the first protocells.

Miller Urey

The experiment that attempted to replicate probiotic conditions on earth.

Goldilocks Zone

The distance the Earth orbits the sun is just right for water to remain a liquid.

RNA

The first Genetic material

RNA Qualities

Self-replicating and catalysis

DNA

Modern day replacement of RNA.

LUCA

Last Universal Common Ancestor

LUCA Evidence

• Alive 2 to 4 billion years ago

• Seafloor Hydrothermal Vents

• Fossils of prokaryotes (~3.7 billion years old)

• Minerals precipitate out

• Hydrogen for energy

• Gene for high temperature

Endosymbiotic Theory

Large Prokaryotes use endocytosis to engulf small aerobic bacteria. Eventually created eukaryotic cells.

Endosymbiont

Cell living inside another cell with mutual benefit.

Evidence for Endosymbiotic Theory

• Mitochondria and Chloroplasts

• Naked & Circular DNA

• 70s Ribosomes

• Same size as bacteria

• Membrane Proteins

Advantages of being a Multicellular Organism

• Exceeds size limits

• High complexity

• Differentiation & Emergent properties

• Longer lifespans

Disadvantages of being a Multicellular Organism

Cancer

Variation of Cell Size in Multicellular Organisms

• Red blood cells are small (7-8 um)

• Neurons (very long but not wide)

• Striated muscle fibers

• Ovum (egg) very large (120um)

• Sperm very small (~um)

Traits of cells that exchange materials in Multicellular Organisms

• Long and flat shape

• Tissues can have villi and microvilli

Characteristics of Stem Cells

• Have self renewal which is the process of continuously dividing and replicating.

• Have potency, this is the ability to differentiate into specialized cell types *necessary for multicellular organism development.

Main types of Stem Cells

• Totipotent

• Pluripotent

• Multipotent

Totipotent

Forms any cell type, develops into new organisms

Pluripotent

Forms any cell type, arising from three germ layers; embryonic and blastocyst

Multipotent

Some closely related cell types “adult”.

Stem Cell Niche

The area where adult stem cells are maintained.

Locations of Stem Cell Niche

• Bone Marrow- Hematopoietic stem cells, Creates blood cells

• Leukemia Treatment

• Hair Follicles- Epidermal stem cells, hair, skin, vascular wound repair

• Burn and Baldness Treatment

Examples of Adult Stem Cells + their Therapeutic Purposes

• Embryonic stem cells- Greater potency, ethical issues

• Adult stem cells- Lower potency, less ethical issues, and low rejection chances

Use of Stem Cells for Therapeutic purposes

Used to replace damaged or diseased cells.

Meristematic Tissue

Found in the tips of roots and shoots, and it is not technically a stem cells.