Unit 1 Origin and Evolution of Cells

What structural component do all cells have in common

1. Plasma membrane

2. Cytoplasm

3. Ribosome

4. Genetic material (DNA)

What do Prokaryote cells have

Have three things:

1. Plasma membrane

2. Nucleoid ( a region where genetic material is)

3. Ribosomes

4. Usually have a cell wall

What they don’t have:

1. No membrane-bound organelles

2. No Nucleus

What do Eukaryote cells have

What they have:

1. Nucleus

2. Cytoskeleton

3. Membrane organelles

4. Plasma membrane

5. Ribosomes

Some Eukaryotes (Plant cells)

1. Plastids

2. Large vacuoles

3. Cell walls

What is the Cytoskeleton for

It provides structural support, helps determine cell shape and organize the cytoplasm, and contributes to cell movement.

What is the order in how the first cell arised

1. Early Earth

2. Organic Molecules

3. Compartmentalization

4. RNA world/Protobionts

5. Natural selection

6. LUCA

7. Evolution of cells

Early Earth

The early atmosphere contained Carbon dioxide (CO2) and Nitrogen (N2) with little levels of hydrogen, hydrogen sulphide
and carbon monoxide.

With little to no free oxygen

Organic Molecule: Stanley Miller experiment.

A spontaneous formation of organic molecules happened when electric sparks into a mixture of H2, CH4, and NH3, in the presence of water.

What can happen to organic molecules under prebiotic conditions

Under prebiotic conditions macromolecules would spontaneously polymerize. For example heating dry mixtures of amino acid forms to polypeptides.

Compartmentalization

The formation of membrane-like compartments that enclosed molecules and allowed chemical reactions to occur in a more organized environment.

RNA world hypothesis

RNA is capable of catalyzing a number of chemical reactions (Acts as a catalyst)

RNA serve as a template and to catalyze its own replication (Hold genetic information)

Protobionts or Protocells

Not alive cell structures in which molecules were enclosed within membrane-like compartments, creating an organized environment for chemical reactions

Natural Selection

Variations among protobionts could cause some to survive and reproduce more successfully than others, causing advantageous traits to become more common over generations.

LUCA

LAST UNIVERSAL COMMON ANCESTOR

which is the most recent single-celled population from which all current life on Earth descends

Why DNA and not RNA

Double strand: Provides a complementary template to check if one of the strands are damaged

Deoxyribose: Makes DNA more chemically stable

Thymine: Can make it easier to recognize any damage on the strands

Repair Enzyme: Can detect and repair DNA damage on the strands

Evolution of metabolism in cells

Cells were in a sea full of organic molecules and couldn’t form their own energy. This limited them to their environment therefore they created their own metabolic pathway to form energy (ATP).

1. Glycolysis (Used in anaerobic)

2. Photosynthesis (Used from sunlight producing O2)

3. Oxidative Metabolism (Used in aerobic)

Endosymbiosis theory.

Where an organism cell lives in another as they both benefit each other.

It proposes that mitochondria and plastids originated from free-living bacteria that were engulfed by ancestral eukaryotic cells and eventually became permanent organelles.

Evolution from LUCA to LECA

A prokaryote cell had its plasma membrane fold inward and made nuclear membrane, ER, and golgi apparatus.

Then the cell did endosymbiosis and engulfed an aerobic bacteria that eventually became the mitochondria in the cell.

This formed LECA (LAST EUKARYOTE COMMON ANCESTOR)

How did LUCA create plant Eukaryotic cells

Through endosymbiosis involving a photosynthetic bacterium, which eventually became a plastid.

Multicellularity

Unicellular cells evolved multiple time to become multicellular. It happened through associating with other cells. Evolution didn’t occur once it occurred multiple times.

How can one single cell give rise to a multicellular organism with many types of diverse cells

By cell specialization, which is cells having specific roles and this is a result of cell differentiation

Cell differentation

The process where young unspecialized cells take on individual characteristics (DIFFERENTATION) and reach their mature form and function.