Cellular and Molecular Biology

GAIA Hypothesis

The earth is a self-regulating system or acts as one where the living things interact with the environment to keep living sustainably. Living organisms play an active role in keeping Earth habitable.

Panspermia

seeding of the planet

Directed Panspermia (Garbage Hypothesis)

willingful seeding of the planet by a guiding intelligence aka (INTELLIGENT DESIGN)

When was earth formed? (4.5 billion years ago)

The environment was extremely hot. For ex, 10 million celsius to turn Hydrogen to Helium and over 1 billion degrees celsius to form Magnesium.

Primitive Atmosphere

composed largely of nitrogen, water, and carbon dioxide. The early atmosphere was largely reducing (no oxygen in the air). Oxidizing atmosphere acts as an inhibitor for the formation of macromolecules.

Where is iron found?

deep layers of the earth is the ferrous reduced (Fe2+) while in the presence of oxygen iron rusts into (Fe3+).

Reducing atmosphere generated via (volcanic gases)

UV radiation (no ozone layer was present) and iron/sulfur complexes.

Sources of energy included

-Cosmic Rays, Lightning, UV Light, Volcanic Gases, Ionization due to meteorites, Radioactivity, Tides

What gases were believed to represent the major components of the early Earth’s atmosphere in the Miller-Urey experiment?

Methane (CH₄), Ammonia (NH₃), Hydrogen (H₂), and Water (H₂O).

What simulated natural phenomenon was used in the Miller-Urey experiment?

Continuous electric current to represent lightning storms.

How long did the Miller-Urey experiment run before results were observed?

1 Week

What percentage of carbon was converted into organic compounds during the experiment?

10–15%.

What percentage of carbon formed amino acids in the Miller-Urey experiment?

About 2%.

Miller-Urey Experiment Results

the experiment showed that organic compounds such as amino acids (essential to cellular life) can easily be made to under the conditions believed to be present on the early earth.

What are proteinoids, and how were they formed in prebiotic polymer synthesis experiments?

Proteinoids are protein-like polymers formed from amino acids; some showed catalytic activity.

What types of catalytic activity were observed in proteinoids?

Activities similar to ATPase, pyruvate decarboxylase, catalase, and peroxidase.

Under what conditions can RNA polymerize spontaneously?

Only in the presence of specific forms of clay.

What minerals allow activated nucleotides and amino acids to form polymers of at least 50 units?

Montmorillonite, illinite, and hydroxylapatite.

Who discovered ribozymes and when?

Tom Cech in 1982 at the University of Colorado Boulder.

What are ribozymes?

RNA molecules with catalytic activity.

What functions can ribozymes perform?

Cleave nucleotides (RNA or DNA), catalyze RNA polymerization, and promote peptide bond formation.

Why are ribozymes significant in the RNA World Hypothesis?

They show RNA can both store information and catalyze reactions, suggesting an early role in life’s origin.

Which essential coenzymes and enzymes contain RNA nucleotides?

NAD, FAD, CoA, telomerase, and primase.

Tom Cech RNA Discovery

The RNA must be cutting itself hence RNA has catalytic activity (can act as an enzyme on itself)

According to the RNA World Hypothesis, what was likely the first molecule of life?

RNA, because it can self-replicate and act as a template.

Why is RNA suited to be the first genetic material?

It can self-replicate, perpetuate itself, and allow Darwinian selection to begin.

How did early RNAs increase their survival chances?

By interacting with each other and encoding proteins that enhanced their own propagation.

Why did DNA arise later?

DNA is more stable than RNA and became the main template for genome replication.

What major division of processes did the emergence of DNA allow?

Separation of replication (DNA) from translation (protein synthesis).

Is RNA single- or double-stranded?

Single Stranded

How can RNA fold into complex shapes?

Through intramolecular base pairing (complementary regions of the same strand bind).

Why is RNA’s ability to fold important?

Folding allows RNA to form catalytic structures and perform functions like enzymes.

What is a ribozyme?

An RNA molecule with catalytic activity.

What catalytic functions can ribozymes perform?

Substrate binding, cleavage, ligation, and peptide bond formation.

What does ribozyme activity demonstrate about RNA?

RNA can act as both genetic material and an enzyme.

Why are membranes essential for cells?

They form a boundary between the inside and outside environments.

What do phospholipids do in aqueous solutions?

They spontaneously form bilayers.

How did membranes support the RNA World?

Phospholipid bilayers enclosed self-replicating RNA, protecting it and separating it from the environment.

Why did enveloped RNA have an evolutionary advantage over non-enveloped RNA?

The membrane protected it from the environment, increasing survival and replication

What was “pre-RNA” and what replaced it?

A primitive genetic system without ribose and cytosine; replaced by RNA for greater efficiency.

How did RNA give rise to proteins?

Some RNAs evolved the ability to direct protein synthesis.

What role did DNA take on in modern cells?

DNA became the stable genetic repository, proteins took most catalytic functions, and RNA became an intermediate.

Why did subcellular structures like the nucleus evolve?

Compartmentalization increased efficiency by separating cellular processes.

What evolutionary advantage did organelles provide?

Cells with organelles were more efficient than those without.

What new systems arose with early eukaryotic cells?

Transport systems for communication and nutrient acquisition.

How did polysaccharides (sugars) affect early cell membranes?

They strengthened the bilayer, leading to cell walls in bacteria and glycocalyx in some eukaryotes.

What function did proton pumps provide in early cells?

They pumped out protons to control acidity inside the cell.

Why was having multiple proton pumps an advantage?

More pumps improved regulation of acidity, giving survival benefits.