SM/ Bio - Le basi dell’organizzazione biologica e molecolare della vita

What are the three core principles of Cell Theory (teoria cellulare)?

1- All living organisms consist of one or more cells.

2- The cell is the fundamental unit of life.

3- All cells arise from pre-existing cells (omnis cellula e cellula).

Why are naked viruses (virus nudi) generally more resistant to disinfectants/solvents than enveloped viruses (virus con involucro)?

Enveloped viruses rely on a fragile outer lipid bilayer (peplos) that is easily destroyed by alcohol, ether, or detergents. Naked viruses have only a sturdy protein capsid (capside).

What three essential viral enzymes are encoded by Retroviruses like HIV?

1- Reverse Transcriptase (trascrittasi inversa)

2- Integrase (integrasi)

3- Protease (proteasi)

Compare the structural cell wall differences between Gram-positive (Gram+) and Gram-negative (Gram-) bacteria.

Gram + : Thick peptidoglycan layer (20-80 nm), contains teichoic/lipoteichoic acids, stains purple.

Gram - : Thin peptidoglycan layer (2-3 nm), possesses an outer membrane with lipopolysaccharide (LPS), porins, and periplasmic space, stains pink.

What is the difference between trasformazione, trasduzione, and coniugazione in bacteria?

Transformation (trasformazione): Uptake of free DNA from the environment.

Transduction (trasduzione): DNA transfer via a bacteriophage (virus).

Conjugation (coniugazione): Direct plasmid transfer between bacteria via a sex pilus (pilo sessuale).

What evidence supports the Endosymbiotic Theory (teoria endosimbiotica) for mitochondria and chloroplasts?

Both organelles contain their own circular DNA, 70S bacterial-type ribosomes, a double membrane, and divide independently via binary fission (scissione binaria).

What is the difference between Glycogen (glicogeno) and Cellulose (cellulosa) in terms of bonds and digestibility?

Glycogen: Made of $\alpha$ -1,4 and $\alpha$-1,6 glycosidic bonds; easily digested by human amylases for energy.

Cellulose: Made of $\beta$ -1,4 glycosidic bonds; structural component of plant walls that humans cannot digest.

Which nitrogenous bases form hydrogen bonds in DNA, and how many bonds connect each pair?

Adenine (A) = Thymine (T): 2 Hydrogen bonds.

Guanine (G) $\ni$ Cytosine (C): 3 Hydrogen bonds.

How do Kinases (chinasi) and Phosphatases (fosfatasi) regulate protein activity?

Kinases: Add a phosphate group (fosforilazione) from ATP.

Phosphatases: Remove a phosphate group (defosforilazione) via hydrolysis.

How do Acetylation (acetilazione) and Deacetylation affect gene transcription?

HAT (Histone Acetyltransferase): Adds acetyl groups, neutralizes histone positive charges, loosens chromatin —> Activates transcription.

HDAC (Histone Deacetylase): Removes acetyl groups, condenses chromatin —> Silences gene expression.

What role does Ubiquitination (ubiquitinazione) play in the cell?

It covalently tags target proteins with ubiquitin molecules, marking them for degradation by the proteasome (proteasoma).