Foundations of Biology - Cells, Domains, Viruses, and DNA

Flashcards covering microscopy scale, three domains of life, prokaryotic vs eukaryotic structures, bacterial morphology, viral structure/replication, SARS-CoV-2 properties, and DNA/chromatin structure.

What are the mathematical equivalencies for millimeters, micrometers, and nanometers in terms of meters?

1 millimeter is $10^{-3}\,m$, 1 micrometer is $10^{-6}\,m$, and 1 nanometer is $10^{-9}\,m$.

What structural perspective does a scanning electron microscope (SEM) provide compared to a transmission electron microscope (TEM) when viewing tracheal cilia?

Scanning electron microscopy (SEM) reveals the 3D surface structure of cilia projections, whereas transmission electron microscopy (TEM) reveals a 2D thin section through the tracheal cell internal structure.

What are the three major domains of life?

Domain Bacteria, Domain Archaea, and Domain Eukarya.

Which four groups or kingdoms are included under Domain Eukarya?

Protists, Kingdom Fungi, Kingdom Plantae, and Kingdom Animalia.

What are the primary characteristics of prokaryotic cells?

They lack a nucleus, have circular DNA not bound in proteins, may contain plasmid DNA, feature a unique internal cytoskeleton, lack membrane-bound organelles, and are usually single-celled.

What key structural features define eukaryotic cells?

They possess a membrane-bound nucleus, linear DNA organized into chromosomes, membrane-bound organelles (such as the Golgi apparatus and endoplasmic reticulum), and a complex internal cytoskeleton.

What unique cell wall component distinguishes Domain Bacteria from other domains?

Peptidoglycan, a cross-linked amino sugar structure found in the cell wall.

What are the five basic shapes of bacteria?

1. Bacilli (rod-shaped), 2. Cocci (sphere-shaped), 3. Vibrio (comma-shaped), 4. Spirochetes (tight spiral with flexible wall and internal flagella), and 5. Spirilla (loose spiral with rigid wall and external flagella).

How are bacterial cellular arrangements named for Streptococci, Diplococci, Staphylococci, and Streptobacilli?

Streptococci are chains of cocci, Diplococci are pairs of cocci, Staphylococci are clusters of cocci, and Streptobacilli are chains of rod-shaped bacilli.

How do Gram-positive and Gram-negative cell walls differ in structure?

Gram-positive cell walls contain a thick layer of peptidoglycan that retains crystal violet stain. Gram-negative cell walls have a thin peptidoglycan layer surrounded by an outer lipopolysaccharide membrane.

How are Escherichia coli, Staphylococcus epidermidis, and Bacillus cereus categorized based on Gram staining?

Escherichia coli is Gram-negative, while Staphylococcus epidermidis and Bacillus cereus are Gram-positive.

How do bacteria reproduce, and how rapidly can this occur under ideal conditions?

Bacteria reproduce by binary fission (where a single cell splits into two identical cells), which can occur as fast as every $20\,minutes$ under ideal conditions.

What are the three specialized groups of Archaea categorized by their extreme habitats?

Methanogens (live in low oxygen/high methane environments), Thermophiles (live in high temperature environments like geysers and deep sea vents), and Halophiles (live in salt-saturated environments).

What are three key characteristics that define viruses?

They cannot reproduce independently, they are not/do not have cells, and they possess a specific non-cellular structure.

What structural components make up a virus particle?

A viral genome (single- or double-stranded DNA or RNA) enclosed by a protein coat called a capsid (made of capsomeres), and in some cases, an outer viral envelope composed of host-derived lipids and glycoproteins.

What are the primary capsid shapes observed in viruses?

Polyhedral (head-shaped), helical (tail-shaped), and complex (a combination of polyhedral head and helical tail).

What criteria are used to classify viruses?

Host range (determined by cell surface receptors), size, structure, and replication method.

What are the six general steps of viral replication in order?

1. Adsorption (attachment to host receptors), 2. Entry, 3. Uncoating (releasing viral nucleic acid), 4. Replication, 5. Assembly, and 6. Release (via lysis or budding).

What is the primary difference between respiratory droplets and aerosols in virus transmission?

Droplets are larger particles released by coughing/sneezing that land quickly. Aerosols are smaller particles ($\le 5\,\mu m$) that can stay airborne for hours.

What three characteristics of SARS-CoV-2 surface proteins contribute to its success in invading human cells?

1. They act like Velcro to stick strongly to host cell surfaces, 2. They can fold down to avoid detection by the host immune system, and 3. They recruit host enzymes to cut them, changing shape to enter host cells more easily.

How do Molecular (RT-PCR) tests compare to Antigen tests for diagnosing SARS-CoV-2?

Molecular tests detect viral nucleic acid sequences, take hours to days for results, and are highly accurate with virtually no false positives. Antigen tests detect viral surface proteins, deliver results in $15-30\,minutes$, but have a higher false negative rate.

What are the structural levels of eukaryotic chromosome organization from smallest to largest diameter?

DNA double helix ($2\,nm$) $\rightarrow$ Nucleosomes or "beads on a string" ($10\,nm$ fiber) $\rightarrow$ $30\,nm$ fiber $\rightarrow$ Looped domains ($300\,nm$ fiber) $\rightarrow$ Chromatid ($700\,nm$) $\rightarrow$ Replicated metaphase chromosome ($1,400\,nm$).

What are the three chemical parts of a DNA nucleotide, and where are they attached?

A nitrogenous base attached to the 1' carbon of a pentose sugar (deoxyribose), and a phosphate group attached to the 5' carbon of the pentose sugar.

What are the key physical dimensions of the DNA double helix?

The double helix has a diameter of $2\,nm$, nitrogenous bases spaced $0.34\,nm$ apart, and completes one full turn every 10 base pairs ($3.4\,nm$).