Bacteria, Archaea, Eukaryotes, Evolution

🧠 EVOLUTION, TRANSPORT, & SIGNALING

Q: What did evolution do to increase the rates of transport and speed of signaling?

A: Evolution introduced:

• Compartmentalization in eukaryotes (e.g., ER, vesicles) to localize and accelerate transport.

• Cytoskeletal tracks (Microtubules) and motor proteins (e.g., kinesin, dynein) for directed transport.

• Myelination of neurons for faster action potential propagation.

• Gap junctions for rapid cell-to-cell signaling in multicellular organisms.

🦠 BACTERIA: STRUCTURE & IMMUNITY

Q: What’s the structural difference between Gram-positive and Gram-negative bacteria?

A:

• Gram-positive: thick peptidoglycan layer, no outer membrane.

• Gram-negative: thin peptidoglycan + outer membrane containing LPS (lipopolysaccharide).

🦠 BACTERIA: STRUCTURE & IMMUNITY

Q: What uniquely bacterial components are recognized by the innate immune system (PAMPs)?

A:

• Peptidoglycan

• Lipopolysaccharide LPS (in Gram-negatives)

• Flagellin

• Bacterial DNA (unmethylated CpG)

🦠 BACTERIA: STRUCTURE & IMMUNITY

Q: What is turgor pressure in a typical Gram-negative bacterium?

A: ~1–5 atmospheres (atm), This pressure pushes against the cell wall and is balanced by peptidoglycan strength.

💊 ANTIBIOTICS & PATHOGENICITY

Q: How does penicillin (a β-lactam) kill bacteria?

A: It inhibits enzymes (transpeptidases) that crosslink peptidoglycan, weakening the wall → lysis from turgor pressure.

💊 ANTIBIOTICS & PATHOGENICITY

Q: How does ciprofloxacin inhibit bacterial growth?

A: It inhibits DNA gyrase and topoisomerase IV, enzymes essential for DNA replication.

💊 ANTIBIOTICS & PATHOGENICITY

Q: What is opportunistic pathogenicity?

A: When normally harmless bacteria (e.g., gut flora) switch to a virulent state in response to stress, population density (quorum sensing), or immune suppression.

🧬 LIPIDS & BIOENERGETICS

Q: How is LPS different from a regular phospholipid?

A: LPS has a sugar-rich outer domain and three fatty acid chains (vs. two in phospholipids). Its phosphate groups trigger immune signaling (TLR4 recognition).

It's asymmetrical and only in Gram-negatives.

🧬 LIPIDS & BIOENERGETICS

Q: Name a phospholipid with more than 2 aliphatic chains.

A: Cardiolipin – has four aliphatic chains and is found in mitochondrial membranes and bacterial inner membranes.

🧬 LIPIDS & BIOENERGETICS

Q: What do bacteria use as their central bioenergetic intermediate?

A: Proton motive force (PMF) – H⁺ gradient across membrane used for ATP synthesis, transport, and motility.

🧬 LIPIDS & BIOENERGETICS

Q:Why does the integrity of the cytoplasmic membrane matter

A: Disruption collapses the PMF, halting energy production and killing the cell.

🧪 ARCHAEA & EUKARYOTES

Q: Which Archaea group is closest to Eukaryotes?

A: Asgard Archaea (e.g., Lokiarchaeota) – share genes for cytoskeletal proteins and trafficking.

🧪 ARCHAEA & EUKARYOTES

Q: What two critical bioenergetic processes evolved in bacteria?

A:

• Photosynthesis

• Oxidative phosphorylation

🧪 ARCHAEA & EUKARYOTES

Q: What two endosymbiotic events led to organelles in eukaryotes?

A:

1. Mitochondria from an α-proteobacterium

2. Chloroplasts from a cyanobacterium

🧪 ARCHAEA & EUKARYOTES

Q: What’s the evidence for mitochondrial/chloroplast endosymbiosis?

A:

• Own circular DNA

• Double membranes

• Ribosomes similar to bacteria

• Reproduce via binary fission

🦠 PROTOZOANS, MOTILITY, DEVELOPMENT

Q: What two methods of handling osmotic forces and locomotion evolved in protozoans?

A:

• Cilia/flagella (powered by dynein and microtubules)

• Amoeboid movement (actin polymerization)

• Contractile vacuoles for osmoregulation

🦠 PROTOZOANS, MOTILITY, DEVELOPMENT

Q: How did these motility modes shape animals?

A:

• Flagella/cilia → sperm cells, airway cilia

• Amoeboid → immune cell crawling (white blood cells, macrophages)
  → Some organisms (e.g., protists and flatworms, annelids) retain both types.

🧫 ANIMAL TISSUES & EVOLUTIONARY DIVISIONS

Q: What three tissues formed in primitive animals with a digestive chamber?

A:

• Ectoderm (skin, neurons)

• Mesoderm (muscles, organs)

• Endoderm (gut lining)

🧫 ANIMAL TISSUES & EVOLUTIONARY DIVISIONS

Q: Differences between Protostomes and Deuterostomes?

Feature	Protostome	Deuterostome
First opening becomes…	Mouth	Anus
Cleavage	Spiral, determinate	Radial, indeterminate
Examples	Insects, worms	Vertebrates, echinoderms

🧫 ANIMAL TISSUES & EVOLUTIONARY DIVISIONS

Q: When did this division btn protostome and deuterostome occur?

A: About 540 million years ago during the Cambrian explosion.

🧬 GENETIC DIVERSITY & REPRODUCTION

Q: Clonal growth provides slight variation. How do bacteria achieve genetic diversity?

A:

• Transformation (uptake of free DNA)

• Conjugation (plasmid transfer via pili)

• Transduction (phage-mediated DNA transfer—via viruses)

🧬 GENETIC DIVERSITY & REPRODUCTION

Q: Advantages of polyploidy and sexual reproduction?

A:

• Polyploidy: Increased gene copies → gene redundancy= mutation buffer, greater resilience

• Sexual reproduction: Genetic recombination → more variation → better adaptation to environmental change

💊 ANTIBIOTICS & PATHOGENICITY

Q: Opportunistic pathogenicity: How does switching to virulent behavior occur in bacterial populations?

A: Via quorum sensing—when bacteria detect high population density through autoinducers, they activate genes for toxins, adhesion, biofilms, etc.

🔹 LPS vs. PHOSPHOLIPIDS

Q: What do the phosphate groups on LPS do?

A: They stabilize LPS via divalent cations (Mg²⁺/Ca²⁺) and are recognized by TLR4 in the immune system.