BIO151 Lecture Exam 3 - Chapter 26

What are the 3 domains of life?

Bacteria, Archaea, Eukarya.

Which are prokaryotes?

Bacteria and Archaea.

Why are they prokaryotes?

They lack a nucleus.

What key difference is in their cell walls?

Bacteria have peptidoglycan, Archaea don’t.

What about protein synthesis?

Bacteria use formylmethionine; Archaea use methionine.

RNA polymerase?

Archaea's is more complex, like eukaryotes

What are Koch’s postulates?

Steps to link a microbe to a disease

How do they support germ theory?

Show diseases are caused by microbes

What are endospores?

Tough, dormant bacterial cells.

What do they do?

Survive stress like heat and antibiotics

What are extremophiles?

Microbes that live in extreme conditions.

How do scientists separate bacteria, archaea, and eukarya?

By comparing rRNA sequences (16S, 18S).

What shapes do bacteria come in?

Spheres, rods, spirals, chains, filaments.

What does Gram stain do?

Differentiates bacteria by cell wall.

Gram-positive?

Thick wall, stains purple.

Gram-negative?

Thin wall + outer membrane, stains pink.

Gram-positive vs Gram-negative cell wall?

Positive = thick peptidoglycan;
Negative = thin peptidoglycan + 2 membranes

Heterotroph?

Gets carbon from others.

Autotroph?

Makes its own carbon compounds.

Photoautotroph?

Uses light + CO₂

Chemoorganoheterotroph?

Uses organic molecules for both energy and carbon

What are cyanobacteria?

Oxygen-producing photosynthetic bacteria

Fossil role?

Oldest known oxygen producers

Why are cyanobacteria important?

Made Earth’s oxygen, fix nitrogen, feed aquatic life