M250 Exam 1: Perspectives and Microscopy

What is microbiology? What are the 6 categories?

study of small (microscopic) organisms

• bacteria (the focus of M250)

• archaea

• protists

• algae

• fungi

• viruses

What is an organelle?

membrane-enclosed sub-compartment (that bacteria don’t have)

What do bacteria have instead of a nucleus?

nucleoid

What kind of chromosome do bacteria have?

single, circular

What’s the difference between eukaryotic ribosomes and bacterial ribosomes?

eukaryotic are 80S and bacteria are 70S

What’s special about bacteria’s cell wall?

peptidoglycan

What do bacteria do? (in simple words)

consume and grow

What do bacteria consume?

sugars, light, toxins, metal

some can make alcohol

some breathe uranium

they can eat and breathe basically anything when combined

Where do bacteria grow?

Everywhere and all the time but many are in conditions that are “extreme”

• hot springs

• arctic ocean

• strong acid

• high in atmosphere

• deep in Earth

What do bacteria do? (in more detailed words)

• cycle most carbon

• make the most oxygen

• fix all the nitrogen

• some make us sick but most keep us healthy

• primary decomposers (consume!!)

• build communities and copperate

• prey on each other too

Who is credited with discovering microorganisms?

Antony van Leeuwenhoek (1676)

What is the Voynich Manuscript?

book of “weird” drawings, unknown language, drawings of early microscopes, maybe the first micro textbook?

What are the requirements for microscopy?

• magnification

• resolution

• light quality

• contrast

What’s the relationship between focal length and magnification?

as focal length decreases, magnification increases

What’s the relationship between numerical aperture and resolution?

as numerical aperture increases, resolution also increases

What is a gram stain?

detects kind of cell envelope

What is phase contrast microscopy?

uses diffraction and interference to generate contrast, no staining necessary

What is transmitted light microscopy?

light passes through the specimen

What is fluorescence microscopy?

• light does not pass through specimen

• light excites fluorescent molecules which then emit light themselves

• different parts are stained with different colors

What’s the difference between fluorescence and luminescence?

fluorescence

• emits light after photo-excitation

• example: GFP

luminescence

• produces light by chemical reaction

• example: Luciferase

What’s the relationship between wavelength and resolution?

as wavelength decreases, resolution increases

(objects smaller than wavelength cannot be separated)

What is atomic force microscopy? (AFM)

an ultra-fine probe taps over objects and light detects probe displacement

• does not require fixation or staining

• cells are still alive

• probe can damage soft objects

What is electron microscopy and what condition are specimen in during electron microscopy?

• uses a beam of electrons with a very short wavelength

• allows very high resolution

• dead and stained

What is electron cryotomography?

• samples frozen in ice

• take TEM pictures and tilt the stage

• 3D reconstruction

• cells are alive