lecture 1

Question 1

Scientific method

Answer 1

1. observation
   2.formulate a testable hypothesis
   3.design a controlled experiment
2. collect data
   5.interpret results
   6.accept or reject the hypothesis

between 1-2 and 5-6 is consult prior knowledge
3-4 may have to go back and redesign experiment

Question 2

the cell theory

Answer 2

-all organisms consist of one or more cells
-the cell is the basic unit of structure for all organisms
-all cells arise only from preexisting cells
(ominis cellula e cellula-1855 Rudolf Virchow)

Question 3

deci (d)

Answer 3

10-1

Question 4

centi (c)

Answer 4

10-2

Question 5

milli (m)

Answer 5

10-3

Question 6

micro (um)

Answer 6

10-6

Question 7

nano (n)

Answer 7

10-9

Question 8

what organisms can be seen with the electron microscope?

Answer 8

atoms
small molecules
dna, proteins, lipids
ribosomes
viruses
mitochondrion
most bacteria
nucleus

Question 9

what organisms can be seen with the light microscope?

Answer 9

mitochondrion
most bacteria
nucleus

Question 10

light microscope

Answer 10

an instrument that uses light magnifying lenses and an eyepiece to examine objects too small to be seen by the naked eye

-allows identifying membrane-bounded structures (nuclei, mitochondria, chloroplasts

Question 11

limitation of light microscopy

Answer 11

1. only dark objects can be seen well (dense)- difficult to see living internal structure
   2.resolution is about 0.2 micron (λ/2 is where λ is the light wavelength)-shorter wavelength hsve better resolutiom
2. out of focus light reduces clarity

Question 12

resolution in microscopy

Answer 12

the shortest distance between two points on a specimen that can be still be distinguished by the observer or camera system as separate entities.

-if the limit of resolution is 400nm, objects must be at least 400nm apart to be recognized as separate entities

-the smaller the l.o.r, the greater the resolving power(the ability to see fine details

Question 13

brightfield microscopy

Answer 13

-unstained: passes light directly through the specimen, unless cell is naturally pigmented or artificially stained, image has little contrast

-stained: staining w various dyes enhances contrast, but most staining procedures requires that cells be fixed (preserved)

Question 14

phase contrast

Answer 14

+make it possible to see living cells clearly
enhances contrast in unstained cells by amplifying variations in refractive index within specimen (playing w properties of light)
*useful for examining living unpigmented cells

Question 15

differential interference contrast

Answer 15

+make it possible to see living cells clearly
uses optical modifications to exaggerate differences in refractive index (played w properties of light)

Question 16

Fluorescence

Answer 16

_shows the locations of specific molecules
_absorb uv (energy is higher, short wavelength) & emit visible light( energy is lower, long wavelength)
_often tag molecules of interest with fluorescent dye/ antibodies
*positively charged dye will bind to negatively charged cell

Question 17

confocal

Answer 17

USES LASER and special optics to focus illuminating beam on a single plane within the specimen
-only the specific region is imaged (above/ below the region will appear black)

Question 18

electron microscope: when, where, who

Answer 18

-1913
-germany
-by max knoll & ernst ruska

Question 19

what is an electron microscope?

Answer 19

_uses a beam of electrons that is deflected & focused by an electromagnetic field
_allows small organelles to be seen (ribosomes, cell membranes, microtubules, microfilaments
_allow macromolecules to be seen (DNA & proteins)
-resolution: 0.2-0.5 nm (1000x more than a light microscope)

-treat w heavy metals
-can only see thru dead cells

Question 20

two designs of electron microscope

Answer 20

1. transmission electron microscope (TEM)
2. scanning electron microscope (SEM)

Question 21

transmission em

Answer 21

forms an image from electrons that are transmitted thru the specimen

Question 22

scanning em

Answer 22

scans SURFACE of the specimen(heavy metals binds to the surface)
-resolution is limited by the width of the beam

Question 23

where did the 3 types of cells evolve from

Answer 23

ancestral cells

Question 24

3 types of cells

Answer 24

1. bacteria (prokaryotes)
2. archaea (prokaryotes): “extremophiles”-live in extreme climates and conditions
3. eukarya

Question 25

what do bacteria have

Answer 25

contain mostly DNA
no membrane organelles
no nuclear envelope

Question 26

organelles of plant cells

Answer 26

-shape: fixed (rectangular)
-rarely have cilia, flagella
- chloroplasts & plastids
-cell wall
-one large vacuole
-centrioles (only in lower plants)

Question 27

organelles of animal cells

Answer 27

shape: round/irregular (can change)
-cilia and flagella
-lysosomes (digestive enzymes)
-few small vacuoles
centrioles ( microtubules that organizes the miotic spindle)