A Tour of the Cell

Page
2

specimen)

TECHNIQUE

RESULTS

50 µm

Slide 10

Fig. 6-3cd

(c) Phase-contrast

(d) Differential-interference-

contrast (Nomarski)

TECHNIQUE

RESULTS

Slide 11

Fig. 6-3e

(e) Fluorescence

TECHNIQUE

RESULTS

50 µm

Slide 12

Fig. 6-3f

(f) Confocal

TECHNIQUE

RESULTS

50 µm

Slide 13

Two basic types of electron microscopes (EMs) are used to study subcellular structures

Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3-D

Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen

TEMs are used mainly to study the internal structure of cells

Slide 14

Fig. 6-4

(a) Scanning electron

microscopy (SEM)

TECHNIQUE

RESULTS

(b) Transmission electron

microscopy (TEM)

Cilia

Longitudinal

section of

cilium

Cross section

of cilium

1 µm

1 µm

Slide 15

Cell Fractionation

Cell fractionation takes cells apart and separates the major organelles from one another

Ultracentrifuges fractionate cells into their component parts

Cell fractionation enables scientists to determine the functions of organelles

Biochemistry and cytology help correlate cell function with structure

Slide 16

Fig. 6-5

Homogenization

TECHNIQUE

Homogenate

Tissue

cells

1,000 g

(1,000 times the

force of gravity)

10 min

Differential centrifugation

Supernatant poured

into next tube

20,000 g

20 min

80,000 g

60 min

Pellet rich in

nuclei and

cellular debris

Pellet rich in

mitochondria

(and chloro-

plasts if cells

are from a plant)

Pellet rich in

“microsomes”

(pieces of plasma

membranes and

cells’ internal

membranes)

150,000 g

3 hr

Pellet rich in

ribosomes

Slide 17

Fig. 6-5a

Homogenization

Homogenate

Differential centrifugation

Tissue

cells

TECHNIQUE

Slide 18

Fig. 6-5b

1,000 g

(1,000 times the force of gravity)

10 min

Supernatant poured into next tube