A Tour of the Cell

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Slide 1

The Fundamental Units of Life

All organisms are made of cells

The cell is the simplest collection of matter that can live

Cell structure is correlated to cellular function

All cells are related by their descent from earlier cells

Slide 2

Fig. 6-1

Slide 3

Concept 6.1: To study cells, biologists use microscopes and the tools of biochemistry

Though usually too small to be seen by the unaided eye, cells can be complex

Slide 4

Microscopy

Scientists use microscopes to visualize cells too small to see with the naked eye

In a light microscope (LM), visible light passes through a specimen and then through glass lenses, which magnify the image

Slide 5

The quality of an image depends on

Magnification, the ratio of an object’s image size to its real size

Resolution, the measure of the clarity of the image, or the minimum distance of two distinguishable points

Contrast, visible differences in parts of the sample

Slide 6

Fig. 6-2

10 m

1 m

0.1 m

1 cm

1 mm

100 µm

10 µm

1 µm

100 nm

10 nm

1 nm

0.1 nm

Atoms

Small molecules

Lipids

Proteins

Ribosomes

Viruses

Smallest bacteria

Mitochondrion

Nucleus

Most bacteria

Most plant and animal cells

Frog egg

Chicken egg

Length of some nerve and muscle cells

Human height

Unaided eye

Light microscope

Electron microscope

Slide 7

LMs can magnify effectively to about 1,000 times the size of the actual specimen

Various techniques enhance contrast and enable cell components to be stained or labeled

Most subcellular structures, including organelles (membrane-enclosed compartments), are too small to be resolved by an LM

Slide 8

Fig. 6-3

TECHNIQUE

RESULTS

(a) Brightfield (unstained

specimen)

(b) Brightfield (stained

specimen)

50 µm

(c) Phase-contrast

(d) Differential-interference-

contrast (Nomarski)

(e) Fluorescence

(f) Confocal

50 µm

50 µm

Slide 9

Fig. 6-3ab

(a) Brightfield (unstained

specimen)

(b) Brightfield (stained