Lab 2: Cells

Which one of the following substances is not a lipid?

• A) wax • B) cholesterol • C) cellulose • D) steroids • E) triglycerides

You now know that the old cliche "oil and water don't mix" is true. Why?

• A) Oil exhibits polarity and water does not. • B) Water exhibits polarity and oil does not. • C) Oil is hydrophilic. • D) Water is hydrophobic. • E) Oil is an organic compound and water is

not.

A molecule with the formula C55H110O55 is probably a(n)

• A) oil. • B) steroid. • C) wax. • D) protein. • E) polysaccharide.

All living things are made of cells

• Cells are the basic unit of living things

• All cells come from other cells

• This is the classical cell theory

Cells are small

• Most bacteria are .5-2µm in size

• Light microscope’s limit= ~500nm=.5µm

• Single eukaryotic cells are larger, but still to small to see without magnification

Microscopes allow us to see the world of cells

• Microscopes use multiple lenses to magnify small things

Measuring the world of the small• We use the metric system • The metric system uses powers of 10• Major metric prefixes are 1000-fold apart• English-Metric conversions:• 1 meter = 1.09 yards• 1 centimeter = .4 inches• Metric interconversions• 1 m = 100 cm• 1 cm = _____m

The Metric System

• Decimal system (powers of 10)• Base units (meter, gram) modified by prefixes:

kilo = thousand 1000.0centi (c) = hundredthcenti (c) = hundredth 0.010.01milli (m) = thousandthmilli (m) = thousandth 0.0010.001micro (µ) = millionthmicro (µ) = millionth 0.0000010.000001nano (n) = billionthnano (n) = billionth 0.0000000010.000000001

The Metric System

• How do you convert from one metric unit to another?

• Each decimal place represents one power of 10.

• 1.0 meter =100 or 102 centimeters (cm)1000 or 103 millimeters (mm)1,000,000 or 106 micrometers (µm or microns)

1,000,000,000 or 109 nanometers (nm)

The Metric System

• Example: 1.0 cm = ? m– Since a centimeter is a hundredth of a meter, it is

10x10 or 2 decimal places smaller than a meter. – So, move the decimal point 2 places to the left:

1.0 cm = 0.01 m

The Metric System

• Example: 1.0 cm = ? mm– First put both in terms of meters:

1.0 m = 100.0 cm = 1000.0 mm– How many powers of ten (decimal places) are

there between cm and mm? – If 100.0 cm = 1000.0 mm, then

1.0 cm = 10.0 mm – So to convert from cm to mm, you must multiply

by 10 (move the decimal point one place to the rightright).

To convert…A. Meters to centimeters,B. Micrometers to meters,C. Millimeters to micrometers,D. Micrometers to centimeters,…we must…a. multiply by 100. b. divide by ________.c. _________ by ________.d. __________ by ________.

To convert…A. Meters to centimeters,B. Micrometers to meters,C. Millimeters to micrometers,D. Micrometers to centimeters,…we must…a. multiply by 100. b. divide by _1000___.c. _multiply__ by _1000___.d. ____divide by __10,000 .

Using a Light Microscope

1. Get microscope from cabinet• Carry with one hand holding armarm and the other

supporting the basebase

Arm

Base

Using a Light Microscope 1. Ocular (eyepiece)

2. Arm

3. Coarse focus knob

4. Fine focus knob

5. Base

6. Nosepiece

7. Objectives

8. Stage

9. Stage clips

10. Diaphragm

11. Light source

Calculating Magnification

• Ocular lens (10X) x Objective lens

Field of View

• Actual diameter of microscope image at a certain mag.

• As magnification increases, field of view _______.

Using a Light Microscope

• Letter “e”– Practice steps for observing specimens– Draw what you see at different powers– Calculate total magnification

• Silk threads– Get a sense of ‘depth of field’ (how deep can

lenses focus at different powers) – Try to determine relative positions of threads

(top, middle, bottom)

Cells can be placed into two categories

• Prokaryotic and eukaryotic

• Prokaryotic- smaller and simpler

• Eukaryotic- larger and more complex

• Eukaryotic- containing membrane-bound organelles

Observing Cells

• Onion Cells• Cheek cells• Elodea cells• Elodea cells (in salt water)• Pond water

Cell structures- Animal cell

Cell structures- Plant cell

Your instructions for the lab• 1. Draw each subject in detail. Label 2

organelles.• 2. Using field of view, estimate size of

specimens.• 3. On back of paper, compare and contrast:– Onion vs. elodea– Elodea in salt vs. elodea in fresh water– Plant vs. animal cells

• 4. Describe drawn pond water organism. What does it look like? Size? What do you think it is? Categorize it. Unicellular? Plant or animal? Etc.

Using a Light Microscope

• Cleaning up:– Remove and return your slides.– Put the scanning objective in place and lower it all

the way down. – Roll up the lamp cord neatly.– Carefully return your microscope to the shelf

where you got it.

• .