Microscopy

Question 1

List the three points in Cell Theory

Answer 1

*All organisms are composed of one or more cells
*Cells are the basic unit of structure/ organisation in organisms.
*All cells come from Pre-exisitng cells.

Question 2

In the Timeline of cell Theory how did Zacharias Jansen contribute and when?

Answer 2

1600s, Made the first microscope.

Question 3

Who did Jansen send his discoveries to in 1666 and how did they contribute?

Answer 3

Robert Hooke, who came up with the cell after looking at dead plant tissue.

Question 4

How did the word cell develop?

Answer 4

Robert Hooke, looked at a cork under a microscope, observed that they looked like ‘cells’ after the rooms monks slept in in monasteries.

Question 5

In 1674, by who and how was a contribution to cell theory made?

Answer 5

*Anton Van Leeuwenhoek
*Observed first living cells by observing bacteria in his mouth

Question 6

In 1833, who was the first the describe the nucleus?

Answer 6

Robert Brown.

Question 7

In 1837-1838 what were the names of the two German scientists that contributed to cell theory?

Answer 7

*Matthias Schleiden
*Theodore Schwann

Question 8

How and when did Matthias Schleiden and Theodore Schwann contribute to cell theory?

Answer 8

*1837-1838
*Matthias Schleiden- studied plant cells, all plant cells are composed of cells
*Theodore Schwann- studied animals, all living things are composed of cells

Question 9

What discovery did Robert Remark make in 1844?

Answer 9

*By observing cell division, all cells come from pre-exsisting cells.

Question 10

By who and when was Robert Remarks work stolen and republished?

Answer 10

By Rudolph Virchow in 1855

Question 11

By who when and how was the theory of spontaneous generation of cells disproved?

Answer 11

*Louis Pasteur, 1860
*Bacteria only grows in sterile nutrient broth AFTER exposed to oxygen.

Question 12

List the dates in the cell theory timeline

Answer 12

*1660s
*1666
*1674
*1833
*1837-1838
*1844/1855
1860

Question 13

How to work out a compound microscopes total magnification?

Answer 13

Objective lens x Eyepiece lens

Question 14

State how to set up a Light microscope.

Answer 14

1.)Move stage down using coarse adjustment knob.
2.) Set revolving nosepiece to the lowest objective lens
3.) Move the stage all the way up and slowly move down whist observing till roughly in focus.
4.) Adjust fine adjustment knob till focused.

Question 15

List the four types of sample prep.

Answer 15

*Dry Mount
*Wet Mouth
*Squash slides
*Smear slides

Question 16

Describe a Dry Mount

Answer 16

Specimen viewed alone without any liquid medium. e.g Hair

Question 17

Describe a Wet Mount

Answer 17

Specimens viewed with a liquid medium, coverslip is placed at an angle. e.g living organisms.’Normal’

Question 18

Describe a Squash slide

Answer 18

Wet mount prepared, and squashed down with lens tissue. Reduces thickness.

Question 19

Describe a Smear Slide.

Answer 19

Drop of sample smeared with the slip at 45*, thin even coat. E.g blood.

Question 20

Name the four Production of slides.

Answer 20

*Fixing
*Sectioning
*Staining
*Mounting

Question 21

Describe the process of Fixing

Answer 21

Using chemicals e.g formaldehyde to preserve specimens.

Question 22

Describe the process of Sectioning

Answer 22

Specimen dehydrated with alcohols, put in wax resin & cut thinly with a microtome (knife)

Question 23

Describe the process of Staining

Answer 23

Colour, sometimes multiple, to highlight organelles as they are often transparent, or provide contrast

Question 24

Describe the process of Mounting

Answer 24

Securing on slide with a coverslip

Question 25

What occurs before the process of staining.

Answer 25

Placed on a slide to air dry, then heated through flame.

Question 26

What dyes are negatively charged

Answer 26

Nigrosin, Congo red

Question 27

What dyes are positively charged

Answer 27

Crystal violet, Methylene blue.

Question 28

What is the negative staining technique?

Answer 28

* the + stain stains - components of cells. e.g Crystal violet *- charge stains are repelled with the cell, stain outside for contrast.

Question 29

What is differential staining?

Answer 29

Using multiple dyes

Question 30

What is Gram stain technique?

Answer 30

*A type of differential staining. *Seperates bacteria into gram positive and gram negative. *1.)Crystal violet applied to specimen on slide, then iodine to fix (a trapping reagent) 2.)Washed with alcohol. 3.) Gram positive takes the crystal violet stain. 4.) Gram negative= thinner cell walls, the stain + outer membrane washed away. 5.) Counterstain, safranin dye added to the negative.

Question 31

What is Acid-fast technique?

Answer 31

*A type of differential staining. *Differentiates species of Mycobacterium from other bac. *1.)Lipid solvent carries carbolfuchsin dye to cells. 2.) Specimen washed with dilute acid. 3.) Mycobacterium not affected by acid, stays stained red. 4.) Other bac loses the stain and is counterstained Methylene blue.

Question 32

What are the rules of scientific drawings?

Answer 32

Title, stated Mag, labels (components), state colours + shapes, solid lines, no shading, label lines straight with no arrow heads, accurate proportions, all off to one side.

Question 33

State the definition of magnification.

Answer 33

How many x larger the image is to the actual object.

Question 34

State the definition of Resolution

Answer 34

The ability to see two objects as seperate

Question 35

What is the magnification calculation

Answer 35

Size of image = magnification x actual size

Question 36

What is the order (largest to smallest) of the smaller units you need to know?

Answer 36

Millimeters (mm) Micrometers (μm) Nanometers (nm) Picometers (pm)

Question 37

Why does the electron microscope have a higher resolution?

Answer 37

Electrons have a shorter wavelength than light.

Question 38

What is the difference between the Eye piece Graticule and Stage micrometer?

Answer 38

Eye piece Graticule- In microscope Stage micrometer- Added to the slide. Exactly 1 mm long

Question 39

Explain how to calibrate an eye piece micrometer (finding out how much one division is worth)

Answer 39

1.)Aline the Eye piece graticule with the stage micrometer 2.) Check the size of your micrometer. if 1mm, every 10 divisions is 0.1 mm, every 1 is 0.01. 3.) Divide the known value of the stage micrometer by small divisions of the eye peice graticule that fit inside. e.g 10 divisions= 0.1mm/ e.g 20 (divisions) 4.) Convert to correct units.

Question 40

State the advantages of using a light microscope

Answer 40

*Can use Living samples *Colour image produced, *Inexpensive £150, *Small/portable *Simple sample prep *reduced distortion *No vacuum required

Question 41

State the Disadvantages of using a Light microscope

Answer 41

*Poorest resolution- less detail *Only up to x2000 mag- less organelles visible *Resolving power of 200nm

Question 42

State the advantages of using a electron microscope

Answer 42

*Over 500,000x mag *Low resolving power

Question 43

State the disadvantages of using a electron microscope

Answer 43

*Expensive buy/ operate *Vaccum needed *Large *Needs installing *Complex sample prep *Often distorts *Only black and white images *Only dead specimens

Question 44

Why do Electron microscopes need to be in a vacum?

Answer 44

Ensures electron beams travel in straight lines.

Question 45

Describe how a transmission electron microscope works

Answer 45

Electrons are transmitted through thin specimens, thinker parts get absorbed and are darker. Has the highest magnification, resolving power of 0.5nm

Question 46

Describe how a Scanning electron microscope works and state resolving power

Answer 46

Electrons bounce of specimens surface, giving a 3D image. Specimen doesn’t need to be thin. Have aResolving power of 3-10nm.

Question 47

How do you convert cm to mm

Answer 47

1cm =10mm

Question 48

How many cm in 1m

Answer 48

100 cm