Unit 1: Microscopy

Question 1

What is Microscopy?

Answer 1

Ratio of image size to object size

Question 2

What is Resolution?

Answer 2

The ability of distinguish between 2 objects that are close together

Question 3

Magnification Formula

Answer 3

Magnification (M) = Image size (I) ÷ Actual size (A)

Question 4

What are the 4 types of microscopes?

Answer 4

Light, Scanning Electron (SEM), Transmission Electron (TEM) and Laser Scanning Confocal

Question 5

Light Microscope Facts

Answer 5

Magnification 1000-2000x, Resolution 50-200nm and used for viewing tissues and cells

Question 6

Scanning Electron Microscope (SEM) Facts

Answer 6

Magnification 50000-500000x, Resolution 0.4-20nm and used for viewing surfaces of cells and organelles in 3D images

Question 7

Transmission Electron Microscope (TEM) Facts

Answer 7

Magnification 300000-1000000x, Resolution 0.05-1.0nm and used for detailing organelles - ultrastructure

Question 8

Laser Scanning Confocal Microscope Facts

Answer 8

Magnification 1000-2000x, Resolution 50-200nm and used to provide 3D images with good depth selection

Question 9

Advantages and Disadvantages of LM

Answer 9

+ Cheap and easy to use
+ Allows us to see living things
- Limited resolution

Question 10

Advantages and Disadvantages of SEM & TEM

Answer 10

+ Better resolution than LM and therefore clearer, more detailed images
+ SEM is 3D and is good for viewing surfaces
- Very large and expensive which require trained operatives
- Cannot view living organisms
- Images are black and white (colour added through false colour electron micrographs)

Question 11

Advantages and Disadvantages of LSCM

Answer 11

+ Specimens can be living
+ Can be focused at specific depths
- Relies on computers to create image, which is made from dots of light created by lasers - the image is more of an interpretation

Question 12

What is staining?

Answer 12

Application of coloured stains to the tissues or cells

Question 13

What is the purpose of staining?

Answer 13

Most cell components are colourless and hard to see, therefore staining makes them visible under LM, increases the contrast between organelles and is often specific to each tissue or organelle

Question 14

Examples of stains

Answer 14

Acetic Orcein: Chromosomes - Dark red
Eosin: Cytoplasm
Sudan Red: Lipids
Iodine (from Potassium Iodide): Cellulose - Yellow, Starch Grains - Blue/Black

In an electron microscope, stains are typically heavy metals that reflect/absorb electrons

Question 15

What are cells?

Answer 15

The basic component of living organisms

Question 16

Cell wall

Answer 16

Cellulose cell wall surround plant cells

Question 17

Centrioles

Answer 17

1. Involved in the organisation of the microtubules that make up the cytoskeleton
2. Form spindle fibres to move chromosomes in nuclear division

Question 18

Chloroplasts

Answer 18

Site of photosynthesis

Question 19

Cilia

Answer 19

1. Small hair-like extensions of cell surface membrane containing microtubules
2. Large numbers work in synchronised fashion
3. Able to move whole organisms or to move fluid (mucus) across a surface

Question 20

Cytoskeleton

Answer 20

1. Network of microtubules and microfilaments
2. Provides mechanical strength, support and structure for the cell
3. Maintains the cell shape and is used in some cells to change the shape of the cell
4. Enables movement of organelles inside the cell
5. Enables movement of the whole cell

Question 21

Flagella

Answer 21

1. Large extension of cell-surface membrane containing microtubules (in eukaryotes)
2. Able to beat to enable locomotion or move fluids

Question 22

Golgi apparatus

Answer 22

1. Modifies proteins made in the ribosomes
2. Often adds a carbohydrate group
3. Repackages proteins into vesicles for secretion

Question 23

Lysosomes

Answer 23

Small vacuoles containing hydrolytic or lytic enzymes

Question 24

Mitochondria

Answer 24

Site of aerobic respiration

Question 25

Nucleus, Nucleolus and Nuclear Envelope

Answer 25

1. Contains the genetic material (chromosomes)
2. Controls the cell activities
3. The nuclear envelope separates the genetic material from the cytoplasm
4. The nuclear pores allow molecules of mRNA to pass from the nucleus to the ribosomes in the cytoplasm
5. The nucleolus assembles the ribosomes

Question 26

Ribosomes

Answer 26

Site of protein synthesis

Question 27

Rough Endoplasmic Reticulum (RER)

Answer 27

1. Holds many of the ribosomes

2. Provides a large surface area for protein synthesis

Question 28

Smooth Endoplasmic Reticulum (SER)

Answer 28

Associated with the synthesis, storage and transport of lipids and carbohydrates

Question 29

Production and Secretion of Proteins

Answer 29

1. mRNA leaves nucleus via nuclear pores
2. It is used by the ribosomes in the RER to construct a protein
3. This protein travel to the golgi in a vesicle
4. The vesicle is moved by the cytoskeleton
5. The golgi modifies the protein, often by adding on a carbohydrate group and repackages it into a vesicle
6. The vesicle is moved into the cell surface (plasma) membrane
7. The vesicle fuses with the membrane to release the protein from the cell

Question 30

Prokaryotic Cells

Answer 30

1. Smaller than eukaryotes - 10um long and 1-2um wide
2. No nucleus
3. No membrane-bound organelles
4. 18nm sized ribosomes
5. Single loop of DNA; no histones
6. Some cells have a flagellum, and generally have a very different structure

Question 31

Eukaryotic Cells

Answer 31

1. Larger than prokaryotes - 10um diameter
2. Has a nucleus
3. Has membrane-bound organelles
4. 22nm sized ribosomes
5. DNA associated with proteins (histones)
6. Some cells have a flagellum with ‘9+2’ structure of microtubules