2.1.2 PK Cell & 2.1.3 Methods Of Studying Cells

Question 1

What is a prokaryotic cell?

Answer 1

A cell without a nucleus

They are smaller

Question 2

What is in a bacterial cell that isn’t in a normal eukaryotic cell?

Answer 2

Plasmid
Genetic DNA
Flagellum
Slime capsule

Question 3

What is the function of a slime capsule?

Answer 3

Protects the bacterial cell

Allows the cell to adhere to smooth surfaces

Question 4

What is the function of the flagellum?

Answer 4

Uses a propeller like motion to move

A sensory organelle - sensitive to chemical and temperature

Question 5

What is the cell wall made from in a bacterial cell?

Answer 5

Peptidoglycan / murein

Question 6

What are common features of a virus?

Answer 6

Protein coat/ capsid
Genetic material
Glycoproteins

Question 7

What is the function of the capsid/protein coat?

Answer 7

Protects the nucleic acid from being digested by enzymes

Provides site and proteins on the surface to allow viron penetration

Question 8

What is the role of viral attachment proteins?

Answer 8

Binds to cell membranes, to then allow the DNA to be inserted into the cell

Question 9

What is the size of a prokaryotic ribosome?

Answer 9

70S

Question 10

What are the types of microscopes?

Answer 10

Light/Optical
Scanning Electron
Transmission Electron

Question 11

How does a light/optical microscope work?

Answer 11

Uses visible light and magnifying lens to enlarge them
Can only see organelles larger than 0.2 μm
Can magnify up to 2000x

Question 12

What is resolution?

Answer 12

The minimum distance apart that two objects can be distinguished as separate objects in an image

Question 13

What are the advantages of light/optical microscope?

Answer 13

Cheap
Living samples can be viewed
Preparation is quick
Unaffected by magnetic fields 
No vacuum required

Question 14

What are the disadvantages of light/optical microscope?

Answer 14

Poor resolution
Only magnifies up to 2000x
Preparation may distort specimen

Question 15

How does a scanning electron microscope work?

Answer 15

It scans the surface with a broad static beam of electrons producing various signals containing information about the topography (shape and features of the surface)

Done in a vacuum chamber

Question 16

What are the advantages of using a scanning electron microscope?

Answer 16

Easy to use
Sample can be seen as a 3D image
Fairly high resolution
Works fast

Question 17

What are the disadvantages of a scanning electron microscope?

Answer 17

Specimen must be conductive
Preparation could produce artefacts
Images are black and white
Living specimens can’t be observed as it is done in a vacuum

Question 18

How does a transmission electron microscope work?

Answer 18

A focused beam of electrons, using electromagnetic lenses, travels through a vacuum to the sample
Parts of the specimen absorb the electrons and appear darker

Question 19

What are the advantages of transmission electron microscope?

Answer 19

Very powerful magnification
Images are high quality/resolution
Provides information on element and compound structure

Question 20

What are the disadvantages of transmission electron microscope?

Answer 20

High energy beam may destroy the sample
Living specimens can’t be observed as it is done in a vacuum
Potential for artefacts
Complex staining process and images are still in black and white

Question 21

Conversions of: 
Millimetres
Micrometers 
Nanometers
Picometres 

From meters

Answer 21

10 ^-3
10 ^-6
10 ^-9
10 ^-12

Question 22

What is the equation for magnification?

Answer 22

IAM
I / A x M

I am an iams cat😅

Question 23

What is actual size?

Answer 23

What is would be in real life

Quite little in micrometers

Question 24

What is image size?

Answer 24

Whatever you can see in front of you

Question 25

How do you prepare a temporary mount microscope slide?

Answer 25

Use forceps to handle the sample
Smooth out air bubbles/creases
Add a stain to colour the sample
Add a little water to stick the glass together

Question 26

What is cell fractionation?

Answer 26

The process of separating different organelles of a cell

Question 27

What happens in cell fractionation?

Answer 27

The tissue is cut up and put in a cold, isotonic, buffered solution
Further broken up in a homogeniser forming homogenate
The homogenate is spun in a ultracentrifuge at a low speed for 10mins to force the heaviest organelles to the bottom
The supernatant is transferred to another tube and spun at a higher speed
This is repeated

Question 28

Why is a cold solution used in cell fractionation?

Answer 28

To stops enzymes working effectively

Question 29

Why is an isotonic solution used in cell fractionation?

Answer 29

Keeping the concentrations the same prevents osmosis which stops cells bursting

Question 30

Why is a buffered solution used in cell fractionation?

Answer 30

Keeps the pH the same

Question 31

What is a homogeniser?

Answer 31

Like a blender

To break up the cell wall and the cell membrane

Question 32

What is the supernatant?

Answer 32

The liquid left above the solid organelles in a test tube after centrifugation

Question 33

What are the heaviest to lighter organelles?

Answer 33

Nucleus 
Mitochondria
Lysosomes 
Endoplasmic reticulum 
Ribosomes

Question 34

How can we measure the size of objects using a light microscope?

Answer 34

Using an eyepiece graticule

This is a glass disk placed on the eyepiece of the microscope with a scale etched on

Question 35

How do you calibrate an eyepiece graticule?

Answer 35

You use a stage micrometer to line it up and work out the scale