2.1.2 PK Cell & 2.1.3 Methods Of Studying Cells Flashcards
What is a prokaryotic cell?
A cell without a nucleus
They are smaller
What is in a bacterial cell that isn’t in a normal eukaryotic cell?
Plasmid
Genetic DNA
Flagellum
Slime capsule
What is the function of a slime capsule?
Protects the bacterial cell
Allows the cell to adhere to smooth surfaces
What is the function of the flagellum?
Uses a propeller like motion to move
A sensory organelle - sensitive to chemical and temperature
What is the cell wall made from in a bacterial cell?
Peptidoglycan / murein
What are common features of a virus?
Protein coat/ capsid
Genetic material
Glycoproteins
What is the function of the capsid/protein coat?
Protects the nucleic acid from being digested by enzymes
Provides site and proteins on the surface to allow viron penetration
What is the role of viral attachment proteins?
Binds to cell membranes, to then allow the DNA to be inserted into the cell
What is the size of a prokaryotic ribosome?
70S
What are the types of microscopes?
Light/Optical
Scanning Electron
Transmission Electron
How does a light/optical microscope work?
Uses visible light and magnifying lens to enlarge them
Can only see organelles larger than 0.2 μm
Can magnify up to 2000x
What is resolution?
The minimum distance apart that two objects can be distinguished as separate objects in an image
What are the advantages of light/optical microscope?
Cheap Living samples can be viewed Preparation is quick Unaffected by magnetic fields No vacuum required
What are the disadvantages of light/optical microscope?
Poor resolution
Only magnifies up to 2000x
Preparation may distort specimen
How does a scanning electron microscope work?
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
What are the advantages of using a scanning electron microscope?
Easy to use
Sample can be seen as a 3D image
Fairly high resolution
Works fast
What are the disadvantages of a scanning electron microscope?
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
How does a transmission electron microscope work?
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
What are the advantages of transmission electron microscope?
Very powerful magnification
Images are high quality/resolution
Provides information on element and compound structure
What are the disadvantages of transmission electron microscope?
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
Conversions of: Millimetres Micrometers Nanometers Picometres
From meters
10 ^-3
10 ^-6
10 ^-9
10 ^-12
What is the equation for magnification?
IAM
I / A x M
I am an iams cat😅
What is actual size?
What is would be in real life
Quite little in micrometers
What is image size?
Whatever you can see in front of you
How do you prepare a temporary mount microscope slide?
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
What is cell fractionation?
The process of separating different organelles of a cell
What happens in cell fractionation?
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
Why is a cold solution used in cell fractionation?
To stops enzymes working effectively
Why is an isotonic solution used in cell fractionation?
Keeping the concentrations the same prevents osmosis which stops cells bursting
Why is a buffered solution used in cell fractionation?
Keeps the pH the same
What is a homogeniser?
Like a blender
To break up the cell wall and the cell membrane
What is the supernatant?
The liquid left above the solid organelles in a test tube after centrifugation
What are the heaviest to lighter organelles?
Nucleus Mitochondria Lysosomes Endoplasmic reticulum Ribosomes
How can we measure the size of objects using a light microscope?
Using an eyepiece graticule
This is a glass disk placed on the eyepiece of the microscope with a scale etched on
How do you calibrate an eyepiece graticule?
You use a stage micrometer to line it up and work out the scale
