2.1.1 Flashcards
Define magnification
how much bigger a sample appears to be under a microscope than it is in real life
Define resolution
The ability to distinguish between two points (level of detail)
Equation for total magnification
objective mag x eyepiece mag
What magnification is a light microscope limited to?
1500x
Difference between how a light microscope works and how an electron microscope works
Light microscope exposes specimen to light, electron microscope exposes it to electrons
What are the two types of electron micropscope?
- Scanning (SEM)
- Transmission (TEM)
Why can electron microscopes have a greater resolution than light microscopes?
Electrons have a shorter wavelength than light
Definition of “plane of view”
the side you see
How are specimens prepared in a scanning electron microscope?
Specimens coated with a layer of metal
Why are specimens covered in a layer of metal pre-viewing?(Scanning EM)
To improve conductivity and contrast
Why must specimens be dead to be viewed under an electron microscope?
Specimens are put in vacuum where they’d die anyway
Do SEMs produce a 2d or a 3d image?
3D
SEMs allow ______ cells/organisms to be scanned
whole
How is a TEM specimen prepared?
Very thinly sliced and coated in a heavy metal
Does a TEM produce a 3d or a 2d image?
2d
How does a TEM work on a prepared specimen?
Fires electrons which don’t pass through the heavily stained parts.
Electrons that pass through are focused by electromagnets onto a fluorescent screen
Name the 4 slide preparation methods
Dry Mount
Wet Mount
Squash slide
Smear
What are dry mount slides useful to look at
whole, solid specimens such as hair, insect and pollen
How are dry mount slides prepared?
specimen placed on center of slide then cover slip is placed over sample
What are wet mount slides useful to look at?
Living or wet samples such as pond water or bacteria
How is a wet mount slide prepared?
small drop of liquid placed on slide
place specimen on top
slowly tilt and lower cover slip, to ensure no bubbles
What are squash slides useful to look at?
soft samples such as plant roots or onion
How is a squash slide prepared?
wet mount prepared first
lens tissue used to gently press down on cover slip
What are smear slides useful to look at?
blood samples
how is a smear slide prepared?
edge of slide used to smear the sample (slide at 45 angle), creating an even, thin layer
cover slip placed on sample
What is an artefact?
A visible structural detail not a feature of the object usually obtained during the making of the slide
Why is staining slides useful?
Allows us to see transparent/hard to see cells
What is differential staining?
Using stains which bind to specific cell structures, meaning each structure can be stained differently and easily identified
3 examples of differential stains
- methylene blue: stains nuclear material
- iodine: stains starch (cell walls)
- gram staining: stains bacteria cell walls
How can gram staining help classify bacteria?
It is either gram negative or gram positive. bacteria can be further classified using other stains
Magnification using sizes equation
Magnification = image size / actual size
What is an eye piece graticule?
A fine scale that fits inside the eyepiece lens. Units are arbitrary
What is a stage micrometer?
A scale fitted onto a coverslip, where the units are known
Is the scale on a stage micrometer known or unknown?
Known
How can we find the value for the units of an eyepiece graticule using a stage micrometer?
Align the two scales and use the known unit to work out the unknown
What is cytosol?
The liquid component of cytoplasm
What are the 4 parts of the nucleus?
- nuclear envelope
- nuclear pore
- chromatin
- nucleolus
What are chromatin?
substance consisting of DNA and proteins
What are nuclear envelopes?
double membranes around edge of nucleus
What is the nucleolus?
Dense regions of DNA, RNA and proteins where ribosomes are synthesized
What is the function of a nucleus?
Controls cell functions
Controls gene expression, protein synthesis and storing DNA
How does the nucleus control cell functions?
DNA transcription
The mitochondria has _ membranes
2, an inner and an outer membrane
How is a mitochondrion’s inner membrane structured?
Folded with high surface area
What is a mitochondrion’s inner membrane called?
Cristae
Why does mitochondria have their own DNA?
To synthesize specific enzymes
What is the function of mitochondria?
Aerobic respiration
Where does anaerobic respiration occur?
Cytoplasm
What is a permanent cell vacuole’s membrane called?
tonoplast
What does the permanent cell vacuole contain?
Cell Sap
What are the functions of a permanent cell vacuole?
- Stores cell sap
- maintains osmotic pressure within the cell
Chloroplasts have a ______ membrane
double
What are stacks of thylakoids in chloroplasts called?
Grana
What are the stoma sacs in chloroplasts called?
Thylakoids
How are grana linked together in chloroplasts?
By pieces of membrane called lamellae
What is the function of chloroplasts?
Photosynthesis
What is the Golgi complex made up of?
Golgi apparatus and small vesicles
What is the structure of the Golgi complex?
Membrane - bound, fluid filled, channel like structure
What are vesicles?
Detached, fluid filled pockets
What is the purpose of the Golgi complex?
- Processes and packages proteins and lipids e.g glycoproteins
- Proteins and lipids stored in vesicles can be transported out through the cell membrane
What is the lysosome?
A type of vesicle containing enzymes such as lysozyme
What is the function of the lysosome?
To digest/break down invading cells, old parts of cells and complex biomolecules
What is the rough endoplasmic reticulum?
A network of channel like structures filled with fluid
What is the difference between Rough ER and smooth ER
Rough has ribosomes along the surface
Why does the rough ER have a large surface area and ribosomes along the surface?
For protein synthesis
What is the purpose of the rough endoplasmic reticulum
protein synthesis
