2.1 Basic components of living Flashcards
What are the 2 lenses called on a compound light microscope?
Objective lens and eyepiece lens
What are the 4 types of sample preparation?
Dry mount
Wet mount
Squash slides
Smear slides
Name 2 positively charged dyes and what they are attracted to
Methylene blue and Crystal violet
attracted to negatively charged materials in the cytoplasm
Name 2 negatively charged dyes and what they are repelled by
Nigrosine and Congo red
repelled by the negatively charged cytosol
What happens to gram positive bacteria when stained with crystal violet?
The gram positive bacteria retain the pain and appear blue/purple under a microscope
What happens to gram negative bacteria when stained with crystal violet?
Gram negative bacteria lose the stain due to thinner cell walls. They are then stained with a counterstain, safranin dye which makes them appear red.
Which type of bacteria is susceptible to penicillin?
Gram positive - it inhibits the formation of cell walls
What are the 4 stages in the production of pre-prepared slides?
- Fixing
- Sectioning
- Staining
- Mounting
What are the rules for producing good scientific drawings?
- include a title
- state magnification
- use a sharp pencil
- use white unlined paper
- use as much paper as possible
- draw smooth continuous lines
- do not shade
- label lines should not cross and should be parallel to the top of the page and drawn with a ruler
How is magnification calculated?
Magnification (no units) = size of image/actual size
What is magnification?
How many times larger the image is than the actual size of the object being viewed
What is resolution?
the shortest distance between 2 objects that can be seen as separate objects
What is resolution limited by?
Diffraction
What is diffraction?
Diffraction is the tendency of light waves to spread as they pass close to physical structures
How can resolution be increased?
by using beams of electrons
What do you use to calibrate a light microscope?
an eyepiece graticule
Name 4 disadvantages of electron microscopy
- expensive
- can only be used inside a carefully controlled environment in a dedicated space
- specimens can be damaged by the electron beam
- problem with artefacts
What are the 2 types of electron microscope?
- Transmission electron microscope
- Scanning electron microscope
What is the difference between TEM and SEM?
In TEM a beam of electrons is transmitted through a specimen whereas in SEM a beam of electrons is sent across the surface of the specimen
How is a sample prepared for electron microscopes?
fixation using chemicals/freezing
staining with heavy metals
dehydration with solvents
Name 4 differences between light microscopes and electron microscopes
- light microscopes are inexpensive to buy and operate
- electron microscopes are large and need to be installed
- electron microscopes require complex sample preparation
- in light microscopy samples can be living or dead
What is an artefact?
A visible structural detail caused by processing the specimen and not a feature of the specimen
How does a laser scanning confocal microscope work?
It moves a single spot of focused light across a specimen which causes fluorescence from components labelled with a fluorescent dye. This emitted light is filtered through a pinhole aperture and is detected. A 2D image is produced.
Name a use of laser scanning confocal microscopy
used in the diagnosis of diseases
What is the function of the nucleus?
It contains the coded genetic information in the form of DNA
What is the function of the nucleolus?
responsible for producing ribosomes. It is composed of proteins and RNA.
What is the function of mitochondria?
They are the site of the final stages of cellular respiration
What are vesicles?
membranous sacs that have storage and transport roles
What are lysosomes?
Specialised forms of vesicles that contain hydrolytic enzymes, responsible for breaking down waste material in cells
What are the 2 important roles of lysosomes?
- in the immune system they break down pathogens
- in programmed cell death/apoptosis
What is the function of the cytoskeleton?
A network of fibres necessary for the shape and stability of a cell
What are the 3 components of the cytoskeleton?
- Microfilaments
- Microtubules
- Intermediate fibres
What are centrioles?
component of the cytoskeleton composed of microtubules involved in the positioning of flagella/cilia and form the centrosome which is involved in the assembly and organisation of the spindle fibres during cell division
What are flagella?
whip like extensions that enable cell’s motility
What are cilia?
hair like extensions that can be mobile or stationary and can move fluids/objects adjacent to cells
What is the endoplasmic reticulum?
a network of membranes enclosing cisternae
What are the 2 types of endoplasmic reticulum and their functions?
- Smooth ER - lipid and carb synthesis and storage
- Rough ER - synthesis and transport of proteins
What are ribosomes?
site of protein synthesis
What is the Golgi apparatus?
compact structure formed of cisternae, does not contain ribosomes and has a role in modifying and ‘packaging’ proteins into vesicles.
What is the function of the cell wall?
gives the plant cell shape and acts as a defence mechanism
What are plant cell walls made of?
Cellulose
What are vacuoles?
membrane lined sacs in the cytoplasm containing cell sap, they are important in the maintenance of turgor
What is the membrane of a vacuole called?
tonoplast
What is the function of chloroplasts?
responsible for photosynthesis
Name 4 differences between prokaryotic and eukaryotic cells?
- prokaryotic cells do not have a nucleus
- prokaryotic DNA is circular
- non-membrane bound organelles in prokaryotic cells
- smaller ribosomes (70S) in prokaryotic cells
