Cells And Microscopy Flashcards
How to complete a dry mount slide?
Solid specimens viewed while or cut into thin slices, sectioning.
Place on centre of slide and place coverslip over the sample
Eg pollen, hair, plant sections
How to wet mount a slide?
Specimen suspended in liquid such as water or immersion oil. Coverslip placed from an angle.
Used for viewing aquatic samples and living organisms.
How to prepare squash slide?
Wet mount prepared first, then Lena tissue is used to gently press down the cover slip
Used for soft samples.
Take care not to damage coverslip when pressing down
How to prepare smear slide?
Edge of slide is used to smear sample creating thin, even coating on another slide, cover slip placed over the sample.
Used for viewing blood.
What is differential staining?
Can distinguish between two types of organisms that would otherwise be hard to identify.
Can also differentiate between different organelles of a single organisms in a tissue sample
What is gram stain technique used for?
Used to separate bacteria into two groups - gram positive and gram negative.
What colour do gram positive bacteria appear under the microscope?
Blue or purple
What colour do gram negative bacteria appear when stained with safranin?
Red
What are the stages of production within slides?
Fixing with chemicals to preserve
Sectioning to form thin slice
Staining for visibility
Mounting on a slide.
What are some rules for a good scientific drawing?
Title
State magnification
Use sharp pencil
Use at least 50% of page
Do not shade
Smooth continuous lines
Clearly defined structures
Label lines should not cross or have arrow heads
What is magnification?
How many times larger the image is than the actual size of the object you’re viewing.
What is resolution?
Ability to see individual objects / structures as separate entities.
What limits resolution?
Diffraction
How can resolution be increased?
By using beams of electrons which have a wavelength thousands of times shorter than light.
Shorter wavelength = beams can be much closer before they overlap
Magnification equation?
Magnification = image / actual
How does electron microscopy work?
Beam of electrons with wavelength of less than 1nm is used to illuminate the specimen.
What can be seen using an electron microscope?
Cell ultrastructure
Up to what magnification can be viewed under electron microscope?
x500 000
What are the 2 types of electron microscope?
Transmission electron microscope
Scanning electron microscope
How does a transmission electron microscope work?
Beak of electrons passed through specimen and focused to produce an image. Has best resolution with resolving power of 0.5nm
How does a scanning electron microscope work?
Beam of electrons passed over the surface of a specimen and reflected electrons are collected.
Resolving power between 3-10nm so not as good
But
3D images of the surface are produced showing us how organisms look.
What is an artefact in microscopy?
A visible structural detail caused by processing the specimen and not a feature of the specimen itself.
What does a laser scanning confocal microscope do?
Moves a single spot of light across a specimen. This causes fluorescence from the components labelled with a dye
How does a confocal microscope work?
Higher light intensity is used to illuminate specimen that has been tested with fluorescent dye. Fluorescence is the absorption and re radiation is light. Light of a longer wavelength and lower energy is emitted and used to produce a magnified image.
What does metabolism involve?
The synthesis and breaking down of different molecules.
What is the function of the nucleus in eukaryotic cells?
Contains coded genetic information in the form of DNA molecules, these DNA molecules direct the synthesis of all proteins required by the cell.
This DNA controls the metabolic activities of the cell
What is the nuclear envelope abs what does it do?
A double membrane that contains DNA to protect the DNA from damage in the cytoplasm.
What do the nuclear pores do?
Allow molecules to move into and out of the cell eg rna molecules leave the nucleus this way
What does the nucleolus do?
It’s responsible for producing ribosomes and it’s made up of proteins and RNA
What is the function of the mitochondria?
They are the site of the final stages of cellular respiration, where the energy is stored in the bonds of complex, organic molecules are made available for the cell to use by the production of ATP
Describe the structure of the mitochondria?
Have a double membrane
Membrane forms internal folds called Cristae
Fluid interior called the matrix
Contains small amount of mitochondrial DNA.
What are vesicles?
Membranous sacs that have storage and transport roles. Single membrane with fluid inside.
Used to transport molecules / materials inside the cell
What are lysosomes?
Specialised forms of vesicles that contain hydrolytic enzymes.
They’re responsible for breaking down waste material in the cell, including old organelles.
Also break down pathogens and involved in apoptosis
What is the cytoskeleton?
Network of fibres necessary for the shape and stability of a cell. Organelles are held in place by the cytoskeleton and it controls all cell movement and the movement of organelles within cells.
What are the 3 components of the cytoskeleton?
Microfilaments
Microtubules
Intermediate fibres
What do microfilaments do?
Formed from actin.
Responsible for cell movement and also cell contraction during cytokinesis.
What do microtubules do?
Formed from globular Tubulin proteins to form tube like scaffold structure which determines cell shape.
Act as tracks for the movement of organelles, including vesicles, around the cell.
Spindle fibres are composed of microtubules.
What do intermediate fibres do?
Give mechanical strength to cells to help to maintain their integrity.
Where would you find centrioles?
Component of cytoskeleton is most eukaryotes with the exception of flowering plants and fungi.
What do centrioles do?
Composed of microtubules. Two associated centrioles form the centrosome which is involved in assembly and organisation of spindle fibres during cell division.
What do flagella do?
Primarily used to enable cell motility. In some cells they’re used as a sensory organelle detecting chemical changes in the cells environment.
What do cilia do?
Can be mobile or stationary.
Stationary cilia found on surface of many cells and have important function in sensory organs such as the nose.
Mobile cilia beat in a rhythmic manner creating a current, and cause fluids or objects adjacent to the cell to move.
What does the SER do?
Responsible for lipid and carbohydrate synthesis and storage
What does the RER do?
Had ribosomes bound to the surface and is responsible for the synthesis and transport of proteins.
What does a ribosome do?
Constructed of RNA molecules made in the nucleolus of the cell. Site if protein synthesis.
What does the Golgi apparatus do?
Compact structure formed of cisternae and does not contain ribosomes.
Modifies proteins and packs them into vesicles
Describe protein production?
Proteins synthesised on ribosomes bound to the endoplasmic reticulum.
These pass into the cisternae and are packaged into transport vesicles
Vesicles containing the newly synthesised proteins move towards the Golgi apparatus via the transport section of the cytoskeleton
Vesicles fuse with the Golgi apparatus and proteins enter. Proteins are structurally modified before leaving the Golgi apparatus in vesicles.
Vesicles move towards CSM releasing their contents by exocytosis.
What are plant cell walls made of?
Cellulose
What is the role of the plant cell wall?
Freely permeable so substances can pass into and out of cell.
Give the cell shape.
Act as a defence mechanism, protects the contents of the cell wall against invasive pathogens.
What is the role of the vacuole?
Important in the maintenance of turgor, to maintain cell rigidity. Tonoplast membrane is selectively permeable
What is the tonoplast?
Membrane of the vacuole, selectively permeable so that some small molecules can pass through but others cannot.
What is the function of a chloroplast?
Organelles responsible for photosynthesis in plant cells. Found in green parts of plants like the leaves.
What is stroma?
Fluid enclosed in the chloroplast where reactions for photosynthesis take place.
Why can chloroplasts makes their own proteins?
Because they contain dna and ribosomes
What does DNA do in prokaryotic cells?
Structure fundamentally the same but it’s packaged differently. Generally only have one molecule of DNA, a chromosome which is supercoiled to make it more compact. Genes often grouped into Operon
How does a prokaryotic ribosome compare to a eukaryotic ribosome?
Prokaryotic ribosomes are smaller than those is eukaryotic cells. Relative size is determined by the rate at which they settle, or form a sediment in solution.
Same function but produce less complex proteins in prokaryotes.
What is a bacterial cell wall made of?
Peptidoglycan
How does a prokaryotic flagella compare to a eukaryotic flagella?
Prokaryotic flagella is thinner than eukaryotic and does not have the 9 + 2 arrangement. The energy to rotate the flagella is bacteria comes from chemiosmosis, not from ATP.
How does a flagellum attach itself to prokaryotes?
Attached to cell membrane of a bacterium by basal body and is rotated by a molecular motor
What is the theory of endosymbiosis?
The theory of endosymbiosis is that mitochondria and chloroplasts were formerly free living bacteria ( prokaryotes).
Theory is that these were taken inside another cell as an endosymbiont that lives inside the body or cells of another organism.
