Chapter 2 Flashcards
What is the ultrastructure of a cell?
The detailed structure of a cell that can only be seen using an electron microscope.
Define resolution
The shortest distance between two objects that are still seen as separate objects.
Define magnification
How many times the image size is bigger than the actual size.
Why do electron microscopes have a higher resolution that light microscopes?
Electrons have a shorter wavelength than light waves.
What is a cell?
The basic unit of a living organism.
What is a cell organelle?
Smaller, cellular structures inside a cell which carry out different functions.
Why is the cytoplasm not a cell organelle?
It is mostly made up of water (70%)
Describe the nucleus.
Double membrane bound organelle which has perforations known as the nuclear pore.
What are the functions of a nucleus?
Controls all cell activities.
Stores genetic informations.
Codes for proteins.
Describe the mitochondria
A double membrane bound structure where the inner membrane folds to give the cristae.
What is the function of the mitochondria?
It is the site of respiration.
Describe the ribosome
A structure with no membrane and is composed of two subunits (smaller and larger) where the smaller has a binding site.
Describe the Golgi body
A fluid filled, flattened and curved structure.
Describe the centriole
A structure that is: Hollow Not membrane bound Made of nine sets of microtubule triplets Cylinder shape
What is the function of a centriole?
It makes the spindle fibres which plays a role in the separation of chromosomes during mitosis.
Describe the chloroplast
A double membrane bound structure where the inner membrane forms the thylakoid.
What is the function of the chloroplast?
It is the site of photosynthesis. The thylakoid is where the light dependant reactions take place and the stroma is where the light independent reactions take place.
What separates the chromosomes in plant cells during mitosis?
Microtubules
Describe the vacuole
One membrane bound structure, known as the tonoplast. Inside is a fluid (cell sap) which contains ions, glucose and water.
What is the function of the tonoplast?
Supports the cell by keeping it turgid.
Which structures are only found in animal cells?
Centrioles
Microvilli
Which structures are only found in plant cells?
Chloroplast Vacuole Middle Lamella Cellulose cell wall Plasmodesmata
What are the similarities and differences between prokaryotic and eukaryotic cells?
(Feature-Prokaryotic,Eukaryotic)
Nucleus- none, present
DNA- circular, linear
DNA organisation- fold and condense DNA, associated with proteins (histones)
Extra chromosomal DNA- Plasmids, Only present in mitochondria and chloroplast
Organelles- not membrane bound, membrane bound
Cell wall- peptidoglycan, none in animals, chitin in fungi and cellulose in plants.
Ribosomes- 70S (16nm), 80S (22nm)
Cytoskeleton- present, present but more complex.
Reproduction- binary fission, asexual or sexual.
Cell type- Unicellular, unicellular or multicellular
Cell surface membrane- present, present
What are the similarities between prokaryotic and eukaryotic cells?
Cell surface membrane, ribosomes (but of different sizes), DNA and RNA
Where is the RNA in prokaryotic cells?
ribosomes
Which structures are present in prokaryotic cells?
Nucleoid, mesosome, cytoplasm, cell wall, cytoplasm, cell wall, ribosome, plasmid, flagellum (in some), cell surface membrane, slime capsule (in some), food storage (shown as shaded dots), bacterial chromosome
What is the nucleoid?
Part of the cytoplasm where the main loop of DNA is present
What is the mesosome and what is its function?
made by the folding of the cell surface membrane. Its function is to keep enzymes for respiration.
What is the plasmid?
Extra, smaller, loop of DNA
what is the cell wall in prokaryotes made of?
Peptidoglycan/murein
Which structures are only present in bacterial cells?
Mesosome and plasmid
Why is binary fission not known as mitosis?
Prokaryotic cells do not have linear DNA, nucleus or DNA bound to proteins, unlike in eukaryotic cells.
What is the Endosymbion theory?
The mitochondria and chloroplast are formed from a PK cell. When the EK cell was made, the PK cell moved inside the EK cell. With time, two organelles inside a EK cell was made.
What is the evidence for Endosymbion theory?
Prokaryotic cells, mitochondria and chloroplast:
have 70S ribosome
have loop of DNA
Are of similar sizes
What are different ways of preparing samples?
Dry mount, Wet mount, Squash slides, Smear slides
How do you prepare a dry mount?
Solid specimens should be sectioned. A thin slice should then be placed onto the centre of a microscope slide and a cover slip placed on top.
How do you prepare a wet mount?
Specimens are suspended in a liquid i.e. water or immersion oil. A cover slip is placed from an angle.
How are squash slides prepared?
A wet mount is prepared first. A lens tissue is then used to gently press the cover slip down.
How are smear slides prepared?
The edge of a slide is used to smear the sample, creating a thin and even coating on another slide. A cover slip is then placed over the sample.
Which stains are used for negative stain technique?
Nigrosjn or Congo red
What are the stages involved in the production of preprepared slides?
Fixing, Sectioning, Staining, Mounting
What is the resolution for a light microscope?
50-200nm (200nm)
What is the magnification of a light microscope?
x1000-x1500
What is the resolution for an electron microscope?
0.05-1nm (0.1nm)
What is the magnification of am electron microscope?
x100000-x500000
Define empty magnification
When magnification is increased without increase in resolution so no more detail is visible
