UNIT 2 - A 2.2 - Cell Structure Flashcards
What is cytology?
the branch of biology that studies all aspects of the cell
how many micrometers are in a millimeter?
1000
How many nanometers are in a millimeter?
1 000 000
How many nanometers are in a micrometer?
1000
what do microscopes need in order to observe cells and especially their subunits?
high magnification and resolution
What is magnification ?
the increase in an object’s image size compared to its actual size
What is resolution?
the minimal distance between two points/objects at which they can still be distinguished as two
What happens when the resolution of a microscope increases?
the microscope will reveal greater detail
How do light microscopes form an image?
they use light which passes through the specimens
What are stains used for in a light microscope?
to improve the visibility of structures
What do electron microscopes (EMs) use to create an image?
electrons passing through a specimen
What is the order (from largest to smallest) of cells/subunits?
cells, bacteria, viruses, membranes, molecules
What is the field of view/vision?
total area visible when looking through a microscope’s ocular/eyepiece
What are the two general types of micrometers?
ocular and stage
where is the graticule (ocular micrometer) located?
in the eyepiece
How are the units on the graticule calibrated?
using a stage micrometer
How can the size of the image being examined under a microscope be determined?
By comparing the units of the graticule to the know unit size of the stage micrometer
What is the formula to calculate magnification?
measured size of image/actual size of specimen
What benefits do electron microscopes have over light microscopes?
Because electrons have much shorter wave lengths, the EM has a 1000x greater resolving power than a light microscope and the ability to magnify objects over 500000x
What are the two general types of EMs?
scanning electron microscope (SEM) and transmission electron microscope (TEM)
How do SEMs work?
They use a beam of electrons to scan the surface of a specimen
How do TEMs work?
They aim a beam of electrons through a very thin section of specimen which allows its inner structure to be viewed
What are two techniques used when working with an EM?
freeze fracture and cryogenic electron microscopy
What is freeze fracture?
The process of preparing a sample for observation with an EM, involves rapid freezing of specimen, then breaking the specimen apart
What is enabled with the use of cryogenic electron microscopy?
an image to be formed using computers showing the 3D framework of proteins involved with the function of a cell
What are some examples of how our knowledge has been enhanced using cryogenic electron microscopy?
virus composition and structure, cell membrane components and their arrangement, cellular protein synthesis, hereditary expression and regulation
What are the cons of electron microscopes?
They are expensive, require extensive training to operate, and require non-living specimens
What are two preparation techniques developed recently for the study of cells using light microscopy?
fluorescent stains and immunofluorescence
What are fluorescent stains?
substances/dyes that combine with specific cellular components
Why are fluorescent stains used?
They are accepted by certain parts of the specimen after being exposed to UV light and those parts start to fluoresce and assorted colours are produced, allowing for more detailed visibility
What does immunofluorescence allow?
greater visibility of living tissue
How does immunofluorescence work?
because it involves antibodies already combined with dyes, specific antibodies combined with unique coloured dyes recognize and combine with target molecules
What is the technique of immunofluorescence often used for?
Detecting viral proteins that have infected cells
What is the condenser on a light microscope?
Located between the stage and the light source, it has a lens that directs light rays from the light source through the specimen
What is a brightfield microscope?
it uses visible light so the specimen is viewed against a light background
What is a darkfield microscope?
An opaque lens is used in the condenser which blocks direct light, specimen is viewed against a dark background
What is a phase-contrast microscope?
A special condenser is used to show detailed images of a specimen without staining
What structures do all cells contain?
DNA as genetic material, cytoplasm composed of mainly water, plasma membrane composed of lipids surrounding the cytoplasm
What is a cell’s means of storing and transferring information?
DNA
What allows the production of the exact proteins needed for passing distinctive characteristics from cell-cell and organism-organism?
The four different nucleotides making up DNA and their sequences as well as their ability to form big chains
What sort of role do enzymes serve in chemical reactions?
Controlling
What controls the production of enzymes?
DNA
Where is cytoplasm found?
WIthin the boudary of a cell
What is cytosol?
Matrix composed mainly of water which is located in cytoplasm
What does cytosol contain?
Everything necessary for a cell to conduct its day-to-day activities: includes different carbon compounds, ions and other inorganic molecules
Where do most chemical reactions within a cell take place?
Within the cytoplasm
What is the major component of the plasma membrane surrounding a cell?
two layers of lipids combined as a bilayer
What does the membrane of a cell control the interactions between?
a cell’s contents and the exterior
What do membrane proteins provide?
identity properties to the cell
What is the diameter of most prokaryotic cells?
less than 1 micrometre
What are two examples of prokaryotic organisms?
bacteria and archaea
What are different factors differentiating prokaryotes?
nutritional requirements, sources of energy, chemical composition and morphology (shape)
What are the features of a prokaryotic cell?
cell wall, plasma membrane, flagella, pili, ribosomes, nucleoid
What does the cell wall of a prokaryotic cell do?
protects and maintains shape, keeps bacterial cell from rupturing when water pressure is greater inside than outside
What is the cell wall of a prokaryote made from?
peptidoglycan
What is peptidoglycan?
a carbohydrate-protein complex
What is the capsule on some prokaryotes?
and additional layer of a type of polysaccharide
What does the capsule do?
makes it possible for some bacteria to adhere to structures such as teeth, skin, and food
What is one major way to classify bacteria?
by their ability to retain a dye called crystal violet
What happens to the cell wall of a “Gram-positive” bacteria when it is exposed to crystal violet?
it takes a violet/blue appearance
What’s the difference between “Gram-positive” and “Gram-negative” bacteria?
“Gram-negative” bacteria don’t retain crystal violet and don’t appear blue/violet when exposed to the dye
What are two examples of Gram-positive bacteria?
Bacillus and Staphylococcus
What are pili?
The hair-like growths on the outside of some bacteria cell walls
What are the functions of pili?
attatchment and sexual reproduction
What is the pili’s function in sexual reproduction?
joining bacterial cells in preparation for the transfer of DNA from one cell to another
What does a prokaryote’s flagella/flagellum do?
Allow a cell to move
Where is the flagellum anchored?
to the cell wall and plasma membrane
Why are there no specialized areas within the cytoplasm of a prokaryote?
Because there are no internal membranes
Where do all cellular processes within a prokaryotic cell occur?
Within the cytoplasm
What are the two subunits of making up ribosomes?
a protein and ribosomal RNA
What does the nucleoid region of a bacterial cell contain?
a single, long, continuous, circular thread of DNA (the bacterial chromosome)
Why are bacterial chromosomes described as naked loops?
Because the DNA of a prokaryotic cell is not associated with histones
What is the nucleoid region of a prokaryotic cell involved with?
cell control and reproduction
What are plasmids?
small, circular, DNA molecules contained in prokaryotes
Though it is not required under normal conditions, what can plasmids help a prokaryotic cell to do?
adapt to unusual circumstances
How do prokaryotic cells divide?
binary fission
What occurs during the process of binary fission?
the DNA is copied, resulting in two daughter chromosomes which become attached to different regions on the plasma membrane and the cell divides into two genetically identical daughter cells
What does binary fission include the use of specialized fibres for?
lengthening of the cell and the newly produced DNA dividing into parts
What do eukaryotic cells occur in?
organisms such as algae, protozoa, fungi, plants, and animals
What are organelles?
non-cellular structures that carry out specific functions
What do organelles allow for in eukaryotic cells which is not a characteristic of prokaryotic cells?
compartmentalization
What does compartmentalization do?
Enables different chemical reactions to be separated and allows chemicals for specific reactions to be isolated which results in increased efficiency
When is compartmentalization especially important?
When adjacent chemical reactions are incompatible
Where does cytoplasm occur?
inside the plasma membrane and outside the nucleus of all eukaryotic cells
What is the fluid portion of the cytoplasm around the organelles called?
Cytosol
What is a cytoskeleton?
small fibres and rods within eukaryotic cytoplasm
What does the cytoskeleton create?
A complex internal structure
What is the difference between eukaryotic and prokaryotic cytoplasm?
Prokaryotic cytoplasm does not have a cytoskeleton
What is the cytoskeleton made of?
protein
What are the functions of the cytoskeleton?
maintaining cell shape, anchoring some organelles, helping cellular movements, providing a means for some organelles to move within the cell