Eukaryotic Cell S&F Flashcards
size of viruses, prokaryotic and eukaryotic cells (diameter)
v: 20-100 nm
prok: 0.2-10 μm
euk: 10-100 μm
Key diff.s between prok. and euk. cells (5)
1) Membrane-bound organelles not present in prok. (no endomembrane system)
2) No nucleoli vs nucleoli present
3) Single circular chromosome vs multiple linear chromosomes
4) mode of cell division: binary fission vs mitosis
5) No meiosis in prok.
Algae, yeast, amoeba, phytoplankton. What are they?
Unicellular eukaryotic organisms
Cell size is kept (___) to maximise (______), thus allowing (__________)
small; SA:V; ↑ chemical exchanges with the extracellular environment and diffusion of materials to occur at a faster rate
Lower limit of cell size is determined by
Min. amount of space needed to contain the essential elements of its function
Upper limit of cell size is determined by
SA: V needed for exchange of materials between cell and its environment
The cytoplasm refers to (______), except (____).
All organelles + cytosol; except nucleus
Prok. vs euk. ribosome (size and name)
Euk.: 30nm, 80S
Prok.: slightly smaller, 70S
Proteins synthesised by ribosomes on rER are destined for _____ (3)
1) Export out of cell
2) Insertion into membrane (e.g. rER)
3) Transport to membrane-bound organelles (e.g. hydrolytic enzymes in lysosomes)
Function of microtubules (3)
1) Structural support
2) Involved in transporting molecules from one site to another
3) Component of spindle fibres
Function of MTOCs
Give anchorage and orientation to the microtubule assembly
Function of microfilaments (2)
1) involved in cell motility
2) Changes in cell shape
Function of intermediate filaments (2)
1) Stabilise organelles like nucleus
2) involved in specialised cell junctions
Structure and subunits of microtubules, microfilaments and intermediate filaments
tubulin (helical arrangement), actin (twisted double strand of beads), various proteins (rope-like bundles)
Homogenisation [definition]
Disruption of cells and release of the individual cellular components
Methods for homogenisation (7)
1) Ultrasound
2) Pressure cell
3) Mortar, Pestle, and abrasive material like sand/silica
4) Osmotic lysis
5) Blender
6) Use of chemicals like detergents to dissolve plasma membrane
7) Electroporation
Conditions needed for homogenisation (4)
1) Isotonic medium
2) Buffer solution to maintain suitable pH
3) Temp. of 4℃
4) Temp. > 0℃
Purpose of conditions for homogenisation (4)
1) Prevent osmotic damage in organelles
2) constant pH to prevent change in protein structure → membrane stability
3) keep enzymes inactive (to stop cellular processes)
4) above 0℃ to prevent autolysis
Differential centrifugation [definition]
Purification of cell components
Purpose of centrifugation
To separate organelles
Methodology of centrifugation (3)
1) the homogenate is subjected to progressively increasing speeds and duration of centrif. to separate particles in descending size and density.
2) After each speed, the supernatant can be drawn off and re-centrifuged at a higher speed and for a longer duration.
3) A series of pellets containing cell organelles of decreasing size can thus be obtained.
Centrifugation is possible because
Most organelles are discrete particles with unique sizes and densities
Autoradiography [definition]
Use of X-ray film to visualise molecules or fragments of molecules that have been radioactively labelled
Purpose of autoradiography (2)
1) To identify sites of synthesis and cellular distribution of metabolic products
2) used with LM/EM to trace secretion products from their synthesis sites to their eventual destinations
Methodology of autoradiography (3)
1) cells/tissue sections as are incubated w radioactive substances
2) Cell/tissue is mounted on glass slides, which is dipped into photographic emulsion
3) The decay of radioactive isotopes create dark spots on the emulsion, allowing for identification of where the radioactive substance is
Purpose of homogenisation: to break (_______________) and to release (_____).
Tissues into smaller pieces; organelles
Advantages of membranous organelles (2)
1) maintenance of characteristic diff.s between contents of each organelle and cytosol
2) increase efficiency of reactions by increasing membrane surface area
Cell theory [definition]
1) All living organisms are composed of one or more cells
2) Cells are the basic units of structure, organisation and function
3) All new cells arise from old/pre-existing cells
