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3 main types of filaments in the cell? which is the most stable
- Intermediate filaments
although there are tonnes of proteins making up intermediate filaments, name 4 particularly important groups
the accumulation of keratins (cytokeratins) is reffered to as? it most often happens where?
- outside ofr epithelial cells
Which intermediate filament protein class is the most common? Name two proteins in this class
- Glial fibrilar acidic protein (GFAP)
What is the intermediate protein group that is found in major connections in neurons
Where do we find lamins?
Within the cell nuc;leus, forming the nucleuar lamina (just inside the nuclear envelope)
Are inclusions enclosed by a membrane? What distinguishes them from an organelle?
Give 4 good examples of common inclusions in cells
- Fat droplets
- Glycogen granules - Aggregate of carb polymer
- Lipofuscin - the wear and tear pigment yellowish brown
- Hemosiderin - often derived from phagocytosis of red blood cells, dense brown aggregate of denatured ferritin proteins with iron atoms bound
Ribosomes are formed of?
rRNA and many proteins
The surface of the rough ER is basophilic/acidophilic and has what on its surface?
- Basophilic because of protein production and all the phosphates in the area
What does the Golgi do?
Furhter processes proteins made in the RER
What are the 2 faces of the golgi
- Cis where they enter
- trans where they leave
What is autophagy
When lysosomes fuse with old useless organelles to destroy them
Differentiate between a primary lysosome and a secondary lysosome. What about a residual body?
- Primary is essentially a fresh non fused lysosome with unused chemicals
- Secondary has already fused with a vesicle and started working
- Residual body is whats left and undigested after a lysosome is done all of its work on the vessicle
describe the 2 mitochondrial membranes
- outer = porous and encloses intermediate space
- inner = very folded encloses gel like matrix
Electron transport chain occurs on which membrane of mitochondria
when do mitochondria release cytochrome c and what does it do
What do proteasomes do?
Degrade improperly folded proteins after being tagged with ubiquitin
WHat are in peroxisomes
Enzymes for oxidation and detoxification, also catalase to break diown H2O2
Describe what microtubules look like
semirigid tubular structures
Whats bigger microtubules or actin
MIcrotubules are biggest then intermediate then actin is the smallest (often reffered to as microfilaments
What are 2 good uses for microtubules
Maintaining cell shape and trcks for transport of vesicles by motor protein kinases
Which cytoskeletal filament is most responsible for movement
What are the motor proteins that work on actin
Which of the cytoskeletal filaments is the most stable and almost purely for structure
What is typically the largest structure within a cell
3 main structures of the nucleus
- Nuclear envelope
Describe the nuclear envelope
- 2 membranes, inbetween is perinuclear space
- outer membrane is contuous with the RER
- inner membrane is continuous with the nuclear lamina which stabilizes the envelope
What connects the two nuclear membranes and allows transfer between the inside and outside of the nucleus , what is the main component making it up
- nuclear pore complexes
can ions move through nuclear pore complexes?
Yes but larger molecules are regulated both ways
What is chromatin
Combination of DNA and its associated proteins
What is chromatin active in transcription called? what about inactive? What colour do they stain?
- Euchromatin - light
- heterochromatin - dark
to pack DNA in the chromatin it is wrapped around what structure? This forms a what? Are chromatin condensed in any other ways?
- Yes but less understood, involves other proteins including complexes of condensins
What is the part of chromatin where rRNA transcription and ribosomal sub unit assembly occur called? basophilic/acidophilic?
- basophilic, it is very electron dense
What is the cell cycle?
Sequence of events that controls cell growth and division
What is the longest phase of the cell cycle
G1 includes all preparation for DNA replication and occurs right after mitosis
What comes after G1 phase?
S phase or phase of DNA and histone synthesis
G2 phase what occurs?
- Cell prepares for division through mitosis
- ex) accumulate proteins needed for division
What cytoplasmic proteins control the cell cycle? What do they bind too?
- cyclin dependants kinases
WHat do CDKs (cyclin dependant kinases) do?
phosphorylate and activate enzymes and transcription factors whos functions characterize each cycle
When do the cyclins of each phase change?
- Only once all activites of a phase are complete and the cell is ready to move onto the next phase
- at this point proteasomes eat up the previous cyclin and the new one takes over
What is the G1 restriction point
one of many slow down restriction points where problems that may have occurred with DNA during growth or replication is fixed so that problems do not occur further
What are the 4 phases of mitosis and what occurs during them
- Prophase - chrom condense, envelope dissolves, microtubular spindles form
- metaphase - chromosomes align
- anaphase - when chromes separate towards two centrosomes
- telophase - nuclear envelope reforms around separated chromsomes
Telophase ends with what? What filaments are responsible for this? What organ uses this same system for contraction?
- cytokinesis or cell cleavage
- contractile ring of actin and myosin
So when does cytokinesis occur?
It is essentially the last section of telophase
What are kinetochores?
Large protein complexes on the mitotic spindle that the chromosomes attach too
What is the name for the combination of G1 S and G2 phase
What signals from the environment activate cell cycling?
mitogens or growth factors
What is the function of the Golgi?
Further process proteins made in the rough ER as well as package for secretion and other roles
The Golgi is made of stacked membranous?
The Golgi has 2 faces describe each. it also has an area for enzymatic modification what are these called?
- cis = vesicle receiving
- trans = vesicle releasing
- medical cisternae
What are the names of the proteins that guide vesicles through the golgi
coat proteins COP1 and COP2
What are 2 important protein modifications that occur in the Golgi?
Modified proteins leave the Golgi in what? how do they direct their movement? Where are 3 places they could go?
- coat proteins
- lysosomes, plasma membrane, exocytosis
Define a primary lysosome vs a secondary lysosome?
- primary leaves the Golgi containing inactive acid hydralases
- secondary are much more variable having fused with vesicles from endocytosis and having digested the contents
Lysosomes digesting uneeded or non-functional organelles by fusing with their membranes
Where do the products of secondary lysososme digestion go? If the material stays in a vesicle what is it then called?
- Into the cytoplasm to be re used
- residual bodies
What is a proteasome?
Small cytoplasmic protein complex that degrades improperly folded proteins after being tagged with ubiquitin
Main function of mitochondria?
How do mitochondria reproduce?
- Fission of older mitochondria
- like bacteria
2 membranes of mitochondria? Whats inbetween them?
- porous outer membrane
- inner membrane (with all the folds)
- intermembrane space
Enzymes found in the mitochondrial matrix are used for what processes?
- beta oxidation
- citric acid cycle
Where in the mitochondria does the electron transport chain happen?
On the inner membrane
Stressed cells can release what from the mitochondria to cause apoptosis? what part of the mitochondria does it come from?
- Cytochrome C
- inner membrane
What is a peroxisome? What is found in it? What is its function
- small spherical organelle containing enzyme
- enzymes for metabolic reactions, oxidation and detoxification as well as catalase to break down H2O2 resulting from the earlier stated reactions
3 types of polymers found in the cytoskeleton?
- microfilaments (actin)
- intermediate filaments
Describe the structure of microtubules
semirigid tubular structure made of polymerized tubulin heterodimers
What makes up microtubules
polymerized tubulin heterodimers
What are 2 functions of microtubules
- maintaining cell shape
- tracks for transport
What are the 2 proteins used to transport vesicles and organelles along the microtubules?
- motor protein kinesin
What are the motor proteins that move along with actin?
3 things actin contraction and movement is important for in the cell?
- cell cleavage
intermediate filaments are composed of various protein subunits which vary within different cells, what are 4 of them?
- neurofilament proteins
What are inclusions?
Non metabolically active storage sites
Differentiate in movement between COP 1 and COP 2
COP 1 moves retrograde and COP 2 moves forward
What is a zymogen granule?
secretory granule with dense contents of digestive enzymes
What is a heterolysosome?
Lysosome after ingesting something to digest
What is ubuiquitin
protein that helps lead misfolded proteins to their death
The mitochondria innermembrane has infoldings called?
What is a large organized congregation of microtubules called?
What are the subunits of the microtubule
alpha and beta tubulin
What creates microtubules?
Microtubule organizing centers
What is meant when said that microtubules show dynamic instability? The rate of this based on the concentration of what 4 things?
They are contantly polymerizing an depolymerizing at a constant rate
- and Microtubule associated proteins (MAPs)
What is the dominant MIcrotubule organizing center in most cells? What is it made up of?
- 2 centrioles at right angles to eachother
What is meant by actin treadmilling
The fact that one end of actin is always being added to and the negative end is always being dissociated and therefore actin is very dynamic in its movement and a monomer moves from end to the other like being on a treadmill
What is a stress fiber?
Cells attached to firm substrates actin filaments can get concentrated into parralell bundles called stress fibers
What is a barr body?
What is a karyotype
the collection image of an individuals chromosomnes
What is a cyclin?
cytoplasmic proteins that regulate cell cycling
What are mitogens?
Postmitotic protein signals that activate cell cycling
What is interphase?
Combination of G1, G2 S phase
What serves as a site for attachment of microtubules on the chromosome?
A large protein complex called the kinetochore
What is synapsis?
Where homologous chromsomes of each pair come together
Crossover is when?
Their is reciprocal DNA exchange between aligned maternal and paternal chromsomes
What is a pyknotic nuclei?
dense darkly stained blobs in a dying apopotic cell