cell fractionation, nucleus, endomembrane system, cytoplasm/mitochondria, plastids Flashcards
what is cell fractionation’s purpose and how does it work basically?
cell fractionation separates organelles based on a density gradient
we break cells open, destroy plasma membrane and release subcellular structures but keep those intact)
You get a really thick substance, and spin it.
Density gradient centrifugation results in lots of force at the bottom of test tube and very little at the top (results in molecular separation/density gradient, which separates different subcellular structures!)
what defines a eukaryotic cell?
it has a nucleus and a nuclear envelope!
what is the nuclear envelope?
a double layered structure (4 phospholipids thicc) surrounding the nucleus, like the “membrane of the nucleus”
what are nuclear pores/nuclear pore complexes? function?
holes/gates restricting very large molecules from passing through (ex chromosomes, glucose), letting through smaller molecules (ex cations, anions, mRNA)
what is in the nucleus?
all chromosomal DNA! usually seen as chromatin
what is chromatin?
chromatin= DNA + protein
relaxed form of chromosomes, chromatin called chromosomes when it condenses
what is the nucleolus? what happens in the nucleolus?
T/F: cells only have one nucleolus
an area of increased transcriptional activity and protein assembly. Where genes for rRNA are being produced!
false: cells can have several nucleoli regions!
what is a nucleosome?
DNA wrapped up on histone proteins
what 2 components hold chromatin in place?
nuclear matrix and nuclear lamina
what is the nuclear matrix? nuclear lamina? functions?
nuclear matrix= network of structural proteins that helps organize the chromatin (‘relaxed’ DNA). Maintains structural integrity of nucleus
Keeps any chromosomal DNA from leaving (chromosomes “tied” into place)
nuclear lamina= attaches to both chromatin and nuclear envelope. maintains nuclear shape
5 components of the endomembrane system? components are all ___ with one another
plasma membrane
nuclear envelope
endoplasmic reticulum (RER and SER)
Golgi apparatus
Lysosomes
components all continuous with one another, a flow
what tiny structure shuttles substances between components of the endomembrane system?
vesicles
RER is continuous with __. what is its primary characteristic (hint: name)
SER. dotted with ribosomes, hence rough
what are ribosomes? function?
bigass Large enzymatic complexes responsible for protein assembly!
read mRNA and convert that into protein language (site of mRNA translation)
what 3 places can you find ribosomes?
- cytoplasm
- surface of RER,
- inside the mitochondria or chloroplasts!
what happens if a protein on the ribosome has a localization sequence?
a signal recognition protein will interact with the protein, tethering the ribosome to the surface of the RER.
consequently, the protein produced by that ribosome will be translocated into the lumen (inside) of RER and modified (usually into conjugated molecules, or sent to SER)
why do proteins become conjugated molecules?
Proteins often expressed on surface of cell (surface of cells covered in carbohydrates).
This allows proteins to stay embedded in cell membrane, anchoring it
what processes happen in the SER?
Produces lipids/steroids (ex. cholesterol)
hydrolysis of glycogen
breakdown of xenobiotics
in muscle cells: Ca storage/release
what are xenobiotics?
substances foreign to the cell
what is the sarcoplasmic reticulum? where is it found in abundance?
basically, the SER but in muscle cells.
releases/stores Ca
release of Ca in the sarcoplasmic reticulum in muscle cells triggers ___?
muscle contractions!
what are cisternae? what component of endomembrane system are they associated with?
flattened sacs found in golgi apparatus!
what 2 components are associated with the golgi?
cisternae and vesicles
T/F: the endomembrane system is absent in prokaryotes
true
how do vesicles come in/out of the golgi?
enter through the cis side, exit through the trans side
what happens to proteins in the golgi?
proteins get sorted even more based on destination and get final modifications
why is golgi important particularly in plants?
it’s the site of rigid cell wall/cell plate polysaccharide formation!
how do vesicles move throughout the cell?
along cytoskeleton “highways”
what happens to vesicles once they leave the golgi?
Vesicles can a) fuse w plasma membrane and material can be released
b) can associate with inside/outside of membrane
lysosomes contain lots of ____. these are responsible for __?
Lysosomes have lots of hydrolytic enzymes (responsible for “intracellular digestion”)
lysosomes primary function?
Break down molecules into smaller ones, hydrolyze molecules. ex. polysaccharides
what are primary lysosomes?
originate from Golgi, contain digestive enzymes. They are in the cytosol, ready to go.
what are secondary lysosomes and how do they form? are also called ___
Foreign substances enter the cell through phagocytosis, forming a phagosome: the phagosome FUSES with a primary lysosome to form a secondary lysosome or phagolysosome
genetic disorder linked to lysosome dysfunction?
tay sachs (lethal). an accumulation of a complex polysaccharide that lysosomes cannot break down
lysosomes are important for _____
intracellular maintenance
what structure is responsible for dealing with denatured proteins? (hint: similar to chaperone proteins)
proteasomes!
how do proteasomes work/function?
recycle/break down proteins! Hydrolyzes denatured protein back into its amino acids that can be used for generation of new proteins
peroxisomes and what is their function?
supplementary components of smooth ER.
Collect and break down toxic byproducts of metabolism using specialized enzymes. When smooth ER becomes “overwhelmed”, peroxisomes “help out” (ex. in the Breakdown of xenobiotics)
what are glyoxysomes? found only in __?
Glyoxysome= variation of peroxisome. Convert lipids to carbohydrates for plant growth/germination (aka gluconeogenesis)!
found only in plants!
T/F: peroxisomes and glyoxysomes are derived from the golgi
false! they are derived from the ER!
genetic disorder associated w peroxisome dysfunction?
ALD= in adolescence, one’s personality may completely switch due to reasons that aren’t psychiatric
what is the plasma membrane/function?
Plasma membrane= Semi permeable barrier separating inside of cell from extracellular environment.
T/F: complex molecules can diffuse across the plasma membrane
false: complex molecules need to be TRAFFICKED across the plasma membrane, unlike
what is the cytoplasm? cytosol?
cytoplasm= everything inside the plasma membrane
cytosol= fluid inside the cell. the site of many cellular processes
what is one cool function of mitochondria aside from being the powerhouse of the cell?
An intrinsic pathway of apoptosis (cell suicide)
the mitochondria is a ___ membrane structure
dual (2 layers)
what is the mitochondrial matrix?
fluid component of mitochondria, interior of mitochondria.
what are cristae? why is this good?
the result of the inner membrane of the mitochondria folding inward, allows for large surface area
T/F: mitochondria does not have ribosomes or DNA.
T/F: mitochondrial DNA is circular
false! Have their own ribosomes (so they can perform DNA transcription/translation a bit!)
Retains some of their own (circular) genetic material!
true: DNA in mitochondria is circular
how do mitochondria replicate?
Replicate by binary fission based on cellular need!
what are plastids? example of a plastid?
Plastids= class of organelles occurring only in plants and some protists
ex. chloroplasts
do chloroplasts have a genome? shape?
yes, and it’s circular
what are chromoplasts and their function?
Light harvesting pigment complexes
make up bright colors of flower plants, attract pollinating insects.
what are leucoplasts and function?
cousins of chloroplasts lol
responsible for storage and breakdown of starch.
central vacuoles functions? where are they found?
Important for storage of materials (ex. dyes):
a) Store “toxic” compounds like caffeine that deter animals from plants so it won’t be eaten
b) Store water and maintain structure of cell: can expel excess water
found primarily in photosynthetic organisms but not absent in animal cells
what organelle can replicate independently from its host cell?
mitochondria
