cell fractionation, nucleus, endomembrane system, cytoplasm/mitochondria, plastids

Question 1

what is cell fractionation’s purpose and how does it work basically?

Answer 1

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!)

Question 2

what defines a eukaryotic cell?

Answer 2

it has a nucleus and a nuclear envelope!

Question 3

what is the nuclear envelope?

Answer 3

a double layered structure (4 phospholipids thicc) surrounding the nucleus, like the “membrane of the nucleus”

Question 4

what are nuclear pores/nuclear pore complexes? function?

Answer 4

holes/gates restricting very large molecules from passing through (ex chromosomes, glucose), letting through smaller molecules (ex cations, anions, mRNA)

Question 5

what is in the nucleus?

Answer 5

all chromosomal DNA! usually seen as chromatin

Question 6

what is chromatin?

Answer 6

chromatin= DNA + protein
relaxed form of chromosomes, chromatin called chromosomes when it condenses

Question 7

what is the nucleolus? what happens in the nucleolus?
T/F: cells only have one nucleolus

Answer 7

an area of increased transcriptional activity and protein assembly. Where genes for rRNA are being produced!

false: cells can have several nucleoli regions!

Question 8

what is a nucleosome?

Answer 8

DNA wrapped up on histone proteins

Question 9

what 2 components hold chromatin in place?

Answer 9

nuclear matrix and nuclear lamina

Question 10

what is the nuclear matrix? nuclear lamina? functions?

Answer 10

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

Question 11

5 components of the endomembrane system? components are all ___ with one another

Answer 11

plasma membrane
nuclear envelope
endoplasmic reticulum (RER and SER)
Golgi apparatus
Lysosomes

components all continuous with one another, a flow

Question 12

what tiny structure shuttles substances between components of the endomembrane system?

Answer 12

vesicles

Question 13

RER is continuous with __. what is its primary characteristic (hint: name)

Answer 13

SER. dotted with ribosomes, hence rough

Question 14

what are ribosomes? function?

Answer 14

bigass Large enzymatic complexes responsible for protein assembly!
read mRNA and convert that into protein language (site of mRNA translation)

Question 15

what 3 places can you find ribosomes?

Answer 15

• cytoplasm
• surface of RER,
• inside the mitochondria or chloroplasts!

Question 16

what happens if a protein on the ribosome has a localization sequence?

Answer 16

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)

Question 17

why do proteins become conjugated molecules?

Answer 17

Proteins often expressed on surface of cell (surface of cells covered in carbohydrates).
This allows proteins to stay embedded in cell membrane, anchoring it

Question 18

what processes happen in the SER?

Answer 18

Produces lipids/steroids (ex. cholesterol)
hydrolysis of glycogen
breakdown of xenobiotics
in muscle cells: Ca storage/release

Question 19

what are xenobiotics?

Answer 19

substances foreign to the cell

Question 20

what is the sarcoplasmic reticulum? where is it found in abundance?

Answer 20

basically, the SER but in muscle cells.
releases/stores Ca

Question 21

release of Ca in the sarcoplasmic reticulum in muscle cells triggers ___?

Answer 21

muscle contractions!

Question 22

what are cisternae? what component of endomembrane system are they associated with?

Answer 22

flattened sacs found in golgi apparatus!

Question 23

what 2 components are associated with the golgi?

Answer 23

cisternae and vesicles

Question 24

T/F: the endomembrane system is absent in prokaryotes

Answer 24

true

Question 25

how do vesicles come in/out of the golgi?

Answer 25

enter through the cis side, exit through the trans side

Question 26

what happens to proteins in the golgi?

Answer 26

proteins get sorted even more based on destination and get final modifications

Question 27

why is golgi important particularly in plants?

Answer 27

it’s the site of rigid cell wall/cell plate polysaccharide formation!

Question 28

how do vesicles move throughout the cell?

Answer 28

along cytoskeleton "highways"

Question 29

what happens to vesicles once they leave the golgi?

Answer 29

Vesicles can a) fuse w plasma membrane and material can be released b) can associate with inside/outside of membrane

Question 30

lysosomes contain lots of ____. these are responsible for __?

Answer 30

Lysosomes have lots of hydrolytic enzymes (responsible for “intracellular digestion”)

Question 31

lysosomes primary function?

Answer 31

Break down molecules into smaller ones, hydrolyze molecules. ex. polysaccharides

Question 32

what are primary lysosomes?

Answer 32

originate from Golgi, contain digestive enzymes. They are in the cytosol, ready to go.

Question 33

what are secondary lysosomes and how do they form? are also called ___

Answer 33

Foreign substances enter the cell through phagocytosis, forming a phagosome: the phagosome FUSES with a primary lysosome to form a secondary lysosome or phagolysosome

Question 34

genetic disorder linked to lysosome dysfunction?

Answer 34

tay sachs (lethal). an accumulation of a complex polysaccharide that lysosomes cannot break down

Question 35

lysosomes are important for _____

Answer 35

intracellular maintenance

Question 36

what structure is responsible for dealing with denatured proteins? (hint: similar to chaperone proteins)

Answer 36

proteasomes!

Question 37

how do proteasomes work/function?

Answer 37

recycle/break down proteins! Hydrolyzes denatured protein back into its amino acids that can be used for generation of new proteins

Question 38

peroxisomes and what is their function?

Answer 38

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)

Question 39

what are glyoxysomes? found only in __?

Answer 39

Glyoxysome= variation of peroxisome. Convert lipids to carbohydrates for plant growth/germination (aka gluconeogenesis)! found only in plants!

Question 40

T/F: peroxisomes and glyoxysomes are derived from the golgi

Answer 40

false! they are derived from the ER!

Question 41

genetic disorder associated w peroxisome dysfunction?

Answer 41

ALD= in adolescence, one's personality may completely switch due to reasons that aren't psychiatric

Question 42

what is the plasma membrane/function?

Answer 42

Plasma membrane= Semi permeable barrier separating inside of cell from extracellular environment.

Question 43

T/F: complex molecules can diffuse across the plasma membrane

Answer 43

false: complex molecules need to be TRAFFICKED across the plasma membrane, unlike

Question 44

what is the cytoplasm? cytosol?

Answer 44

cytoplasm= everything inside the plasma membrane cytosol= fluid inside the cell. the site of many cellular processes

Question 45

what is one cool function of mitochondria aside from being the powerhouse of the cell?

Answer 45

An intrinsic pathway of apoptosis (cell suicide)

Question 46

the mitochondria is a ___ membrane structure

Answer 46

dual (2 layers)

Question 47

what is the mitochondrial matrix?

Answer 47

fluid component of mitochondria, interior of mitochondria.

Question 48

what are cristae? why is this good?

Answer 48

the result of the inner membrane of the mitochondria folding inward, allows for large surface area

Question 49

T/F: mitochondria does not have ribosomes or DNA. T/F: mitochondrial DNA is circular

Answer 49

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

Question 50

how do mitochondria replicate?

Answer 50

Replicate by binary fission based on cellular need!

Question 51

what are plastids? example of a plastid?

Answer 51

Plastids= class of organelles occurring only in plants and some protists ex. chloroplasts

Question 52

do chloroplasts have a genome? shape?

Answer 52

yes, and it's circular

Question 53

what are chromoplasts and their function?

Answer 53

Light harvesting pigment complexes make up bright colors of flower plants, attract pollinating insects.

Question 54

what are leucoplasts and function?

Answer 54

cousins of chloroplasts lol responsible for storage and breakdown of starch.

Question 55

central vacuoles functions? where are they found?

Answer 55

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

Question 56

what organelle can replicate independently from its host cell?

Answer 56

mitochondria