exam 2 (review slides) Flashcards
what is cell fractionation? how does it work? how are pellets separated based on size? and what is a supernatant?
cell fractionation: takes cells apart and separates major organelles and other cell structures from one another
- done using a centrifuge, tube that spins really fast - components of cell settle at the bottom, forming a pellet
- higher speed = pellet w smaller components
- lower speed = pellet w larger components
supernatant: rest of the liquid which is at the top (consists of lighter components that didn’t settle at the bottom - i.e. cytoplasm & other small cell parts)
prokaryotic cells are characterized by having:
- no nucleus
- no membrane bound organelles
- DNA in an unbound region called nucleoid
- cytoplasm bound by plasma membrane
eukaryotic cells are characterized by having:
- DNA in a nucleus that is bounded by a double membrane
- membrane bound organelles
- are also much larger than prokaryotic cells
nucleolus
- site of ribosomal RNA (rRNA) synthesis
- assembles and produces ribosomes
- “command center” inside the nucleus
function of the nucleus
- control center
- hold’s cell’s genetic information
- DNA replication, transcription, and translation happen here
translation vs transcription
- transcription: synthesizing RNA from DNA
- translation: synthesizing proteins fro the RNA
function of ribosomes + 2 types
“protein factories” - site of protein synthesis
free ribosomes: most proteins made on free ribosomes function within cytosol (free ribosomes are not attached to the ER)
bound ribosomes: make proteins destined for insertion into membrane, for packaging within organelles, or for export out of cell (bound to the ER)
what is the endoplasmic reticulum + the 2 types
- cell’s “highway”
- membrane of interconnected tubules that carry stuff around the cell
two types:
rough ER: synthesis and packaging of proteins
- bumpy because ribosomes are attached to it
- also distributes transport vesicles
smooth ER: has enzymes that help create and package lipids and also detoxifying substances and stores calcium ions
order of where the proteins go after synthesis
- membranes & proteins produced by the ER move via transport vesicles to the Golgi
- The Golgi pinches off transport vesicles and other vesicles that give rise to lysosomes, other types of specialized vesicles, and vacuoles
- The plasma membrane expands by fusion of vesicles; proteins are secreted from the cell by exocytosis
what are the 3 destinations for proteins produced by the rough ER
- shipped to another organelle (enzymes to catalyze reactions)
- inserted into plasma membrane (membrane transporters or pumps)
- secreted outside of cell (carry messages to other cells - glycoproteins)
what are transport vesicles
helps move materials, especially proteins from one organelle to another
- distributed by the rough er
function of glycoproteins
enable cells to recognize another cell as familiar or foreign, which is called cell-cell recognition
cis and trans Golgi apparatus
cis: means same
- part of the Golgi apparatus nearest to ER (endoplasmic reticulum), functions primarily in receiving and sorting molecules
trans: means opposite
- part of Golgi farthest from ER, functions in final modifications of proteins before they’re shipped out`
what is the function of the Golgi apparatus?
“post office of cell city”
- processes proteins + packages them before sending them where they need to go via transport vesicles
what are vesicles
sacs that little goodies are packaged into
- used to ship stuff within cell or outside cell
what are lysosomes?
sacs of enzymes that break down cellular waste and debris from outside cell to turn into simpler components for inside cell
- “digestive system of cell”
- membraneous-enclosed sac of hydrolytic enzyme that can digest macromolecules
what is autophagy?
lysosomes use enzymes to recycle the cell’s own organelles and macromolecules
what is the function of the mitochondria?
cellular respiration!
- use oxygen to generate ATP
- cells that need more power (such as muscle cells) have more mitochondria in them
what is the inheritance pattern for mitochondria?
maternal b/c mitochondria self replicates so DNA never mixes with the father’s
what is unique about mitochondria compared to other organelles?
acts like its own cell, does its own replication and even has some DNA
3 similarities between mitochondria and chloroplasts
- enveloped by a double membrane
- contain free ribosomes and circular DNA molecules
- grow and reproduce somewhat independently in cells
function of the chloroplasts
also energy!!
- sites of photosynthesis
- found in plants and algae
endosymbiont theory
idea that some organelles inside eukaryotic cells (like mitochondria and chloroplasts) were once independent, free-living bacteria
- bacteria engulfed by larger cells, instead of being digested, formed mutually beneficial relationship with the host cell
- over course of evolution, host cell and its endosymbiont merged into a single organism
2 main parts of a chloroplast
thylakoids: membranous sacs that capture light to turn into ATP solar panels of the cell
- stack to form granum
stroma: internal fluid that contains enzymes to use chemical energy to produce sugar kitchen of the cell, uses products to assemble
do plant cells have mitochondria?
yes, they have both mitochondria and chloroplast (chloroplasts are used for photosynthesis only)
how are mitochondria and chloroplasts similar?
- both have double-membrane
- have their own DNA and manufacture ribosomes
- grow and divide independently of cell division
- energy producing organelles
photosynthesis (chloroplasts) vs. cellular respiration (mitochondria)
- photosynthesis builds glucose by capturing energy from the sun and stores the glucose for later use
- cellular respiration breaks down glucose to ATP and for use within the cell
cilia and flagella
microtubule containing extensions that project from some cells
cilia: present in lung + throat cells to push up mucus
flagella: present in sperm cells
protozoans move around using cilia and flagella
tight junctions, gap junctions, and desmosomes (anchoring junctions)
tight junctions: “cellular zippers,” connect neighboring tissues tightly to make sure there are no leaks
- ex. present in digestive tract
gap junctions: “communication tunnels,” allow quick communication through openings that allow molecules and ions to pass directly
- ex. present in heart cells
desmosomes: fasten cells together into strong sheets, important in tissues subjected to mechanical stress, like skin and heart muscles
factors that affect membrane fluidity (3 factors + give reasons for why)
- membranes with more unsaturated fatty acids are more fluid (because of the kinks, they cannot pack together as closely)
- as temperature cools, becomes less fluid and more solid
- cholesterol molecules embedded in membrane - reduce fluidity but prevent total tight packing (helps because when you reduce temperature, membrane won’t solidify as quickly)
membranes must be fluid to work properly
membranes are held together by ___________________ bonds
weak hydrophobic
phospholipids form main fabric of membrane, but ________ determine most of membrane’s functions
proteins
- protein composition of membranes varies among cells within an organism, and among intracellular membranes within a cell
_____________ & ____________, _____________ molecules can enter the membrane easily
small & nonpolar, hydrophobic
how does the polarity of a molecule affect its crossing of the cell membrane?
- nonpolar molecules are hydrophobic and have easy time passing through
- polar molecules are hydrophilic and have difficulty passing (get stuck) or pass really slowly (including water)
proteins that are built into the membrane can help certain things pass
passive transport vs. active transport
passive transport: diffusion of substance across membrane with no energy required, goes down concentration gradient (high to low)
active transport: requires energy to move substances, movement against concentration gradient (low to high)
- if 2 substances in a solute, moves down its OWN concentration gradient, not the overall concentration gradient
2 things that the selective permeability of a membrane is dependent on
- natural permeability of a lipid bilayer (i.e. polar and nonpolar)
- specific transport proteins built into the membrane
osmosis
diffusion but basically only for water
- high to low water concentration
- low to high solute concentration
sodium-potassium pump + ratio of Na and K
- example of active transport
- exchanges sodium for potassium against the electrochemical gradient
- pumps sodium ions out and potassium ions in
- ATP is hydrolyzed to ADP
- carrier protein changes conformational shape
- 3 Na+ into cell, 2 K+ out
electrogenic pump
an active transport protein that generates voltage across a membrane while pumping ions
- in animals, it is Na+/K+ pump