chapter 1 Flashcards
what does the plasma membrane allow
a cell to maintain homeostasis
does the interior or exterior environment have a higher potassium concentration
interior: higher potassium and lower sodium/calcium
what molecules cross the fastest over the plasma membrane
gases, other small hydrophobic molecules
what molecules cross at a medium speed over the plasma membrane
water
what does transport of water over the plasma membrane require
aquaporins
ex. of forms of communication between cells
receptors, signaling molecules
what molecules cross at a slow speed over the plasma membrane
ions (without channels or carriers)
facilitated diffusion
- when ions flow with the gradient (from high to low)
- requires ion channel proteins
what can ion channels be gated by
- ligands
- voltage
- temperature
gating
capacity to open/close ion channel
active transport
- if ions go against gradient (low to high)
- requires carrier proteins
- requires ATP
by which process does endosymbiosis occur
endocytosis - engulfing of particle
endosymbiosis theory
prokaryote might have been engulfed by a host cell (eukaryotic)
what about the nucleus, mitochondrion, and chloroplast resembles a prokaryotic cell
- the double membrane system surrounding them
- have genetic material and mechanisms to deal with it (replication, transcription, translation)
what do the ribosomes of mitochondria resemble
the ribosomes of bacteria/prokaryotes
problems with the endosymbiont theory
all cells use what for hereditary material
DNA
viruses use what for hereditary material
RNA and DNA
epigenetic inheritance
information passed on that is not carried in the DNA sequence
ex. of epigenetic inheritance
- proteins influencing others’ folding (prion proteins)
- centriole partner creation (always perpendicular to the existing one)
more genes in the human genome are devoted to what instead of the basic replication apparatus?
repairing DNA damage
mistakes that occur during replication are mostly caught by what?
DNA pol’s proofreading mechanism (3’ to 5’ exonuclease activity)
how are some mistakes that occur during replication repaired
mismatch repair pathway, acts immediately after replication
2 methods by which DNA damage occurs
- replication
- environmental effects
ex. of DNA damage caused by environmental effects
pyrimidine dimers - UV light
ex. of environmental effects
radiation, chemicals
how is DNA damage by environmental effects repaired
by several repair pathways, each with a specific problem they recognize
what happens when mistakes in DNA don’t get fixed
become mutations
what is the rate of mutation
very low, about one millionth of an event per gene per generation
what energy do mitochondria produce
ATP
anatomy of mitochondria
- 2 phospholipid bilayer
- matrix
- inter membrane space
- contains DNA
where does glycolysis always occur
cytoplasm - both proks and euks
3 processes involved in obtaining energy
- glycolysis
- Kreb’s cycle
- oxidative phsophorylation
what molecules does glycolysis produce?
ATP and NADH, pyruvate
where does the Kreb’s cycle occur in prokaryotes
cytoplasm
where does the Kreb’s cycle occur in eukaryotes
mitochondrial matrix
what does the Kreb’s cycle convert some of the energy from glucose into
ATP, NADH, FADH2
where do ETS and ATP synthase always occur
across a membrane
where does oxidative phosphorylation occur in prokaryotes
plama membrane
where does oxidative phosphorylation occur in eukaryotes
inner mitochondrial membrane
where are protons pumped during ETS?
from the matrix to the intermembrane space
what does the ATP synthase do
when protons flow through, converts ADP to ATP
anatomy of chloroplasts
two phospholipid bilayers, storm, inter membrane space, thylakoid membranes/spaces, DNA
ex. of biosynthetic reactions that plastids perform
nitrogenous base and aa synthesis
plastids develop from what?
undifferentiated proplastids
the type of plastids that develop from proplastids depends on what?
cell type
chloroplasts are a type of what?
plastid
what does chlorophyll provide
electrons, activated by light
how are chloroplasts differentiated
with chlorophyll and enzymes for photosynthesis
amyloplasts
- differentiated to synthesize and store starch
- stored as granules in stroma
- seeds/tubers
chromoplasts
- differentiated to contain various pigments
- synthesize/store carotenoids
function of nucleus
- gene expression proteins exported/imported
- RNA exported
function of endoplasmic reticulum
- protein modification
- proteins imported cotranslationally
function of Golgi apparatus
- protein modification
- proteins arrive by trafficking from ER
function of endosome
- sorting of internalized proteins for transport
- proteins that function in endoscopes are targeted from the secretory pathway
function of lysosome
- degradation of internalized proteins
- degradation of cytosolic proteins
function of mitochondrion
- energy handling
- proteins imported from cytosol
- some proteins synthesized in organelle
function of peroxisome
- oxidative processes
- proteins imported from cytosol
most proteins in an organelle were synthesized where?
cytosol
how are proteins directed to their final location
via signal sequences, must usually traverse a membrane at least once
what is the difference between protein transport for nuclei/peroxisomes and mito/chloro
- n/p: sorting signal, go through hydrophilic channel in a folded configuration
- m/c: transported through channel, kept unfolded before transport, refolded post-transport
how is a protein transported into the ER?
cotranslation
- nascent protein being synthesized on a ribosome has tsl halted until it goes to RER
- tsl resumes while translocation ensues as protein emerges from ribosome
once ribosome-membrane junction formed, what two outcomes can occur
- pass through membrane to lumen
- be incorporated is membrane
constitutive secretion of proteins
always transported out of all after they have been synthesized
induced secretion of proteins
released only when cell receives appropriate stimulus (specialized)
what kind of movement is exocytosis
anterograde
what kind of movement is endocytosis
retrograde
how do empty vesicles return lipids to earlier parts of pathway
by retrograde movement
each compartment has a ______ collection of proteins and lipids
unique
true or false: proteins need a new signal sequence for each compartment
true
what do chaperones require for activity
ATP
how do chaperones detect proteins that need to be folded
recognize immature conformation, typically hydrophobic regions that should aggregate in the center
when do chaperones help proteins get folded properly
- when first made
- after entering compartment
- after heat/stress to a cell
- also helps unfold proteins in preparation for translocation
when do most cytoskeletal fibers rearrange?
beginning of mitosis, meiosis, and telophase
what are microtubules mostly composed of
a-tubulin and B-tubulin dimers
diameter of microtubules
25 nm
largest cytoskeletal fiber
microtubules
smallest cytoskeletal fiber
microfilaments (actin filaments)
what are actin filaments made of
actin dimers
diameter of actin filaments
8 nm
what is actin filament movement powered by
ATP hydrolysis
polarity of actin subunits
ATP-binding site at one end connecting next subunit
