eukaryotic cells Flashcards
the function of the nucleus is to
contain and protect DNA, replication, transcription, splicing, and partial assembly of ribosome (2)
what surrounds the nucleus to separate the contents of the nucleus into distinct compartments?
nuclear envelope - which is compose of a lipid bilayer membrane
the genome is the sum total of
an organisms genetic information (chpt 4 notes)
the nuclear envelope contains pores that allow
passage of material in and out of the nucleus
the smaller molecules enter by what process through the nuclear envelope pores?
diffusion
the larger molecules enter by what process through the nuclear envelope pores?
they must have a nuclear localization sequence (basic amino acid sequence) so they can be translated on cytoplasmic ribosomes to be imported into the nucleus through specific transport mechanism
the nucleolus (contains no membranes) is a region within the nucleus that functions as a ribosome factory for
loops of DNA, RNA poly, rRNA, and protein components of the ribosome
the nucleolus is the site of?
transcription of rRNA by RNA poly I
the nucleolus is largest in cells that are producing?
large amount of protein - the increase of size reflects the increase of ribosome synthesis
the loops of DNA in nucleolus are used as a?
template for ribosomal RNA production
the mitochondria is the site of?
oxidative phosphorylation and produce ATP via the krebs cycle
the inner membrane of the mitochondria is the location of?
the electron transport chain and ATP synthase
the inner membrane of the mitochondria is impermeable to what type of substances?
polar substances
the folding of the inner membrane (cristae) increases what?
the surface area and allows for increased electron transport and ATP synthesis
the endosymbiotic theory suggests that mitochondria?
originated as independent unicellular organism living within larger cells because it possess their own genome that consists of single circular DNA molecules
mitochondria exhibit maternal inheritance which means that
if the female has a disease caused by an abnormality in her mitochondrial genome, her offspring will have that disease
the rough endoplasmic reticulum contains
a larger number of ribosomes bound to their surface
the ribosomes on the RER serve as the site of
protein synthesis for proteins that will enter the secretory pathways
proteins synthesized on RER have three types of pathways:
1) will be secreted into the extracellular environment
2) will be intergral for plasma membrane proteins
3) will be in the membrane or interior of ER, golgi apparatus, of lysosome
signal sequence of a polypeptide is recognized by a signal recognition particle (SRP) which then binds to a
ribosome
the signal sequence is when proteins have a specific
amino acid sequence at their N-terminus
once a polypeptide binds to a ribosome via SRP, the RER has what?
SRP receptor that binds the ribosome-SRP complex to the cytoplasmic surface
once an ribosome-SPR complex binds to cytoplasmic surface, what happens?
translation then pushes polypeptide into ER lumen (page 181)
transmembrane domains are?
hydrophobic amino acid residues found on the interior of integral membrane proteins
transmembrane domains on integral membrane proteins allow for the protein to
pass through lipid bilayer membrane and not removed during translation and are threaded through the ER membrane
targeting signals are needed for
protein traffic for proteins that need to end up elsewhere like the golgi, ER, or lysosome
localization signals are needed for
protein traffic for when proteins made in the cytoplasm need to be sent to an organelle that is not apart of the secretory path (e.g nucleus, mito, or peroxisomes)
the three functions of the golgi apparatus are
1) modification of proteins made in the RER; especially important is the modification of oligosaccharide chains
2) sorting and sending proteins to the their correction destinations
3) synthesizes certain macromolecules, such as polysaccharides to be excreted
the vesicle traffic to and from the golgi apparatus is mostly
unidirectional
*retrograde traffic if proteins escape
the portion of the golgi nearest to the RER is
cis stack
the portion of the golgi is the middle to the RER is
medial stack
the portions of the golgi furthest from the RER is
trans stack
the pathway of the vesicles from the ER is
cis to medial to trans, where each section has different enzymes where the vesicles are modified to be moved to the next
once the vesicles have left the golgi the are transported to the
cell surface and fuses with the cell membrane that the contents of the vesicles are released into the extracellular environment (exocytosis)
constitutive secretory pathway is when vesicles are
immediately sent from the golgi to the cell surface
regulated secretory pathway is when vesicles are
release at specific times in a response from a change in the extracellular membrane
SER function to
detoxification and glycogen breakdown in liver and steroid synthesis in gonads
RER function to
location of synthesis/modification of secretory, membrane-bound, and organelle proteins
lysosomes function to
degradation of biological macromolecules by hydrolysis by acid hydrolases enzyme
lysosome proteins are made in the ____, then modified in the _____ to be released
RER and golgi
lysosomes perform autophagy, which is
self-eating, when organelles have been damaged, they are degraded by the lysosome
ex: mitochondria
lysosomes perform phagocytosis, which is
cell-eating, when lysosomes degrade large particulate matter by engulfing cell
lysosomes perform crinophagy, which is
lysosomal digestion of unneeded/excess secretory products
after hydrolysis processes, the lysosomes will release
molecular building blocks into the cytoplasm for reuse
the enzyme lysosomes use for hydrolysis/degradtion is
acid hydrolases
the environmental pH of lysosomes is around
5, so that the acid hydrolases can be active
peroxisomes function to
metabolize lipids and toxins using H2O2
in the liver, peroxisomes help by
detoxification of drugs and chemicals
peroxisomes contain an enzyme called
catalase which converts H202 into H20 + 02
peroxisomes protect the rest of the cell from
peroxides and oxygen radicals
in the plasma membrane, integral membrane proteins are
embedded into the membrane by hydrophobic interactions - so that the hydrophilic head of the phospholipids are either on the top or bottom of it
in the plasma membrane, the transmembrane domains are
membrane crossing regions, where the domains take up an entire section of the membrane
in the plasma membrane, peripheral membrane proteins are
not embedded in the membrane but chill on the top or bottom of the hydrophilic head
equation for molarity (M)
moles of solute divided by #liters of solution
equation for molality (m)
moles of solute divided by #kg of solvent
electrolytes are free ions in a solution that
conduct electricity
strong electrolytes are solutes that
dissociate completely into solution
weak electrolytes are solutes that
dissociate partially into solution
van’t hoff factor (ionizability, i) states how many
ions one unit of a substance will produce in a solution
ex: NaCl = Na+ + Cl- i=2
CaCl2 = Ca2+ + 2Cl- i=3
colligative properties are dependent on the
number of solute particles in the solution rather than the type of particle
colligative properties include
vapor pressure depression
boiling point elevation
freezing point depression
diffusion/osmosis
vapor pressure depression is when the pressure exerted by
gaseous phase of a liquid that evaporated from the exposed surface of a liquid
in vapor pressure depression, the weaker the substance’s intermolecular forces,
the higher the vapor pressure thus easily evaporates
in vapor pressure depression, volatile liquids are those that are
easily vaporized thus have high vapor pressure
in vapor pressure depression, when a liquid contains a dissolved solute, the vapor pressure if effected by
solute molecules are attached to solvent molecules (anchors) thus more energy is require to enter gas phase
and adding more solute to solution will decrease its vapor pressure
the boiling point of a liquid is defined as the
temperature at which the vapor pressure of the solution is equal to the atmospheric pressure over the solution
in boiling point elevation, the more solute particles in the solution
the higher the BP
in freezing point depression, presence of solute particles interfere with
the arrangement of solvent molecules thus the liquid will have a decreases freezing point
diffusion is the tendency of
liquids and gases to fully occupy the available volume (high to low)
osmosis is the tendency of
solvents to diffuse rather than solutes
in osmosis, semipermeable membranes allow
water to pass but not other solute particles like sucrose
isotonic environment of a cell is when
the solute concentration is the same on the inside and outside
hypertonic environment of a cell is when
there are more total dissolved solutes than the cell (wrinkled cells)
hypotonic environment of a cell is when
there are less total dissolved solutes than the cell (swollen cells)
osmotic pressure is the pressure it would take to
stop osmosis from occuring
passive transport is when any
thermodynamically favorable movement of solute across a membrane where no energy is required
simple diffusion is when
diffusion of solute through a membrane with help from a protein
facilitated diffusion is when
movement of solute across membrane, down a gradient, when the membrane itself is intrinsically impermeable to that solute
channel proteins and channel carriers
facilitated channel proteins allow material that
cannot pass through the membrane by simple diffusion to flow through the plasma membrane down a concentration gradient
voltage-gated ion channels open in response to
change in the electrical potential
ligand-gated ion channels open in response to
binding of specific molecule (i.e. neurotransmitter)
facilitated carrier proteins bind to molecules being
transported to one side of the membrane and then undergo a conformational change to move the molecule to the other side
the facilitated carrier protein, uniports transport
only one molecules
facilitated carrier protein, symports transport
two substances
facilitated carrier protein, antiports transport
carry two substances in opposite direction of gradient
eukaryotes do not contain pores in the membrane because
pores destroy the barrier function of the membrane and allow solutes in the cytoplasm to freely diffuse out of the cell
active transport is the movement of
molecules through membrane against a gradient that requires energy and proteins
in primary active transport the molecule being transported is
coupled to ATP hydrolysis
in secondary active transport the molecule being transported is
not directly coupled to ATP hydrolysis but rather the ATP is used first to created a gradient, then the potential energy is used to drive the transport
the sodium potassium pump is a
transmembrane protein in the plasma membrane that pumps 3 sodium (Na+) out of the cell and 2 potassium (K+) into the cell
the purpose of 3 sodium out and 2 potassium in, is to
hydrolyze one ATP to drive the pumping of these ions against their gradients
once sodium has been pumped out they cannot return because
the membrane is impermeable to sodium ions
potassium leak channels allow for
potassium ions that have been pumped into the cell to leak out depending on concentration gradient
resting membrane potential drives secondary active transport because
as K+ leak from the cell, the movement of positive charge out of the cell creates an electric potential across the membrane with a net negative charge on the inside of cell
the main purposes of the sodium potassium ATPase (pump) is to
maintain osmotic balance between the cell’s inside and outside
establish the resting membrane potential
provide the sodium concentration gradient used to drive secondary active transport
mnemonic: life evolved in the ocean, which has high concentrations of NaCl, thus the concentrations of
Na+ and Cl- are high outside the cell and low inside the cell
exocytosis is the process to transport material
outside of a cell in which a vesicle in the cytoplasm fuses with membrane and the content of the vesicle expelled into extracellular space
endocytosis is the process in which materials are
taken into the cell by invagination of a piece of membrane to form a vesicle (endosome)
*3 types of endocytosis
the first type of endocytosis is, phagocytosis which is
cell eating where there is an uptake of large particulate matter into a phagocytic vescile, which later merges with a lysosome
the second type of endocytosis is, pinocytosis which is
cell drinking where a nonspecific uptake of small molecules and extracellular fluid via invagination
the third type of endocytosis is, receptor-mediated endocytosis which is
site of endocytosis is marked by pit coated with clathrin (inside) and with receptors that bind to specific molecules (outside)
ex: cholesterol in the blood where if they are not removed they build into the walls of the arteries
cell surface receptors bind through what type of mechanism?
lock and key
the key component for a receptor is termed a
ligand
signal transduction is when
a ligand is binding to its receptor on the extracellular surface of the plasma membrane that triggers a response within the cell
ligand-gate ion channels are
channels that open upon the binding of a particular neurotransmitter
ex: when Ach binds, the receptor has confirmational change to become a sodium channel resulting in massive influx of Na+ to depolarize to muscle cell to contract
catalytic receptors are
enzymatic active sites on cytoplasmic side of the membrane
the main protein is kinase, which is an enzyme that binds phosphate groups to proteins
G-protein-linked receptors
associated with an intracellular protein that binds and hydrolyses GTP. When GTP is bound, the protein is active, and can regulate the activity of adenylyl cyclase; this modifies the intracellular levels of the second messenger cAMP. When the GTP is hydrolyzed to GDP, the protein become inactive again
what provides structural support via cell wall in bacteria, plants, and fungi?
cytoskeleton
what are the three types of internal cytoskeleton in animal cells?
microtubules, intermediate filaments, and microfilaments
what two globular proteins are microtubules made of?
alpha-tubulin and beta-tubulin that form alpha beta- tubulin dimer
what can microtubules only elongate at one end?
one side of the microtubule is anchored to the microtubule organizing center (MTOC) located near the nucleus
within each MTOC is a pair of centrioles, which duplicate themselves during?
cell division, duplicate and move to each end of the cell - in mitosis the microtubules radiating out from the centrioles attach to the replicated chromosomes and pull apart to be copied
MTOC are essential for mitosis but centrioles are not because
plant cells lack centrioles but still undergo mitosis
experiments have removed centriole and still have cells undergo mitosis
microfilaments are rods formed in the cytoplasm from polymerization of the globular protein?
actin
microfilament are essential for what function of the cell?
gross movement of entire cell, such as pinching and dividing parent cell into two daughter cells during cell division
and ameoboid movement (cell flowing in one direction)
tight junctions form seals between cells that prevent the
movement of substances across the cell layer
they are bands running all around the cells
tight junctions are found where in the body?
between the epithelial cells lining the intestines and between the cells forming the capillaries in the brain (blood-brain barrier)
desmosomes are used in epithelial cells in the skin to
tightly hold together cells but not forming a complete seal
desmosomes are concise points around the cell which are anchored to the plasma membranes of two cells by the protein
keratin
gap junctions are pore like connections between adjacent cells that allow two cells’ cytoplasms to mix to permit the exchange of
ions, amino acids, and carbohydrates
NOT polypeptides or organelles
gap junctions are located where in the body?
smooth and cardiac muscles to allow membrane depolarization of an action potential to pass directly from one cell to another
oncogenes are mutated genes that
cause cancer by converting normal cells into cancerous ones
