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58 Cards in this Set

  • Front
  • Back
Passive Transport
any thermodynamically favorable
movement of solute across a
membrane
Simple diffusion
diffusion of a solute through a
membrane without help from a
protein
Plasma membrane is a barrier to
movement of all large and/or
hydrophilic solutes
Facilitated Diffusion
movement of a solute across
a membrane down a gradient
when the membrane is impermeable
to the solute
Channel and Carrier proteins
give the membrane
selective permeability
Gated channels
ion channels that open in
response to a specific
environmental stimuli
Voltage-gated ion channel
opens in response to a change in
the electrical potential across
a membrane
Ligand-gated ion channel
opens in response to binding of
a specific molecule like a
neurotransmitter
Ion channels are only involved
in
facilitated diffusion, movement
down an electrochemical
gradient
Carrier proteins
bind to molecule to be
transported on one side of
membrane and undergo a
conformational change to move
the molecule to the other side
Pore
tube through the membrane
which is so large that it is not
selective for any particular
molecule, eukaryotic plasma
membranes do NOT contain them
Rate of Simple Diffusion limited
by
surface area of the membrane and
the size of the gradient
Rate of Facilitated Diffusion
limited by
the finite number of integral
membrane proteins, exhibits
saturation kinetics
Active Transport
movement of molecules through
the plasma membrane against
a gradient, requires energy
input
Primary Active Transport
transport of a molecule is
coupled to ATP hydrolysis
Secondary Active Transport
transport not coupled directly
to ATP hydrolysis, but to the
flow of an ion down its
electrochemical gradient
(commonly Na ions), glucose
transport
Na+/K+ ATPase
transmembrane protein in the
plasma membrane of all cells
in the body
- pumps 3 Na+ out of cell and
2 K+ into cell and
hydrolyzes 1 ATP
- establishes resting membrane
potential
Potassium Leak Channels
potassium ions pumped into the
cell are able to leak out, down
its concentration gradient,
sodium ions cannot flow back
into cell
Resting membrane potential
potential created by
Na+/K+ ATPase, net negative
charge on the interior of cell,
-70mV
Na+/K+ ATPase important in 3
ways:
1) to maintain osmotic balance
between the cellular interior
and exterior
2) to establish resting
membrane potential
3) to provide sodium
concentration gradient used to
drive secondary active
transport
Ions with higher EXTRACELLULAR
concentrations than
intracellular concentrations:
Na+, Cl-, Ca2+
Ions with higher intracellular
concentrations than
extracellular concentrations:
K+
Exocytosis
process to transport material
outside of cell in which a
vesicle in cytoplasm fuses with
plasma membrane and contents of
vesicle expelled, ex. hormones
and digestive enzymes
Endocytosis
materials are taken into cell
by an invagination of a piece
of cell membrane to form a
vesicle (endosome)
3 types of endocytosis:
1)phagocytosis
2)pinocytosis
3)receptor-mediated endocytosis
Phagocytosis
nonspecific uptake of large
particulate matter into a
phagocytic vesicle which later
merges with a lysosome, ex.
macrophages
Pinocytosis
nonspecific uptake of small
molecules and extracellular
fluid
Receptor-mediated endocytosis
very specific, binding of a
specific molecule via receptors
, ex. cholesterol uptake from
the blodd
3 main types of signal-
transducing cell surface
receptors
1) ligand-gated ion channels
2) catalytic receptors
3) G-protein linked receptors
Ligand-gated ion channels
open an ion channel upon binding
of a particular neurotransmitter
Catalytic receptors
have an enzymatic active site
on cytoplasmic side of membrane
and initiated by ligand binding
at extracellular surface, ex.
protein kinases
G-protein linked receptor
does not directly transduce its
signal, but transmits it via
a second messenger, binds GTP
Second messengers
allows for a much greater signal
than receptor alone via cascade
amplification, ex. cAMP- second
messeger for hormone glucagon
and epinephrine (universal
hunger signal)
Stimulatory G-protein linked
receptors
activates adenylyl cyclase,
which forms more cAMP and
further cascade
Inhibitory G-protein linked
receptors
inactivates adenylyl cyclase,
less cAMP
G-protein linked receptors and
phospholipase C
different second messenger
cascade, activates phospholipase
C, causing an increase in
cytoplasmic Ca2+ levels
Cytoskeleton composed of
3 proteins:
1)microtubules
2)intermediate filaments
3)microfilaments
- quartenary protein structure
Microtubules
hollow rod composed of two
globular proteins, alpha and
beta tubulin, also assist in
transport of substances within
cell
Microtubule organizing center
(MTOC)
located near nucleus,
microtubules elongate from here,
contains centrioles
- MTOC essential for mitosis,
but not centrioles
Cilia
small hairs on the cell surface
which move fluids past the cell
surface
Flagellum
large tail which moves the cell
by wiggling
Both cilia and flagella have:
9+2 arrangement,
9 pairs of microtubules
surrounding 2 lone microtubules
in the middle, each connected
to each other by dynein
Microfilaments
rods formed in the cytoplasm
from actin polymerization,
dynamic, responsible for gross
movements of entire cell
Intermediate filaments
in between thickness,
heterogeneous composition of
polypeptides unlike microtubules
and microfilaments,
-permanent (microfilaments and
microtubules are often
assembled and disassembled)
Tight junctions
form a seal between the
membranes of adjacent cells that
blocks the flow of molecules
across the entire cell layer
Apical surface
surface of the plasma membrane
facing the intestinal lumen
Basolateral surface
plasma membrane on the other
side of the cell facing the
tissues beneath
Desmosomes
do not form a seal, but hold
cells together at spots
Gap junctions
form pore-like connections
between adjacent cells, allowing
the two cells cytoplasms to mix,
large enough to permit the
exchange of solutes such as
ions, amino acids, and
carbohydrates
-allows membrane
depolarization of an action
potential to pass between
cells in smooth muscle and
cardiac muscle
Interphase
G1, S, and G2 phases,
- cell spends most of time in
this phase
- blood cells, neurons, and
cells on surface of skin are
permanently in interphase
-not visible with light
microscope without special
stains
-(2n*2) chromosomes
Mitosis stages:
1)prophase
2)metaphase
3)anaphase
4)telophase
Mitosis phases:
1)prophase
2)metaphase
3)anaphase
4)telophase
Prophase
chromatin densely packed into
chromosomes
-visible under light microscope
-nucleolus disappears
-spindle appears
-centrioles migrate to
opposite ends of cell
-23 homologous pairs of
chromosomes
Sister chromatids
identical copies of a
chromosome attached to each
other at the centromere
Homologous chromosomes
equivalent but nonidentical
and do not come anywhere near
each other during mitosis
Metaphase
all the chromosomes line up
at the center of the cell
forming the metaphase plate
Anaphase
spindle fibers shorten and the
centromeres of each sister
chromatid pair are pulled apart,
cell elongates, cytokinesis
begins
Telophase
a nuclear membrane forms around
the bunch of chromosomes at
each end of the cell,
chromosomes decondense,
nucleolus becomes visible
-2n chromosomes
-cytokinesis complete
-cell split in two