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Cell Membrane & Ion Transport - Coggle Diagram
Cell Membrane & Ion Transport
List the factors affecting
solute diffusion
across cell membranes
constant movement across cell membranes
O2 supply
cells derive nutrients from ECF
supply of substrate for cellular metabolism
removal of CO2, waste & active products
DIFFUSION
D: net movement of substance from region HIGH conc to LOW conc across SELECTIVELY PERMEABLE MEMBRANE
PASSIVE
random thermal movement of molecules
CONCENTRATION
GRADIENT
high to low
MEMBRANE
PERMEABILITY
cell membrane
selectively permeable
diffuse readily
fatty acids
steroid hormones
O2
CO2
diffuse slowly
ions (diffuse better due to carrier molecules)
proteins (lipid insoluble)
MEMBRANE
VOLTAGE
cell NEGATIVE INSIDE
compared to outside
cations attracted in
electrostatically
NET IONS FLUX is proportional to
electrical & concentration gradient
MOLECULAR
WEIGHT
smaller = faster
larger = slower
DIFFUSION
DISTANCE
limited to 100µm
MEMBRANE
SURFACE AREA
rate of diffusion
directly proportional
to membrane surface area
TEMPERATURE
rate of diffusion
directly proportional
to temperature
Identify the conditions necessary for
osmosis
& understand the differences between:
osmolarity
tonicity
osmotic pressure
OSMOSIS
D: diffusion of water across semi-permeable membrane from dilute area to more conc area
requires:
solute conc gradient
membrane permeable to water not solute
simple diffusion & aquaporins
OSMOLARITY
D: total number of dissolved particles per litre of solvent
1 osmole
D: gram molecular weight of substance divided by number of freely moving particles each molecule can liberate in a solution
units
mOsmol/litre
increased osmolarity...
substances which
dissociate
in water
means more dissolved particles
measured by
osmometer
TONICITY
D: the actual effect of a solution on living cells e.g RBC
comparative term ∴ no units
ISOTONIC
D: same osmolarity as plasma
condition in
healthy people
IV fluid supplements (300mOsmol/L)
= ISOTONIC to avoid RBC damage
HYPERTONIC
D: more osmotically active particles than ICF
osmotic water loss
cells
SHRINK
crenation
more conc soln than cell
HYPOTONIC
D: less osmotically active particles than ICF
osmotic cell SWELLING &
BURSTING
lysis
more dilute soln than cell
OSMOTIC PRESSURE
D: hydrostatic pressure needed to exactly oppose osmotic effect and prevent net movement
Describe the characteristics of carrier-mediated transport & differentiate between:
facilitated diffusion
primary active transport
secondary active transport
FACILITATED
DIFFUSION
method
carrier proteins cell membrane bind to specific substrate
shape/conformational change
substrate transported across mem
released other side
rate of transport increases as substrate increases
then levels off...
depends on
density of carriers
saturation occurs when all carriers occupied
passive = does not require ATP
driven by substrate concentration gradient
example
cellular absorption of glucose into RBC from extracellular fluid
PRIMARY ACTIVE
TRANSPORT
driven by ATP + requires carrier proteins
SODIUM-POTASSIUM PUMP
3 Na+ ions OUT
2 K+ ions IN
against conc gradient
method
3 Na+ and 1 ATP bind
intracellularly to protein carrier
ATP broken down to ADP
(hydrolysis)
conformational change in carrier protein
3 Na+ released outside
new confirmation
carrier protein binds 2 extracellular K+
phosphate released & 2 K+ transported into cell
role of Na+/K+ pump
control cell volume
SECONDARY ACTIVE
TRANSPORT
energy released during passive movement of 1 substance down gradient...
USED TO TRANSPORT another molecule AGAINST conc gradient
example
Na+ transport into intestinal cells coupled to glucose absorption
transport of substances across a cellular sheet
Na+ and water
diffuse
from lumen to cell interior
Na+
actively transported
into extracellular fluid
high Na+
gradient created
osmosis
of water occurs
Describe the process of endocytosis & exocytosis
ENDOCYTOSIS
TYPE 1
Receptor-mediate endocytosis
D: cellular uptake of ligands/molecules that bind to specific receptors
features:
clathrin-coated pits
vesicles
e.g. uptake LDL
cholesterol (insoluble) transported in blood bound to protein LDL
LDL binds to receptor on CM
receptor + LDL ingested by RME
some ppl non-functional LDL receptors
so build up cholesterol in blood
risk of atherosclerosis
mechanism
molecules attach to receptors on cell surface in coated pits
pits latticework of clathrin protein
membrane changes
pit invaginates inward
proteins close over
vesicle forms
process require ATP and Ca2+
TYPE 2
Phagocytosis
D: ingestion of large particles e.g. bacteria, whole cells, tissue pieces
only some cells capable
e.g. some blood cells
mechanism
CM receptors attach to surface of particle
membrane edges around attachment points
envaginates outward via pseudopods surround entire particle
ACTIN and contractile fibrils in cytoplasm...
surround vesicle & push to cell interior
process requires ATP & Ca2+
mechs
TYPE 3
Pinocytosis
D: ingestion of fluid and macromolecules or minute particles
occurs continually in most cell membranes
membrane folds inwards forming a vesicle containing extracellular fluid & solutes
vesicular transport
transport of substances within
MEMBRANE BOUND VESICLES
EXOCYTOSIS
mechanism
vesicle
fuses
with cell membrane
stimulated by
increased intracellular Ca2+ entry
in regulated exocytosis
involves
SNARE proteins
membrane's
outer surface opens
contents
extruded
e.g. release of neurotransmitters into synaptic cleft
