Transcript Electrolytes

Electrolytes
Biology
Electrolytes
• Free moving ions in a solution that conduct
electricity
– Galvanic cell converts chemical energy into
electrical
– Electrolytic cell – converts electrical energy into
chemical
Biological concepts related to ions
• Fluid balance
• Photosynthesis/ respiration
– Electron transport system
• Membrane potential
• Oxidation reduction reactions
Terms
• Flow of electrons (ions) from one region to
another is driven by a difference in potential
energy
• Voltage: difference in electrochemical
potential energy between two electrodes (V)
– Does not depend on size of the electrodes or
amount of materials. AAA, AA, A all have 1.54 V
– All our cells have -90mV
• Current: the rate of electron flow (amps)
Major electrolytes
• Taken as minerals (along with vitamins)
• Several of them are needed for proper function of
enzymes (cofactors)
• As for your body, the major electrolytes are as follows:
–
–
–
–
–
–
–
–
sodium (Na+) - depolarization
potassium (K+) - repolarization
chloride (Cl-) – balancing the charges
calcium (Ca2+) – trigger muscle contraction
magnesium (Mg2+) bicarbonate (HCO3-) – acid/base
phosphate (PO42-) - bones
sulfate (SO42-) - bones
Electrolytes and Water Balance
• Pure water vs electrolytes
• cells need to be bathed in fluids — inside and out.
• the current enables electrolytes to regulate how and where fluids
are distributed throughout the body, which includes keeping water
from floating freely across cell membranes.
– Water follows the charged ions
• help maintain a state of fluid balance.
• transport nutrients into cells and wastes out of them.
• The difference in electrical balance inside and outside of cells also
allows:
–
–
–
–
for transmission of nerve impulses,
contraction or relaxation of muscles,
blood pressure control, and
proper gland functioning.
Sodium levels
• 136 and 145 milliequivalents per liter (mEq/L) of sodium
• Sodium plays a key role in your body. It helps maintain normal
blood pressure, supports the work of your nerves and muscles, and
regulates your body's fluid balance.
• Hyponatremia: When the sodium levels in your blood become too
low, excess water enters your cells and causes them to swell.
Swelling in your brain is especially dangerous because the brain is
confined by your skull and unable to expand.
• Hypernatremia, the body contains too little water for the amount of
sodium. The sodium level in blood becomes abnormally high when
water loss exceeds sodium loss, as typically occurs in dehydration,
typically causes thirst. The most serious symptoms of
hypernatremia result from brain dysfunction, confusion, muscle
twitching, seizures, coma, and death.
Water and Mineral Availability
Only minerals dissolved in water in spaces among
soil particles are available
-Organic soil particles tend to have negative
charges, and so attract positive ions
-Therefore, active transport is needed to
move positive ions into root hairs
8
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1. Soil particles tend to
+
–
+
have a negative charge.
+
+
–
–
+
–
–
–
Soil particle
+
–
–
–
+
–
–
+
–
ATP
–
–
+
–
+
+
–
+
–
2. Positive ions are
attracted to soil particles.
+
+
3. Negative ions stay in
+
–
–
–
Root hair
+
+
solution surrounding
roots, creating a charge
gradient that tends to
“pull” positive ions out
off the root cells.
+
4. Active transport is
Water
required to acquire and
maintain K+ and other
positive ions in the root.
9
Plant Nutrients
Plants require a number of inorganic nutrients
-Macronutrients: Used in relatively large
amounts
-Nine = C, O, H, N, K, Ca, Mg, P & S
-Micronutrients: Used in minute amounts
-Seven = Cl, Fe, Mn, Zn, B, Cu & Mo
A deficiency of any one can have severe effects on
plant growth
10
Plant Nutrients
11
Responses to Mechanical Stimuli
http://plantsinmotion.bio.indiana.edu/plantmotion/m
ovements/nastic/mimosa/mimosa.html
(animation of plant response)
Mimosa pudica leaves have swollen structures called
pulvini at the base of their leaflets
-When leaves are stimulated, an electrical signal is
generated
-Triggers movement of ions to outer side of
pulvini
-Water follows by osmosis
-Decreased interior turgor pressure
causes the leaf to fold
12
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Leaflet blade
Pulvinus
Vascular tissue
Petiole
a.
Cells gaining turgor
b.
Cells losing
turgor
Cl–
K+
H2 O
13
Carnivorous Plants
Often grow in acidic soils that lack nitrogen
-Trap and digest small animals, primarily
insects, to extract additional nutrients
-Have modified leaves adapted for
luring and trapping prey
-Prey is digested with enzymes
secreted from specialized glands
14
15
The Rate of Transpiration
Guard cells have thicker cell walls on the inside
and thinner cell walls elsewhere
-This allows them to bulge and bow outward
when they become turgid
-Causing the stomata to open
Turgor in guard cells results from the active uptake
of potassium (K+), chloride (Cl–), and malate
16
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Tied end
Slightly inflated balloon
“Stoma”
Add turgor
pressure (air)
Add thickened inner walls
(overlapping duct tape)
17
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Closed stoma:
flaccid guard cells
Little water in vacuole
Open stoma:
turgid guard cells
H2O
K+
Malate2–
Cl–
H2O
H2O
Vacuole filled with water
18
The Rate of Transpiration
Closed stoma:
flaccid guard cells
Open stoma:
turgid guard cells
H2O
K+
H2O
Cl–
H2O
Malate2–
H2O
K+
H2O
Cl–
H2O
Malate2–
ABA
K+
K+
H2O
H2O
Cl–
Cl–
H2O
H2O
ABA
Malate2–
ABA
K+
H2O Cytosol
H2O
Cl–
Malate2–
H2O
K+
H 2O
Malate2–
Cytosol
H2O
Cl–
H2O
Malate2–
ABA
ABA
19
Water Stress Responses
Plants, such as mangroves, that grow in salt water
produce pneumatophores
-Long, spongy, air-filled roots, that emerge
above the mud
-Have large lenticels through which
oxygen enters
-These plants also secrete large quantities of
salt
20
Water Stress Responses
21
Water Stress Responses
Plants called halophytes live in saline soil
-Produce high concentrations of organic
molecules in their roots
-This decreases the water potential
enhancing water uptake from the soil
22
Humans and Electric shock
• 1mA – sense the shock
• 10-20mA “knocked across the room” or “can’t
let go” effect – muscle contract and propelling
them
• 100-300 mA – irregular uncoordinated heart
beat disrupts overall pattern of the heart beat
• Defibrillator – 6A – continuous ventricular
contraction and respiratory paralysis
• Everything stops – back to normal heart beat
Frequency effect
• 60 Hz – same as firing frequency of nerves
• Humans are most sensitive and is most
dangerous frequency
Resting membrane potential
• Bioelectricity
– Slight differences in ion concentrations
– Inside more negative
– Outside more positive
– Difference -80mV
– Concentration gradient - electrical potential
– Coulombs force
Action potential
• Depolarization
• Repolarization
Fig. 8.10
Fig. 8.9
Fig. 8.18
Fig. 12.14
Fig. 12.15
Fig. 12.16