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.

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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

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1. Soil particles tend to have a negative charge.

2. Positive ions are attracted to soil particles.

3. Negative ions stay in solution surrounding roots, creating a charge gradient that tends to “pull” positive ions out off the root cells.

4. Active transport is required to acquire and maintain K+ and other positive ions in the root.

Root hair

Soil particle

Water

ATP

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+

++

+

+

++

++

+

+

++

++

+

+

+

–

–

–––

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–

–– – –

–

–

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–

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–

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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

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Plant Nutrients

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Responses to Mechanical Stimuli

http://plantsinmotion.bio.indiana.edu/plantmotion/movements/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

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a.

b.

Pulvinus

Vascular tissue

Leaflet blade

Petiole

Cells losingturgor

Cl–

K+

H2O

Cells gaining turgor

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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

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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

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Slightly inflated balloon

Tied end

Add turgorpressure (air)

Add thickened inner walls(overlapping duct tape)

“Stoma”

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Closed stoma:flaccid guard cells

Open stoma:turgid guard cells

K+ Cl–Malate2–

H2O

H2OH2O Vacuole filled with water

Little water in vacuole

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The Rate of TranspirationClosed stoma:

flaccid guard cellsOpen stoma:

turgid guard cells

Cytosol Cytosol

ABA

ABAABA

ABA

ABA

H2O

H2O

H2OK+

Cl–

Malate2–

H2O

H2O H2O

H2OH2O

H2O H2O

H2O

H2O

H2OK+

K+ K+

Cl–

Cl– Cl–

Malate2–

K+

Cl–

Malate2–

Malate2– Malate2–

H2O

H2O

H2O

K+

Cl–

Malate2–

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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

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Water Stress Responses

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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

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