TUNPA Session 1: Physiology - Osmosis and Ion Equilibria

Questions and Answers

Osmotic pressure (π) is measured in what units?

units of atmospheres (atm) or millimeters of mercury (mm Hg).

What is 1 atm equal to?

760 mm Hg.

Define osmotic pressure.

It is the amount of pressure that must be applied to oppose osmosis.

How is osmolarity defined?

The number of particles per liter (osmol/L = OsM). Signup and view all the answers

Define molarity.

Moles/L. Signup and view all the answers

What is the dissociation constant?

1.8. Signup and view all the answers

What is the osmolarity of the human body?

280-296 milliosmoles/L (about 300 mOsM). Signup and view all the answers

How is osmotic pressure created by water?

By it moving down its concentration gradient. Signup and view all the answers

How is osmosis defined?

Water moving from a high concentration of water toward a lower concentration of water. Signup and view all the answers

What are the units of osmolality?

Osmols/kg. Signup and view all the answers

Is the ICF negatively or positively charged relative to ECF?

Negatively. Signup and view all the answers

Lipids function as what in the cell membrane in relation to transmembrane potential?

An insulator. Signup and view all the answers

The transmembrane potential at rest is also known as?

Resting potential. Signup and view all the answers

At about what value is the resting potential in most cells?

(-70mV). Signup and view all the answers

The Nernst equation is used to calculate what?

Equilibrium potential for a given ion. Signup and view all the answers

What is the equilibrium potential (Eion) for Na+?

(+60mV). Signup and view all the answers

What is the equilibrium potential (Eion) for K+?

(-87mV). Signup and view all the answers

What is the equilibrium potential (Eion) for Ca2+?

(+124mV). Signup and view all the answers

What is the equilibrium potential (Eion) for Cl-?

(-47mV). Signup and view all the answers

What is the equilibrium potential (Eion) for HCO3-?

(-12mV). Signup and view all the answers

What is the equilibrium potential (Eion) for H+?

(-12). Signup and view all the answers

What three molecules contribute to the cell membrane's resting potential in addition to impermeable ions and proteins?

Largely due to K+, and secondarily, Na+ and Cl-. Signup and view all the answers

Study Notes

Osmotic Pressure and Osmolarity

Osmotic pressure (π) is measured in atmospheres (atm) or millimeters of mercury (mm Hg).
1 atm is equivalent to 760 mm Hg.
Osmotic pressure is the pressure required to oppose water movement across a semipermeable membrane.
Osmolarity is defined as the number of particles per liter (osmol/L); it can be calculated using the formula: osmol/L = molarity (mol/L) x dissociation constant.
Molarity is expressed in moles per liter (moles/L).
The dissociation constant for common biological solutes is around 1.8.
The osmolarity of the human body typically ranges from 280-296 milliosmoles/L, approximately 300 mOsM.

Osmosis and Water Movement

Osmotic pressure is generated by water moving down its concentration gradient.
Osmosis is the movement of water from an area of high water concentration to an area of low water concentration.
Osmolality is measured in osmols per kilogram (osmols/kg).

Resting Membrane Potential

Intracellular fluid (ICF) is negatively charged relative to extracellular fluid (ECF).
Lipids act as insulators in the cell membrane, influencing transmembrane potential.
The resting transmembrane potential is also referred to as resting potential, typically around -70 mV.

Equilibrium Potential and Nernst Equation

The Nernst Equation is utilized to calculate the equilibrium potential (Eion) for a specific ion, represented as Eion = (61/z)(log([ion out]/[ion in])), where z is the ion's valence.
The equilibrium potential for specific ions is as follows:
- Sodium (Na+): +60 mV
- Potassium (K+): -87 mV
- Calcium (Ca2+): +124 mV
- Chloride (Cl-): -47 mV
- Bicarbonate (HCO3-): -12 mV
- Hydrogen (H+): -12 mV
The resting potential of cell membranes is primarily influenced by potassium (K+), with sodium (Na+) and chloride (Cl-) contributing secondarily.

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Description

This quiz explores key concepts in physiology related to osmosis, ion equilibria, and resting membrane potential. It features flashcards covering terms like osmotic pressure and osmolarity, providing a concise review of essential definitions and measurements. Ideal for students seeking to reinforce their understanding of physiological principles.