Chapter 6: Physical Equilibria Flashcards
Purpose of this chapter?
In this chapter, we focus on the thermodynamics
underlying the different concentrations of molecules among different regions of a system/ focus on the thermodynamics of different molecule concentrations within various parts of a system.
Understanding how molecules distribute in different compartments helps explain cellular reactions, transport mechanisms, and overall system behavior.
What are some examples of regions within a system where variations in molecule concentrations can occur?
Cell compartments separated by membranes, the inside
and outside of a membrane, a liquid or solid in contact with a gas, and (maybe mixture of) two immiscible
liquids.
What is the significance of chemical potential in understanding the distribution of molecules within a system?
Chemical potential (partial molar free energy) is significant because it indicates whether different compartments (2 or more) in a system are in equilibrium with one another. If the chemical potential is the same in all compartments, they are in equilibrium. If it differs, it signifies unequal concentrations and lack of equilibrium between compartments.
How does the concept of chemical potential help determine whether different compartments in a system are in equilibrium or not?
Chemical potential helps determine equilibrium by indicating whether the chemical potentials are equal or unequal in different compartments. Equal chemical potentials signify equilibrium, while unequal chemical potentials indicate a lack of equilibrium.
If a species has different chemical potentials in two phases, what direction will it move, and what will happen until equilibrium is reached?
This simple idea allows us to distinguish and characterize what?
- If a species has a different chemical potential in two phases, it will move from the phase with higher chemical potential to the phase with lower chemical potential until equilibrium is reached / The species will move from the phase with higher chemical potential to the phase with lower chemical potential. This movement continues until equilibrium is reached, at which point the chemical potential becomes the same in all phases.
- active and passive transport in cells, the equilibrium concentrations of molecules separated by
semipermeable membranes, and the equilibria of molecules between solids, liquids, and
gases that determine freezing points, solubilities, boiling points, and osmotic pressure.
What role does chemical potential play in determining equilibrium concentrations of molecules separated by semipermeable membranes?
Chemical potential differences across semipermeable membranes drive the movement of molecules until equilibrium is achieved, balancing the concentrations on both sides of the membrane.
What is the role of membranes in living cells?
- Membranes act as protective barriers, separating the interior of a cell from its external environment. They also permit controlled transport of molecules and signals between the inside and outside of the cell.
- These membranes, often made up of lipid bilayers containing proteins and other molecules that serve as recognition sites, signal transmitters, and ports of entrance and exit.
- They are extremely thin and are considered two-dimensional phases due to their minimal thickness, often just one or two molecules thick.
The thermodynamic properties of membranes are described in terms of? What is their significance?
Surface properties, such as surface chemical potential, surface tension, or pressure.
These properties are crucial because membranes not only separate cellular compartments but also facilitate the controlled transport of molecules and signals between the inside and outside of the cell.
Surface chemical potential, surface tension, and pressure are essential in describing the behavior of membranes. Surface chemical potential indicates the potential energy of molecules at the surface, surface tension reflects the energy required to increase the surface area, and pressure influences the shape and stability of membranes.
What do differences between the inside and outside of a cell influence?
Differences between the inside and outside of a cell influence the exchange
of metabolites and electrical signals, the flow of heat, and changes in shape.
In what ways do temperature differences, pressure variances, and electrochemical potential differences affect cellular processes ?
Temperature differences cause heat flow, pressure differences cause changes in shape, and electrochemical potential differences cause molecular transport and electrical signals.
Describe the concept of ligand binding in biological systems.
Ligands are molecules that bind to specific receptors or proteins in cells. The interaction between ligands and their binding sites, like oxygen (O2) binding to hemoglobin or substrates binding to enzymes, is essential for various processes in living cells.
What forces bind ligands to their respective receptors?
noncovalent interactions, which are weak chemical bonds
How do scientists experimentally measure ligand binding? ((The process by which small molecules (ligands) attach to larger molecules (macromolecules) in biological systems))
They use what’s known as Equilibrium dialysis. Equilibrium dialysis provides a method of exploring the binding between macromolecules and small ligand molecules.
Equilibrium dialysis involves using a semipermeable membrane. This membrane has tiny pores that allow small molecules (ligands) to pass through but restrict the movement of larger molecules (macromolecules). This membrane separates two compartments.
Purpose: The goal is to establish equilibrium between two phases separated by the membrane. One phase contains the macromolecule, and the other contains the ligand.These two molecules interact with each other.
Process: The ligand moves through the membrane, attempting to reach an equilibrium concentration in both phases./ The semipermeable membrane allows the ligand to move back and forth between the compartments. Over time, the ligand molecules will move through the membrane until the rate at which they move from one side to the other equals the rate at which they move back. This state, where the movement of ligand molecules between the compartments is balanced, is called equilibrium.
Concentration Differences: The concentration of the ligand on each side of the membrane depends on how strongly it interacts with the macromolecule. If a strong interaction occurs, there will be a significant difference in ligand concentration between the two phases.
Usefulness: By studying these concentration differences, scientists can determine the equilibrium binding constants. These constants quantify how tightly the ligand and macromolecule are bound together./The concentrations of the ligand on both sides of the membrane are not the same initially. However, as the ligand molecules move back and forth, they reach a point where the concentration on both sides remains constant because the movement in both directions is equal.
What is the equilibrium binding constant?
By measuring the concentration of the ligand on both sides of the membrane at equilibrium, scientists can determine how strongly the ligand is binding to the macromolecule. The difference in concentrations between the two sides of the membrane provides valuable information about the interaction between the ligand and the macromolecule. This data helps scientists calculate the equilibrium binding constants, which quantify the strength of the bond between the ligand and the macromolecule.
What are colligative properties?
Colligative properties are characteristics of solutions that change when you add something to the liquid. These changes depend on how much of that added substance (like salt or sugar) is in the liquid, rather than the specific type of substance.
Colligative properties refer to the changes in properties of a solvent (such as freezing point, boiling point, vapor pressure, and osmotic pressure) when a solute is added to it. These properties are explained by the principle of equalizing chemical potential across phases.
Colligative properties are properties of solutions that depend on the number of solute particles, not their identity. These include freezing-point lowering, boiling-point elevation, vapor-pressure lowering, and osmotic pressure increase.
