Protein Binding, Osmosis, and Body Fluids (Physiology)

A comprehensive set of practice flashcards covering protein binding (specificity, affinity, Keq, Kd, inhibitors, agonists/antagonists), IV fluid pharmacology (osmolarity, tonicity, penetrating vs nonpenetrating solutes, calculation steps), body fluid compartments (ICF/ECF, plasma, interstitial fluid), osmosis and osmolarity concepts, and foundational tissue and membrane physiology (epithelial/connective tissues, CAMs, ECM, resting membrane potential, Nernst and GHK equations).

What is specificity in protein–ligand binding?

The ability of a protein to bind to a particular ligand or to a group of closely related ligands.

What is required for ligand binding besides specificity?

Molecular complementarity, often with an induced-fit interaction between protein and ligand.

What does affinity refer to in protein–ligand interactions?

The degree to which a protein remains attached to a ligand.

What does equilibrium mean in protein-binding reactions?

The rate of binding equals the rate of unbinding (dynamic balance).

What does a high Keq indicate about ligand binding?

A strong tendency for the ligand and protein to form the bound complex (high affinity).

What does a large Kd indicate about ligand binding?

Weak affinity; a larger proportion of ligand and protein remain unbound at equilibrium.

How are Keq and Kd related?

They are inversely related; a high Keq corresponds to a low Kd.

Which implies stronger binding, high Keq or low Kd?

High Keq and low Kd both indicate strong binding between protein and ligand.

How do competitive and allosteric inhibitors differ in where they bind?

Competitive inhibitors bind at the active site; allosteric inhibitors bind at a different (allosteric) site.

What is the difference between an agonist and an antagonist?

An agonist increases receptor activity; an antagonist decreases activity or blocks it.

What is an inhibitor in enzyme–ligand chemistry?

A molecule that reduces the rate of enzyme activity or receptor activation, either by competitive or allosteric mechanisms.

Where does a competitive inhibitor bind?

At the enzyme’s active site (the same site as the substrate).

Where does an allosteric inhibitor bind?

At an allosteric site away from the active site, changing enzyme/receptor activity.

What does 'saturation' mean in receptor–ligand binding?

All receptors are occupied; adding more ligand does not increase the response.

What are the two major fluid compartments in the body?

Intracellular fluid (ICF) and extracellular fluid (ECF).

How is extracellular fluid subdivided?

Into plasma (intravascular) and interstitial fluid.

What drives water movement during osmosis?

A solute concentration gradient across a semipermeable membrane.

What is osmotic pressure?

The pressure required to oppose osmosis.

What is osmolarity?

The number of osmotically active particles per liter of solution.

What is osmolality?

Osmolarity expressed per kilogram of solvent; practically interchangeable in physiology.

Which solutes are penetrating versus nonpenetrating?

Penetrating solutes (e.g., glucose, urea) cross membranes; nonpenetrating solutes (e.g., NaCl) largely do not.

In IV calculations, what is the recommended first step?

Work the total body column by adding nonpenetrating solutes and volume; ignore penetrating solutes until later steps.

How are IV solutions categorized in Table 5.5?

By osmolarity and tonicity (isosmotic, hyperosmotic, isotonic, hypotonic, etc.).

What is tonicity?

The effect of a solution on cell volume due to nonpenetrating solutes; hypertonic draws water out, hypotonic causes swelling.

How do penetrating solutes affect tonicity versus osmolarity?

Penetrating solutes can alter osmolarity but may not change tonicity if they distribute evenly between ECF and ICF.

What is the basal lamina?

The basement membrane secreted by epithelial cells that anchors epithelia to underlying tissue.

What is lumen?

The inside space of a tubular structure; some lumens are considered outside the body.

What are the five epithelial tissue types?

Secretory, Protective, Exchange, Ciliated, and Transport epithelia.

What are the four basic tissue types?

Epithelial, Connective, Muscle, and Nerve tissues.

What are CAMs and give examples?

Cell adhesion molecules; examples include Cadherins, Integrins, Immunoglobulin superfamily CAMs, and Selectins.

What are the three components of connective tissue?

Ground substance (ECM), cells (e.g., fibroblasts, blasts, cytes), and matrix fibers (collagen, elastin, fibrillin, fibronectin).

What does the extracellular matrix (ECM) consist of broadly?

Proteoglycans and insoluble protein fibers (e.g., collagen, fibronectin, laminin) surrounding cells.

Which tissues are excitable?

Muscle tissue (excitable for contraction) and neural tissue (neurons are excitable).

What creates the resting membrane potential?

Ion gradients and selective membrane permeability, largely due to K+ leak channels and Na+/K+ ATPase activity.

What are the typical equilibrium potentials for K+ and Na+?

K+ ~ -90 mV; Na+ ~ +35 mV, illustrating their opposing gradients.

What equation is used to calculate the equilibrium potential for a single ion?

The Nernst equation.

What equation estimates membrane potential when multiple ions contribute?

The Goldman–Hodgkin–Katz (GHK) equation.

What happens when K+ channels open in a resting cell?

K+ ions leave the cell, making the inside more negative (hyperpolarization).

What is the electrochemical gradient?

The combined influence of concentration (chemical) gradient and electrical gradient on ion movement.

What is the purpose of the Goldman–Hodgkin–Katz equation?

To estimate the actual resting membrane potential when multiple ions contribute.

How do ions move when the membrane is permeable to K+ and Na+ differently?

Movement is governed by both concentration and electrical gradients, creating the electrochemical gradient.