Body Fluid Compartments and Membrane Transport

Flashcards covering body fluid distribution, ion concentrations, and mechanisms of cell membrane transport based on lecture notes.

Total Body Water (TBW)

The total amount of water in the body, representing $60\%$ of total body weight (BW).

IntraCellular Fluid (ICF)

The fluid contained within cells, making up $40\%$ of total body weight (BW).

ExtraCellular Fluid (ECF)

The fluid outside of cells, making up $20\%$ of total body weight (BW).

Interstitial Fluid

Fluid bathing or located between cells, comprising $16\%$ of BW; it originates from plasma leaked by capillaries.

Plasma

The fluid portion of blood contained within capillaries, representing $4\%$ of total body weight (BW).

Blood Volume

The total volume of blood in the body, ranging from $6-8\%$ of body weight, with an average of $\approx 70\,mL/kg$ BW.

Equivalent

The amount of charged solute, calculated by multiplying the number of moles of solute by its valence (charge).

Osmole

The number of particles into which a solute dissociates in solution, contributing to osmotic pressure.

Osmolarity

The concentration of a solution expressed as osmoles per liter ($Osm/L$) or milliosmoles per liter ($mOsm/L$).

pH Formula

$pH = -\log[H^{+}]$; it expresses hydrogen ion concentration and is modulated by the kidneys and lungs.

Electro neutrality

The principle that each body fluid compartment has an equal concentration of cations ($\text{+}$) and anions ($\text{-}$).

Major ECF Cation and Anions

The dominant cation is $Na^{+}$, and the dominant anions are $Cl^{-}$ and $HCO_3^{-}$.

Major ICF Cation and Anions

The dominant cation is $K^{+}$, and the dominant anions are proteins and organic phosphates like $ATP$.

Normal Osmolarity

The standard concentration level for body fluids, measured at $290-300\,mOsm/L$.

Phospholipid Bilayer

An amphipathic structure with polar, water-soluble glycerol heads and non-polar, lipid-soluble fatty acid (FA) tails.

Integral Proteins

Transmembrane proteins that can serve as hormone or neurotransmitter receptors, pores, and ion channels.

Simple Diffusion

A form of passive transport that moves solutes down a gradient without energy or carrier proteins.

Facilitated Diffusion

Passive transport down a gradient that requires a carrier protein but no energy; it is limited by saturation of carrier proteins.

Partition Coefficient

A factor in simple diffusion describing the lipid solubility of a solute; higher solubility leads to a faster diffusion rate.

Diffusion Coefficient

A factor in simple diffusion based on the size of the solute and viscosity of the solution; small size and nonviscous solutions result in faster diffusion.

Stereospecificity

A feature of carrier-mediated transport where binding sites are specific to isomers, such as transporting $D\text{-glucose}$ but not $L\text{-glucose}$.

GLUT4 Transporter

An insulin-responsive transporter in skeletal and adipose tissue that facilitates the diffusion of glucose into cells.

Primary Active Transport

Movement of solutes against a concentration gradient requiring a carrier and the direct use of energy from $ATP$.

Na/K ATPase Pump

A primary active transporter present in all cell membranes that moves $3Na^{+}$ out to the ECF and $2K^{+}$ into the ICF.

Cardiac Glycosides

A class of drugs including digoxin, ouabain, and oleandrin that inhibit the $Na/K$ ATPase pump.

PMCA (Plasma-membrane Ca2+ ATPase)

A primary active transport pump that moves $Ca^{2+}$ out of the cell into the ECF.

SERCA (Sarcoplasmic and Endoplasmic Reticulum Ca2+ ATPase)

A primary active transport pump that moves $Ca^{2+}$ from the cytoplasm into the sarcoplasmic reticulum or endoplasmic reticulum.

H/K ATPase Pump

A primary active transporter in parietal cells of gastric mucosa that moves $H^{+}$ into the lumen and $K^{+}$ into the ICF; inhibited by omeprazole.

Secondary Active Transport

Transport that moves solutes against a gradient by indirectly using energy derived from the sodium ($Na^{+}$) gradient.

Co-transport (Symport)

A type of secondary active transport where all solutes move in the same direction, such as the $Na^{+}\text{/glucose}$ co-transporter (SGLT1).

Antiport (Counter Transport)

A type of secondary active transport where solutes move in opposite directions, such as $Ca^{2+}\text{/Na}^{+}$ exchange and $Na^{+}\text{/H}^{+}$ exchange.