Membrane Potential and Cell Transport Mechanisms

Vocabulary flashcards covering resting membrane potential, membrane structure, active and passive transport mechanisms, and vesicular transport based on lecture notes.

Resting Membrane Potential (RMP)

An electrical potential across the cell membrane that is always negative, measuring $-70\,\text{mV}$ in neurons.

Intracellular and Extracellular Ion Concentrations (RMP)

At rest, inside the cell $[Na^+]$ is low and $[K^+]$ is high; outside the cell $[Na^+]$ is high and $[K^+]$ is low.

Factors Maintaining RMP

Resting membrane potential is maintained by 1. the $Na^+/K^+$ pump, 2. negatively charged proteins inside the cell, and 3. leaky $K^+$ channels that allow $K^+$ to diffuse out of the cell because they are more numerous than $Na^+$ leaky channels.

Phospholipids

Amphipathic molecules consisting of one polar head and two non-polar tails that make up the cell membrane bilayer.

Peripheral Membrane Proteins

Membrane proteins attached to the outer or inner surface of the cell membrane.

Integral Membrane Proteins

Membrane proteins embedded within the cell membrane that have both hydrophobic and hydrophilic regions, functioning in transport or as cell surface receptors.

Passive Transport

Transport mechanism that does not require energy, where molecules move down their concentration gradient via diffusion.

Facilitated Diffusion

Passive movement of molecules across the cell membrane using a channel (for ions) or a carrier (for small polar molecules like glucose).

Active Transport

Transport mechanism that requires energy (most often provided as ATP), moving molecules against their concentration gradient.

Primary Active Transport

A type of active transport that directly involves and uses ATP to move molecules against their concentration gradient.

Sodium-Potassium Pump ($Na^+/K^+$ ATPase)

An example of primary active transport that uses ATP to pump $3\,Na^+$ out of the cell and $2\,K^+$ into the cell against their concentration gradients.

Secondary Active Transport

A type of active transport that uses no direct ATP, but is provided energy by another molecule moving down its concentration gradient.

Symport

A type of secondary active transport cotransporter where $Na^+$ moves into the cell down its concentration gradient to provide energy for glucose to move into the cell against its concentration gradient.

Antiport

A type of secondary active transport exchanger where $Na^+$ moves into the cell down its concentration gradient to provide energy for $H^+$ to move out of the cell against its concentration gradient.

Acidity ($H^+$ Ions)

Acidity determined by $H^+$ ions, where more $H^+$ ions make a solution more acidic and fewer $H^+$ ions make it more basic.

Vesicular Transport

A form of active transport that uses vesicles to transport large molecules across the membrane.

Exocytosis

A form of active vesicular transport where large molecules packaged in vesicles fuse with the plasma membrane and release their contents into the extracellular space, such as neurons releasing neurotransmitters.

Endocytosis

A form of active vesicular transport where large extracellular molecules are surrounded by extensions of the cell membrane, which pinches off to enclose the molecules in a vesicle.

Phagocytosis

An example of endocytosis referred to as cellular eating.

Low Density Lipoproteins (LDL)

Lipoproteins referred to as bad cholesterol.