Membrane Transport Flashcards

These flashcards cover the vocabulary and key concepts of membrane transport, including membrane structure, passive and active transport mechanisms, and vesicular transport as described in the lecture notes.

Phospholipid

The primary component of the lipid bilayer, making up 75% of the membrane, featuring hydrophilic heads and hydrophobic tails.

Glycocalyx

Carbohydrate molecules on the cell surface used for cell identity, forming part of the 5% carbohydrates in the plasma membrane.

Cholesterol

A lipid that makes up 10% of the plasma membrane and is responsible for membrane stability.

Integral proteins

Proteins embedded within the lipid bilayer responsible for specialized membrane functions.

Peripheral proteins

Proteins that are not embedded in the lipid bilayer but are attached to the membrane surface or filaments of the cytoskeleton.

Selectively permeable

A characteristic of the plasma membrane where the movement of substances depends on molecule size and lipid solubility.

Passive transport

A method for moving substances across the membrane that requires no ATP.

Active transport

A method for moving substances across the membrane that consumes ATP.

Concentration Gradient

The difference of solute concentration separated by a semi-permeable barrier.

Filtration

A process where blood pressure forces water and small solutes through narrow clefts in capillary walls while holding back larger particles like red blood cells.

Simple Diffusion

The movement of small, nonpolar, and lipid-soluble molecules like gases and steroid hormones down their concentration gradient.

Facilitated Diffusion

The passive movement of large or polar molecules across the membrane using shape-changing carrier proteins or channel proteins.

Leakage Channels

Channel-mediated proteins that are always open to allow the passage of small lipid-insoluble solutes.

Gated Channels

Channel proteins that open or close in response to chemical, electrical, or mechanical signals.

Osmosis

The movement of water, a polar and lipid-insoluble solvent, through the lipid bilayer or specialized aquaporins.

Aquaporins

Specific channel proteins that allow for the diffusion of water molecules across the plasma membrane.

Primary Active Transport

A process that moves solutes against electrochemical gradients by directly using energy from the hydrolysis of ATP.

Secondary Active Transport

A transport mechanism that uses energy specifically from the concentration gradient created by Primary Active transport.

$Na^+-K^+$ Pump

An important example of primary active transport that moves three cytoplasmic $Na^+$ out of the cell and binds two extracellular $K^+$ to be released inside.

Vesicular Transport

The movement of large particles, macromolecules, and fluids across the membrane through endocytosis or exocytosis.

Exocytosis

The process where a membrane-bound vesicle migrates to the plasma membrane, binds via v-SNAREs and t-SNAREs, and releases its contents to the cell exterior.

Phagocytosis

A form of endocytosis used to transport large particles into the cell via a phagosome.