Cell Structure and Membranes Flashcards

Vocabulary practice flashcards generated from lecture material on cell structure, membrane dynamics, transport mechanisms, cytoskeleton, and organelles.

Cell Theory

A foundational biological principle stating that cells are the fundamental units of life, all living organisms are composed of cells, and all cells come from preexisting cells.

Fluid Mosaic Model

A structural model of cell membranes where lipids and proteins move laterally through a bilayer composed of hydrophilic heads and hydrophobic fatty acid tails.

Integral Membrane Proteins

Proteins that are at least partly embedded in the phospholipid bilayer, possessing hydrophobic regions that interact with the membrane interior and hydrophilic regions that interact with aqueous environments.

Peripheral Membrane Proteins

Membrane proteins that lack hydrophobic groups and are not embedded in the phospholipid bilayer, attaching noncovalently to the membrane surface.

Glycolipid

A carbohydrate covalently attached to a lipid located on the outer surface of the cell membrane.

Selective Permeability

The characteristic of biological membranes that allows certain substances to pass through while restricting others.

Osmosis

The net movement of water across a membrane from a region of lower solute concentration to a region of higher solute concentration.

Tonicity

The relative concentration of solutes on either side of a membrane that determines the direction and extent of net water movement.

Turgor Pressure

Internal pressure against a cell wall caused by water uptake, which prevents further water from entering the cell once built up.

Aquaporins

Transmembrane channel proteins that specifically facilitate the rapid movement of water molecules across biological membranes.

Primary Active Transport

A transport mechanism across membranes that directly uses energy from ATP hydrolysis to move substances against their concentration gradient.

Sodium-Potassium Pump

A primary active transport protein that hydrolyzes ATP to export three $\text{Na}^+$ ions out of the cell and import two $\text{K}^+$ ions into the cell.

Secondary Active Transport

A transport mechanism that uses energy stored in an ion concentration gradient, established by primary active transport, to move another substance against its concentration gradient.

Exocytosis

A process in eukaryotic cells where secretory vesicles migrate to and fuse with the cell membrane to release large molecules outside the cell.

Phagocytosis

A specialized form of endocytosis where a cell engulfs a large particle or another cell, forming a food vesicle or phagosome that typically fuses with a lysosome.

Receptor-Mediated Endocytosis

A selective mechanism by which specific large molecules bind to surface receptors and enter eukaryotic cells via clathrin-coated pits.

Clathrin

A protein that coats the cytoplasmic side of the cell membrane at a coated pit, providing structural strength to the pit and the resulting vesicle in receptor-mediated endocytosis.

Microfilaments

Cytoskeletal filaments made of actin polymers that exhibit dynamic instability and assist in maintaining cell shape, cytoplasmic streaming, and muscle contraction.

Microtubules

Long, hollow cylindrical cytoskeletal structures composed of $\alpha\text{-tubulin}$ and $\beta\text{-tubulin}$ dimers that serve as an internal framework and tracks for motor proteins.

Dynamic Instability

The property of microfilaments and microtubules allowing them to rapidly shorten or lengthen through detachment or assembly of subunits.

Extracellular Matrix

A network of collagen and gel-like proteoglycans surrounding animal cells that holds cells together, filters materials, and helps orient cell movements.

Tight Junctions

Interlocking protein structures between adjacent animal epithelial cells that form a quilted seal to prevent movement of dissolved materials through intercellular spaces.

Gap Junctions

Channels composed of connexins running between pores of adjacent animal cells that allow direct passage of materials and electrical signals.

Nucleoid

The region in a prokaryotic cell containing its single, circular DNA molecule.

Chloroplast

An organelle in plant cells containing thylakoid membranes and stroma that converts light energy into chemical energy to produce sugar.